Thursday (21 April) & Monday (25 April): Thursday evening saw us complete our work re: Ethanol and the Causation of a Hangover. It got a little quick towards the end of class, so on Monday I will take questions in review.
The take home message is that alcohol, as with any drug, creates significant changes to our biochemistry. There are multifacetd interactions which sum to what we term "a hangover". Vassopressin in its role as Anti-Diuretic Hormone (ADH) and Glutathione (or lack thereof) in its role to convert acetylaldehyde to acetate both play significant roles.
Congener content as well as the restoration of glutamine (as in glutamine rebound) each add to the interactions.
We then launched into Unit 4 part 2 which is simply a selection of chemical processes and specific compounds I thought might be of interest. An important process is the Fischer-Tropsch Process for the production of diesel fuel and alcohols from sawgrass, sewage and other refuse materials. I stressed that this does not get us away from a dependency upon fossil fuels, nor does it aid in dealing with the challenges of climate change - but in a world of diminishing fossil fuel supplies, it could buy us time.
We then ran through some of the chemistry surrounding neurotransmitters and hormones. This allowed me to tie into some of the work seen in student literature reviews. Finally, I attacked a myriad of compounds with some form of a benzene ring and their uses. We are up to page 125 of the notes. We will wrap up this section on Thursday, 28 April, with a discussion on NSAID pain relievers.
Monday 18 April: I need to address a little housekeeping.
1) First, if your final paper has yet to be turned in, you are losing points. Let's be clear. Your paper was due last week - and unless you had made prior arrangements, you are on your way to doing far less well than midterm grades suggested, if not, simply failing the course.
2) Secondly, you cannot present without me having read your paper in advance of that presentation. We have already begun presentations. They continue until May 5 2022. If you have been unable to present by then, you have lost the opportunity to earn 50 points, and 50 points in participation, for a total of 100 points.
3) Between your paper and your presentation, there is a total of 250 points. It's up to you. I urge you to get the work completed.
Are you very clear on this? If you have questions and/or a plan, you should engage by contacting me.
4) I have pushed the due date for the second exam back to Monday 25 April. The last day to pick up the exam is this Thursday. I am not granting extensions. If you have yet to attend class to get a copy of the exam, I urge you to come up with a plan and to engage with me and with the coursework.
I am not yelling - but in truth, I am frustrated by the lack of engagement on the part of about 20% of the class. So, let me be clear. I am not coming to your rescue. You need to rescue yourself, by engaging with me, in a plan and in a timely manner. Many of the class members have now placed themselves in the unenviable situation of having to write a research paper, and complete another exam. I worked with the schedule to avoid this. Did you?
Over the last few evenings we have completed Unit 3. Last night's focus was placed on understanding or interpretating a skeletal structural formula. A good deal of this at some level was review. We again looked at the special pigmentation of hydrangea ... from white to pink to blue. We discussed ericaceous plants (those requiring for some reason, slightly acidic soil conditions). The acidic conditions help to mobilize Al+3 and Fe+3 ions, which are required for reproductive or pigmentation issues for a number of ericaceous plants, such as hydrangea, rhododendron, holly bushes, blueberry bushes and azaleas, and even Japanese Maples.
We looked at landscaping some of these plants away from the more alkaline foundation of the house and/or the need to treat with mild acidifying agents such as peat moss, Miracid or Hollytone products. You never want the soil to be too acidic.
We touched upon plant warfare with a look at lily of the valley and its use of azetidine-2- carboxylic acid.
With Unit 3 completed we moved to Unit 4. We began with a look at 6 Reactions Which Changed the World. You can find the link under the videos section or at the bottom of page 110 of Unit 4 notes.
This set us up for a look at ethanol and its effects upon the neurotransmitter GABA. This has been designed to begin a study of ethanol and hangover. We ended the evening at the bottom of page 111. We will pick up at page 112 on Thursday.
Monday 11 April: Papers are due on Thursday!!!!! I will also have another take home exam ready for Thursday.
Tonight was a good deal of vocabulary with the intention to help with final papers. We wrapped up
Unit 2 Part 2 with a brief discussion about cleaning our pets who have tangled with skunks.
We discussed skunk spray as a mixture of at least three different stinky molecules. These molecules have various features such as thiol groups (-S-H) and disulfide bonds. We briefly discussed (oddly) volumizing shampoos and the disulfide bond and moved back to the main theme.
Tomato juice is out ... rather use a mixture of hydrogen peroxide, DAWN dishwashing fluid an baking soda. We discussed the use of hydrogen peroxide and its ability to decompose into water and oxygen gas. The baking soda catalyzes the decomposition, producing the oxygen flow which becomes reduced and thus oxidizing the skunk mixture into more soluble products.
We moved very quickly onto Unit 3. This is very much a vocabulary piece. I tried to stress an approach which allows students to blend these ideas into their final papers.
We reached page 97 of the note packet.
We discussed terms such as: molecule (molecular), molecular compound, ionic compound, ionic bond, inorganic compound and organic compound.
The stress here is on applying recognition skills, if not definitions.
Note, the following are not really "definitions" but a means to recognize and to categorize using appropriate adjectives the chemicals you come across during your research. So, to help you, some of the recognition skills include:
molecule (made with nonmetal atoms ... use your periodic table to identify metals and nonmetals)
molecular compound (two different nonmetals bonded to each other)
ionic compound (a metal cation bonded to a nonmetal anion)
ionic bond (the electrostatic attraction [+ to -] between a metal cation and nonmetal anion)
inorganic compound (a chemical species made of different elements, and lacks C-H )
organic compound (a chemical species typically having at least C-H covalent bonds)
We worked away at a number of the practice problems. Stay Cool Folks and write with questions.
Monday 4 April and Thursday 31 March: We are working our way through a rather important concept (redox) , which helps to provide a foundation as to how many chemical reactions may proceed. A great many chemical reactions (not all....but a great many), may be classified as redox.
Prior work detailed the types of elements, using the activity of valence electrons. This involved a look at examples of ground state electron configurations, as seen on copies of your Periodic Table.
At this time, the terms, oxidiation and reduction (the two portions of a redox reaction) were reintroduced. I took some time to show a second video regarding the electron transport chain. While complicated, it is important to recognize basic questions of life which we tend to dance around ... such as "Why do we need to breathe oxygen?".
We then took a look at excited electron configuration and had a moment to reinforce our work on the electromagnetic spectrum .
NOTE: (In the course of this work, we revisited electrolytes and covalent bonding leading to the production of molecules) .... Consider this: Ideas are beginning to overlap and integrate. Be aware that with every review, I go a touch more deeply into the topic. I sprial the ideas. Work to avoid becoming confused - thinking that you have heard this before. Consciously work at looking at how these topic begin to integrate and reinforce each other. And be sure to ask questions!
Okay ... back to the summary.
Once completed we contrasted the idea of an excited electron configuration with the idea of chemical oxidation.
We discussed a broad interpretation of the Octet Rule , connecting this idea to effective nuclear charge and even electronegativity. The best of these ideas is found in studying the effective nuclear charge.
Effective nuclear charge is the pull or attraction experienced by an electron for a nucleus. The concept however is difficult to quantitatively measure with the work done through our course. So, I introduced electronegativity as a means to judge the tendency to lose or gain and electron. A greater (higher value) for electronegativity indicates a tendency to gain electrons (become reduced ... due to a greater effective nuclear charge). A lesser (smaller value) for electronegativity indcicates a tendency to lose electrons (to become oxidized). Now, I have played around a bit with the use of electronegativity but it does aid in visualizing what may happend with electrons, as a bond is produced.
A great deal of time was spent on identifying the oxidized species and the reduced species of a redox reaction. The concept of a disproportionation reaction was introduced. At this point we discussed the use of the decomposition of hydrogen peroxide
Remember you may treat a chemical reaction as a before and after sort of situation when evaluating for the oxidized and reduced species.
The reactants are the "before" and the products are the "after". When trying to identify the oxidized and reduced species please remember that:
1) the answer(s) always come from the reactant side of the chemical reaction (NOT the product side).
2) it is important to record or identify the species' oxidation state (even if it is zero).
3) you should include the + or - value of that oxidation state, in your answer.
4) you do NOT need to worry about using subscripts when recording your answer.
We are up to page 81 in the notes.
Monday Monday 28 March: This evening's lecture was a continuation of our work regarding the four types of elements based upon what happens with valence electrons, in a chemical reaction.
We reached the bottom of page 68 of the notes.
In short:
Metals lose electrons (they become oxidized). Metals react primarily with nonmetals. For our course metals to not react with other metals.
Metalloids/Semimetals are found bordering the "staircase" drawn onto the Periodic Table of elements. They are an odd type of element and I simply want you to know that silicon (which is actually a poor semimetal) is used in semiconductors...
Nonmetals when reacted with metals, will gain electrons (they become reduced in charge). Now, nonmetals CAN AND DO react with other nonmetals. In these situations one of the nonmetals will be more or less oxidized and another of superior electronegativity (or even effective nuclear charge) will gain the electron. Essentially these nonmetals will end up sharing electrons, with neither nonmetal atom fully losing an electron and gaining.
Noble Gases do not make compounds as a general rule (There are a few exceptions, discovered in the early 1960s, however we are not going there ... Just stick with the "general rule"). They tend not to lose or gain electrons. They do not share ... they tend do nothing, in terms of chemical reactivity.
While discussing the Octet Rule one student asked if gaining a valence level of 8 electrons brought neutrality in terms of charge. (Great Question...)
Nope! In fact atoms give up charge neutrality to gain 8 valence electrons (or as close as is possible). That valence level of 8 electrons seems to grant a form of chemical stability.
We also attacked a big question.... Why do we require oxygen to live? The answer comes in form of the electron transport system - and I am going to try to pick that idea up on Thursday.
Okay, get your paper topics in to me. Make sure you are cool with all that practice from Unit 2 Part 1 ... I can still take questions.
Monday 21 and Thursday 24 March: Okay, I think I am getting up to speed, here is the latest summary.
Let's first begin with tasks which need to be completed:
1) Your final term paper topics are due to me by Thursday 31 March. There is a listing of past topics on the Notes page and there is a checklist of ideas to add to your paper.
2) There is an assignment re: isotopic notation still going on. I strongly encourage you to try your hand at a variety of problems found in Unit 2 Part 1. The answers are provided in the packet.
3) Lab next week, is the Candle Lab (We are not going to do the Food Lab). I am using the Candle lab as a makeup for anyone who needs it due to a missed lab. So, if you have ever missed a lab, be sure to be in attendance on your normal lab night. Everyone is invited to attend. Anyone in attendance who does not need a makeup lab, can snag bonus points. I will give a copy of the lab out on Monday.
4) This week, students should have picked up the newest note packet Unit 2 Part 2. If you do not yet have these notes, be sure to see me on Monday to get a copy.
Okay, let's look at what we have been learning.
Monday evening was all about writing/interpreting isotopic notation. It really was a recap of the work done on Thursday March 10.
Interpreting isotopic notations is a skill set that is pretty clearly outlined in the notes. Goal 4 has a visual which can help. The challenge is not the material, to my mind, but rather, the amount of material. It is difficult to keep everything in mind. Use the system found under goal 4 to help you. I repeat it frequently throughout the notes. PRACTICE WILL HELP!!!!
You must realize two things
1) When I use the term "atom", you may assume the species is 0 in overall charge. Thus the #p= #e-
2) Isotopic notations are full of synonyms. Many terms refer to the same value. (see the following)
Per the diagram under Goal 4 (page 49) you will see that the terms: Mass # = (p+n) = #of nucleons are terms which refer to a value often found in the upper left hand corner of an isotopic notation.
The terms; atomic number, #of protons, nuclear charge and # of electrons are related and these values are often found in the lower left corner of an isotopic notation.
Once completed for the term, atom, we attacked our grasp of the term "ion". The terms cation and anion were introduced.
For the work on ions, there are 3 ideas you need to grasp:
1) The term ion, implies that the number of protons and electrons are UNEQUAL. An ion has fewer or more electrons when compared to the original atom.
2) Only electrons may be added or removed to make something an ion, in reaction chemistry. The number of protons does NOT change.
3) The charge tells you what subatomic particle is in EXCESS (not what was lost / gained .... you must infer that on your own. A charge of +3 means that there are three more protons (+) than electrons, because 3 electrons were lost by the original atom . A charge of -2 means that there are two MORE electrons (-) than protons, because the original atom gained two more electrons
Again, practice is your friend ... You will find a ton of practice problems in Unit 2 Part 1, pages 49-64. That's a good deal of print dedicated to this idea. Do as many as you need.
Thursday saw us begin the new note packet (Unit 2 Part 2) with the introduction of the term, electrolytes. The term electrolytes refers to ions in water, capable of conducting an electrical current.
We spent some time discussing this idea using Gatorade, and its purposes. We blended this into a minor mention of the human nervous system working off of electrolytes. A student's question as to why / when electrolytes are provided during illness became a key idea in the class.
We got up to page 67 in the notes. The periodic table of elements was the focus. I (somewhat arbitrarily) divided the elements into four large groups, metal, nonmetal, semimetals (metalloids), and noble gases, based largely on what changes to the electron cloud occurs during a chemical reaction.
Metals lose electrons to nonmetals . Metals become oxidized
Nonmetals tend to gain electrons when reacted with metals . Nonmetals become reduced It is possible to a nonmetal to become oxidized when reacted with another nonmetal, of superior effective nuclear charge and/or electronegativity. We will see more of this during our next lecture.
Thursday 10 March: Tonight focused upon two ideas:
1) The definition of isotopes and
2) Interpreting isotopic notation
Isotopes are atoms of the same element which have much in common, and something quite differentiating.
What isotopes have in common are;
a) the same atomic number (# of protons)
b) the same letter symbol
c) the same number of electrons
and thus
d) the same chemistry as electron
However, isotopes are different in that they have a different number of neutrons and thus different mass numbers.
This led us then to work away at interpreting isotopic notation. Worked away at answering an number of questions, using the system found in Goal 4, such as:
Given a specific atom .... (examples can be found in the notes)
1) What is the atomic number?
2) What is the mass number?
3) How many protons does the atom have?
4) How many neutron does the atom have?
5) How many electrons does the atom have?
6) How many nucleons comprise the nucleus of the atom?
7) What value should we give to the nuclear charge of the atom?
8) What is the overall charge of the atom?
That wrapped the class. We will finish this portion of the unit upon our return from break. Stay safe, see you soon.
Monday 7 March: We put a wrap on Unit 1, with an application of the electromagnetic spectrum as energy (capable of doing work).
That application was transition lenses and how UV light of the EMS broke a particular C - O bond in a dye molecule found in polycarbanate lenses. When UV light breaks the bond, the molecule increases in its number of double bonds. Molecules with a greater number of double bonds tend to absorb in the longer wavelengths of light, thus darkening the lenses.
We moved quickly to Unit 2 notes. We went through the 6 major goals of the note packet. In doing so, the definitions of atom, subatomic particle, and ion were given out.
It is imperative that students understand that when I use the term atom, the assumption is that the overall charge is zero (0). The number of protons (positive charge) MUST be equal to the number of electrons (negative charge).
Stress was then placed upon understanding the primary structure of the atom.
1) The nucleus is made of protons and neutron, as a general rule.
2) Protons are positive in charge. Since protons are the only charged subatomic particle of the nucleus
they make the nucleus positive.
3) Neutrons are neutral in charge
4) Electrons, found in the electron cloud beyond the nucleus are the fundamental unit of negative charge. Thus, they make the electron cloud neutral.
We briefly attacked why electrons do not fall into the nucleus - but the focus was always returned to an atom having an equal number of protons and electrons.
We then compared the meaning of the term atom to that of ion. The term ion is used to describe a chemical species with an UNEQUAL number of protons and neutrons. We will learn all about the Concept of Charge (Big Idea #3) on Thursday.
The means of interpreting an isotopic charge was then studied. This idea will take some more time, and we will revisit it on Thursday, as well.
Students were asked to complete the defintions for the terms found under Goal #1 for this unit. It would be quite helpful should everyone complete that work.
We moved through and completed the notes/readings on page 42.
Thursday 3 March: This evening's lecture tried to build upon our work regarding the electromagnetic spectrum.
The class members were asked to focus upon the common threads woven through the electromagnetic spectrum.
We reviewed some of the basic properties from the other night. Those common threads include;
1) The wave of any energy on the EMS is more or less a sinusoidal wave (as opposed to a sound wave which is described as a longitudinal wave)
2) Each wave can be described with the terms; wavelength and frequency. The greater the wavelength the smaller the frequency and conversely, the smaller the wavelength the greater the frequency.
3) Each of the types of electromagnetic energy travel at the speed of light. We discussed the concept of a light year being a distance (not a unit of time). We discussed that as we gaze at the stars, we are witnessing a long past history, as it has taken centuries for some of that light to reach us here on Earth.
We discussed television and radio signals from the 1950s which are now leaving our solar system. We took a quick look at the Very Large Array (VLA) and its purpose.
The above were mentioned on Monday, but reviewed and developed a bit more during Thursday's lecture.
The big take home message from Thursday however, was another common thread - and a very important one at that. It did not so much describe the wave but rather spoke to the origin of the energy.
That origin is found in the movement of electrons from high(er) energy levels to low(er) energy levels in an atom.
The type of electromagentic energy released by the electron(s) of an atom depends upon the change in energy an electron undergoes as it moves from a greater to lesser energy state.
Per the Law of the Conservation of Matter and Energy, the change in potential energy of an electron can not just disappear - but it can be converted into a form of kinetic energy - such as electromagnetic spectrum energy.
This is very important to recognize, as it links infrared energy to light energy to radio waves. The source of these energy waves is the same ....the movement of electrons and the conversion of lost potential energy to another form.
We then focused attention upon the Subtractive Theory of Color, in an attempt to bring in an everyday application to what we encounter. We can also look at the color of the sky and water, in terms of the absorption of certain wavelengths of the electromagnetic spectrum and the reflection of others. We see the colors reflected.
We took some time to look at "why plants are often green" and why leaves change color in the Autumn. We looked at the hypothesis that the anthocyanins (reds/purples) are most likely a protective measure limiting damage to the leaf due to continued exposure to sun, in the absence of chlorophyll. This is one reason why you might find a leaf with a reddish surface (facing the sun) while the underside of the leaf is more yellow/orange.
The take home exam was handed out. It is due Thursday 10 March 2022, in class.
Summary for 24 and 28 February: On Thursday, a new note packet was given out, as we are just about done with the current one. So, be sure to grab a copy during the next class, if you were absent.
On Thursday 24 February, students were asked to create their own summary of the class, for bonus points. Thus, I delayed the publication of a summary of that night. Now, I have included a summary below.
We are just about done with energy. This work has focused upon three ideas;
1) potential energy as chemical energy
2) the conversion of potential energy to kinetic energy
3) the expression of kinetic energy in terms of the electromagentic spectrum
Some of the "everyday applications" used to help bring relavance to these ideas are;
1) the connection of changes in / conversion of potential energy and climate change, using infrared active molecules such as carbon dioxide and water.
2) the relationship between the various forms of electromagnetic energy and the changes in potential energy of electrons; such as "heat", ultraviolet tanning, visible light and microwaves.
Thursday 24 February, saw the lecture focus upon in visuals from a video clip demonstrating rotational, translational and vibratory motions associated with molecules. The clip can be found in your notes, on page 31.
We focused upon the vibratory (vibrational) motions of bond stretching and bending. Bond stretching takes on a very special position as we blended climate change, energy conversion and potential energy.
In terms of our work on climated change, we saw that infrared molecules such as carbon dioxide can absorb energy and undergo bond stretching (but no breakage) . Bond stretching represents an increase in potential energy. As the bonds return from a stretched configuration to a less stretched configuration, the potential energy decreases, and is often converted into some form of infrared energy, radiating back into the atmosphere of Earth.
This is a terrific example as to the convergence of big idea #1 (The Law of the Conservation of Matter and Energy) and big idea #2 (Potential Energy).
The lecture on Monday, 28 February, picked up on this conversation and expanded it to a more detailed investigation of the electromagnetic spectrum (EMS).
The EMS is associated with transitions in energy (higher to lower) of the electrons of a chemical species.
As electrons transition from higher levels of energy to lower energy levels, the difference in energy states is converted into some form of electromagnetic spectral energy, such as visible light, microwaves, radio waves, ultraviolet waves, x-rays, and infrared energy.
We spent some time explaining the relationship between the wavelenght of a wave. For instance we discussed how x-rays can cause damage to tissue, because the size of the wave and the size of covalent bonds can "match up". We then took a look at a video of "Galloping Gurdy" (click for link), and used this event as a metaphor for what may happen with matching frequencies of energy.... such as bonds and EMS.
We also did some group work focused upon the movement of energy from high(er) to low(er) levels. This understanding helps to refine the conception of such ideas as a draft in a house. Importantly, this idea can also help realign and/or reinforce one's understanding that we are the "hottest thing in the environment". Hence a bag of ice put to a swelling ankle, is heated up by our body, as the energy moves from high to low. There is no such thing as "cold energy".
We investigated what we mean by temperature (average kinetic energy), how a thermometer works and the definition of radiation. Not all radiation is nuclear radiation ... remember that!
Students were asked to use the link found at the bottom of page 36 to review the video which explains why plants are green.
Thursday 17 February: The work centered around energy. One idea was central and it was accompanied by a smaller issue. The central idea was about potential energy and the smaller issue dealt with the conversion of potential energy to kinetic energy (primarily in the form of thermal/infrared energy ... what most folks somewhat erroneously call, heat)
With Thursday's lecture, we essentially have covered Big Ideas 1 and 2. A big idea is one of those overarching pieces of theory we can use over and over again to explain chemical phenomena.
Big idea 1 is the Law of the Conservation of Matter and Energy. I mean, let's face it...I haven't shut up about it.
Well Big Idea 2 , from my point of view, is all about Potential Energy.
Potential energy strikes at the very heart of our study of chemistry. Those covalent bonds introduced in the Covid work, are chemical energy and that is a form of potential energy. And bonding is so important when we start talking chemistry.
Per our notes potential energy is all about the distance or postion between objects relative to some assumed standard.
This led to any number of metaphors and examples.
In terms of chemistry I tried to develop an understanding that the conversation must be linked to the law of the conservation of matter and energy. As potential energy decreases, that energy must "go somewhere" and very often it is converted into a form of kinetic energy, such as heat.
And, for this part of the idea of potential energy we really worked at understanding the physical aspect of molecules moving away or closer to each other.
We then moved to understanding the valence electrons as those with the greater amount of potential energy relative to inner electrons.
Finally, we moved to making bonds and breaking bonds. To make a bond, species must decrease their potential energy. To break a bond, the potential energy must be increased. Remember I used the model of a pen and pen cap to help with that idea.
Anyway - we started first with the physical ascpects - such as phase changes and how they apply to our life. So here we ago in this review ....
Gaseous water vapor has a greater potential energy than liquid water. Hence as gaseous water vapor (like that which can be produced during a hot shower), heats the surrounding air as it condenses into liquid water on a mirror.
There is a "positional energy" between the molecules of water in the gas phase. As the water vapor condenses, the molecules of water come closer together. Their position relative to each other, decreases. This decrease signifies a decrease in potential energy. That energy must go somewhere and by drawing upon our grasp of the law of the conservation of matter and energy (in that energy can be transferred and/or converted to other forms), that decrease in potential energy is converted into some sort of kinetic energy. We will see this connect more specifically as we study the electromagnetic spectrum.
But some were skeptical with a warming bathroom as the shower ran - because when we get out, often we are cold. Well that is another aspect of potential energy , very much akin to sweating.
We must remember that we are the hottest thing in the room, more often than not. With water on our skin (whether due to a shower or perspiration), our body is like a stove. The energy of our body is used to heat up the water and increase that water's potential energy. As the potential energy of the water is increased by the energy of our body, the water molecules drift farther from each other .... You see, that heat energy coming from us is converted to potential energy. The outcome is that the water is evaporated into the atmosphere as a gas, and the increased (potential) energy experienced by the water, comes from us! Thus this is a cooling process... as we lose energy to the water.
This was made clearer with the less-than-optimal example of falling into cold water. Our body immediately tries to heat all that water up! Energy moves from higher levels to lower levels and we are the hottest thing around!
Water on our skin is not absorbed, rather the energy of our body is used to evaporate that water away, via our superior (heat or infrared energy) being converted to potential energy of the water.
This is one reason why if the atmospheric temperature is SUPERIOR to our body temperature, we cannot cool down. We are, in this case, not the hottest thing around. If we continue to work out or play a sport in such an environment, our body stuggles to maintain a reasonable, steady, internal temperature. This is a time for worry.
Once we wrapped up this type of work regarding phase changes, we moved onto the "bow and arrow" demo (calm down if you weren't there ....ask someone) . From this we could begin to develop an understanding that the outer electrons of an atom had greater energy than the inner electrons, as a rule.
Then we spoke a little about bonding.
The class wrapped up by students answering three questions:
What was the central idea tonight?
What did you learn about that central idea?
What example or applications apply to that central idea?
The cental idea seemed to include:
Learning included:
Examples/ Applications included:
Not a bad evening's work my friends! Nicely done!
I will see you all next Thursday. There is no lab on Thursday, as there was no lab on Monday!
Monday 14 February: Sorry for the slow update - but I am back online! Monday night wrapped up the first part of Unit 1. Within the context of matter and energy , we have been covering quite a bit of material. We ended at page 28 - the last page of the first set of notes.
Monday's lecture focused upon the end pieces of what we term as, mixtures. It then covered means of identifying an exothermic or endothermic change as well as chemical reactions.
In terms of wrapping up mixtures, we took a look at hard water. The term, hard water, is often applied to samples of water with higher concentrations of Ca+2 ion and Mg+2 ion. These ions interfer with suds formation of soaps and shampoos. They form precipitates which can form deposits on pipes and soap scum in the sink and bathtub. We also touched upon "soft water".... or rather water so lacking in the above ions that rinsing soap off of ourselves can prove to be difficult.
Exothermic changes are those in which the activity of the chemicals in question releases more energy into the environment of the chemicals (the surrounding air or water, if in a beaker). There is a net release of energy.
On paper, the energy signature (kJ) of an exothermic change will be on the product side of a reaction equation.
The classic example is a fire. More energy is generated (released) by a fire than is absorbed when starting a fire. The energy of a match is utterly overwhelmed by the energy released as a fire continues on its own, after activation.
While fire is the classic example, a common sort of exothermic change is a cooling process. What may confuse students is that freezing or condensation must be classified as exothermic.
Huh? Freezing is not like a fire! That appears to be a bit counterintuitive - yet, if you look at the definition, in which energy must be released by the chemicals in question to the environment, it can make a good deal of sense.
Cooling is exothermic. What must be true about any cooling process? ... Yep, the overall termperature must decrease. Energy MUST LEAVE THE CHEMICALS and move to the environment. (Energy moves from areas of high concentration to lower concentration.)
Hence, in a cooling process, such as freezing water to ice, energy must exit the water system and must, therefore move to the surrounding environment. Hence, freezing is exothermic!
The converse (as in the opposite of) to an exothermic change is an endothermic change. This refers to a system in which the chemicals in question absorb more energy than is released. Heating up water from 15C to 75C is and endothermic process. Much more energy is being absorbed by the water, as it heats, than is released.
With these energy exchange issues completed we moved on to a study of chemical reactions.
There are two skills I hoped to have developed.
1) I wanted class members to be able to identify a chemical reaction when they were given a test.
2) I also wanted class members to be able to identify a chemical reaction in their life.
The skills are a bit different. The first is the easiest. A chemical reaction will have new bonds produced. On a test, we can see this as a rearrangement of the element symbols. The notes have multiple examples.
The second addresses my desire for this class to be truely about "everyday chemistry". To identify a chemical reaction in "real life" you may wish to consider finding 2 or 3 of the following visual clues.
a) the production of a new solid
b) the production of a new gas, which results in a release of bubbles
c) the production of a new liquid (tough)
d) a bold change in color
e) an energy change (the release of energy or the absorption of energy).
For instance, it is reasonable to classify a wood fire as a chemical reaction. New solids (ash) are produced. New gases can be smelled as wood combusts. Clearly there is an energy change.
Rusting of iron is also a reasonable example. Iron turns to iron oxide (a different, more brittle, flakier solid). There is a change in color, as iron oxide (rust) tends to be anywhere in color, from yellow, to black, to reddish brown.
Okay, be sure to have the problems up through page 28 completed. Write with questions and/or bring in your questions to class.
Thursday 10 February: Last evening's lecture was all about mixtures. I thought we would get into energy but, these things happen. There was the main idea regarding mixtures but there was also, a smaller yet important sub-theme which dealt with the strength of a chemical bond, like the one found between the atoms of hydrogen and oxygen in a water molecule.
We reviewed that the elements which comprise a compound tend to have different properties from the compound they make.
However, a mixture tends to exhibit the independent properties of the components used to make the mixture. For instance, if you were to add sweetened ice tea mix to a glass of water - no chemical reaction occurs. Rather you just make a mixture.
Using the word "dissolve" is a good clue that you have a mixture.
Other clues that you are dealing with a mixture include:
Okay, back to sweetened ice tea ... The sugar in that mix, is still sweet tasting. The water is still a fluid, the color is consistent. The individual properties of the components of a mixture don't really change all that much.
We spoke about the Earth's atmosphere's composition and the content of our inhaled and exhaled breath. Yes, we do breath out a fair amount of oxygen .
We took a quick look at the use of oil in our society. Yep, we are absolutely bathed in the stuff, as it were. We need oil for any number of molecules used to make a host of products. One of the challenges for the future is conserving oil for our production means and balancing this with the combustion of fossil fuels (which we now know.... are not from "rocks" or fossils, in the strictest sense of the term).
We also looked at the work of Alice Ball, using the SciShow video found
at: https://www.youtube.com/watch?reload=9&v=dymJcBkGlbs&feature=youtu.be
Her work was absolutely critical in developing an effective treatment for leprosy, prior to the development of antibiotics. Her techniques also shadow our own lab work in that we will perform a saponification as well as an esterification! Remember, we are all about making connections between our work and the "everyday world".
Thus, jumping off of Ms. Ball's amazing work, we can again see that mixtures can be separated via a number of means, some use chemical reactions while others use physical means such as filtration, boiling, chromatography etc...
This last thread led to a detailed discussion of our sub-theme regarding the strength of a chemical bond. We used the idea of boiling water from liquid to its gas phase. Using the diagram at the top of page 24,
I tried to emphasize the energy requirements to break a bond. The energy required to separate a mixture is often much lower.
So, think about boiling water. Do you realize that we simply move the molecules of water so far away from each other, with the energy added to the sample of water, that we form the liquid into a gas? There is just a change in phase or state of matter.
We DO NOT break the bonds between H-O and produce H2 and O2. Hear that again: We DO NOT produce hydrogen gas and oxygen gas when we boil water. We can infer this because there are no explosions. We know that hydrogen gas burns and oxygen supports that combustion (recall the Hindenberg).
Forming these gases DOES NOT occur when we boil water. Thus the conclusion is that what is produced is water vapor. The molecules are intact, the bonds are not broken.
Now imagine how much energy is in that boiling water! That amount of energy is INSUFFICIENT to break the chemical bond between H and O! Yet, chemical reactions which do have bonds breaking and making occur in our bodies every second of our lives. This is really amazing! How does this all happen? Well, those are topics for future lectures.
Students were asked to grab a few notes on pages 25 and 26 using the online services. Additionally folks with well water may wish to bring in a sample of that water for testing next week. Be sure your lab is read.
Write with questions.
Monday 7 February: Tonight's work was pretty straight forward. The terms; substance, element, compound, mixture, homogeneous and heterogeneous, were introduced formally. We ended the evening on page 24 of the notes.
This week's lab, chromatography, is all about the separation of a mixture, so lecture and lab are still meshing.
Okay, so here is a brief review...
There are essentially 2 overarching terms for us to use, when trying to classify a sample of matter. We can use the term Substance or the term, Mixture (but we cannot use BOTH terms as an adjective of a single sample of matter.)
For our work, we shall describe a sample either as a substance or as a mixture. Thus a sample is either a (single) substance or a physical merging of multiple substances (called a mixture).
All substances are homogeneous (uniform in composition). We can "picture" this definition by asking ourselves; "How many different types of matter do we see"? When the answer is "I see one type of matter (that is it all looks the same) ..." then we can say the matter is homogeneous.
When we see multiple different types of matter... e.g. a piece of granite, then we can describe the sample as heterogeneous. Substances must be homogeneous and mixtures may be either homogeneous or heterogeneous.
A reasonable means to think of these terms is that the terms do not imply how many types of matter there actually are - but rather, how many we "see".
Subtances my be further classifed as elements or compounds (but not both).
A sample of matter, may be an element (species which each have the same atomic number) or a sample of matter my be a compound (chemically bonded species of two or more different elements in a definite proportion). The term definite proportion lead to a discussion on subscripts. In this discussion we worked with water H2O and H2O2 (hydrogen peroxide). In water, the proportion of hydrogen to water is 2:1 in terms of atoms. In the compound hydrogen peroxide the proportion is 1:1 in terms of species.
In terms of mass the relationship of hydrogen to oxygen is 2 : 16 or 1: 8 (Don't worry how I figured that out , I am just trying to drive home a point)
For hydrogen peroxide, the relationship of hydrogen to oxygen , by mass is 2:32 or 1:16.
You see, compounds have definite proportions ...change the proportions (if possible) and you change the compound.
And then someone asked about H2 + O2 --> H2O inwhich a flammable gas, and a gas which supports combustion (burning) chemically combine to produce an utterly different product (which actually puts out many fires)
This is key about compounds. The properties of the compound may be very different from the properties of the elements which make the compound! This is not really accurate of mixtures.
Mixtures may be of varying proportions. (You might add 3 teaspoons of ice tea mix to a glass of water, or you might add only two. This is what I mean by varying proportions.) The Earth's atmosphere is a mixture of gases and fine particulate matter. Over the millenia, the percentage of oxygen has changed from upwards of 26% to 21% ....(again, a varying proportion).
You may have a small amount of salt in water (as in a estuary like the mouth of the Hudson River, where fresh river water mixes with oceanic salt water) or a much greater amount of salt in water, like the Pacific Ocean. Mixtures have variable proportions to their compositions. Or keeping with this theme, the salinity (salt content) of the Atlantic Ocean is greater than the salinity of the Pacific Ocean! You see? Even ocean waters (mixtures) can vary in their composition.
This is key about mixtures. The components of the mixture tend to maintain their individual properties! This is one of the reasons why we can separate those components using relatively simple physical methods.
Thursday will see us focus upon mixtures, (with a look at an early treatment for leprosy and a look at a barrel of oil) and then possibly move on into energy.
Take a look at the notes...write with questions.
Thursday 3 February: We are up to page 21 of the notes. We are beginning to make some headway.
Last night's lecture material centered on density as a state of compactedness of the atoms/molecules of a material. We spent some time getting comfortable with what sinks and what floats (or rises) given differences in densities. The small problem set on page 17 was important.
Once comfortable we could move on into a number of threads.
First, we worked at trying to understand why lakes / ponds freeze at the top and not the bottom. It's a good thing that they do freeze at the top because ice forming anywhere else would more than likely kill any of the vertebrate and plant life in the water!
The key is that water is really different from almost all of the other materials of which we know. You see, as most materials freeze, they become denser ... more compact.
The above is NOT true for water! Water is densest at 4C (about 1.00 g/mL), but it freezes at 0C. The natural conclusion is that 4C water is more compacted than 0C ice-water and so we could conclude that 4C water would sink through any other water, regardless of that other water's temperature.
The top layer of water is in contact with air. Let's assume that air is colder than the water. Energy will flow from the water to the air and the water will cool. As that water approaches 4C, it will sink down into the lake.
As it sinks a new layer of "surface water" is revealed and it too will cool to 4C and sink. This cycle of replacing the top layer of water, by allowing it to cool and sink, only to be replaced by a another layer of water goes on until the whole of the lake water is at 4C. (Read that again.....)
The surface water will continue to cool below 4C (assuming the air temperature is much lower). At this point that surface water (which is lower than 4 C) will be automatically LESS dense than all the water beneath it. It does NOT sink. Rather, this surface layer continues to lose energy to the air and ultimately reaches 0C (or colder) and it freezes. Ice, with its density of approximately 0.99 g/cm3 will "float" .
Now, the second thread to the conversation evolved from the actual structure of ice vs. water. As ice forms (recall water is weird), the volume expands and thus for a given mass, the density must decrease. (analyze D = M/V ... As V increases, at constant M, then D must decrease)
The question is WHY does water do this?
I took some time to discuss the distribution of partial charges across a water molecule. The oxygen of water is slightly negative and the hydrogen are partially positive. We did not discuss why...just the "is".
This means that the partially positive hydrogen of one molecule will be attracted to the slightly negative oxygen of a SECOND (different) molecule of water. There is a diagram on page 19.
(Here's where we veered off the topic of density): These partial charges exist on a lot of matter. Matter, like the blown layer in our face masks. This mid-layer of a well made face mask like an N95 or KN95 or good surgical mask has lots of charges.
Viral particles also have partial charges and the mid layer of masks traps viral particles preventing them from passing through into our respiratory system! (recall: opposite charges attract!)
We then discussed to a small degree how the virus works, and how the vaccines work to protect us.
We then wrapped it all up , and took some "wrap up" or closing notes on page 21!
And here is the big Take Home Message:
You see, the chemistry of one system can be used to help us understand the chemistry of a completely different system - because chemistry is chemistry. You may / may not be fascinated with why water-ice expands as it freezes. However, there are threads here that help us build our science (knowledge). It is how we apply these fundemental ideas that makes things different - but the chemistry is the same. Think about that.
Write with questions.
Monday 31 January: There were two ideas to grab onto in this class. The first focus was on the idea of pressure.
1) We are measuring pressure as the force exerted on the sides of a container of gas. For our work, the measurement of pressure is greatly affected by the number of interactions a gas molecule has with the sides of the container. This value is greatly affected by temperature. A hotter gas has a greater acceleration, which affects the pressure as seen in the equation P=(mass)(acceleration)/area.
2) Using our diagrams of a trapped gas trapped in a cylinder with a moveable piston we deduced that as pressure on the gas was increased, volume of the gas was decreased. We can infer that pressure was increased because the gas molecules occupy a smaller volume and interact with the sides of the container more often. Thus, we wrote down as ancillary notes, that as Volume (of a trapped gas) DECREASES, pressure exerted by that gas INCREASES.
3) The inverse is also correct: As the volume of a trapped gas is allowed to increase, pressure decreases (we must assume a constant temperature). For those from prior chemistry experience this is Boyle's Law, which expresses this inverse relationship between pressure and volume, at constant temperature.
4) But for us, we could then apply this idea (as volume decreases, pressure increases) to how we as mammals breathe! Remember, this is Everyday Chemistry, and we focus upon such applications. So check out page 13 of the notes. Only the internal pulmonary pressure changes due to compression and/or expansion of trapped gases, as the diaphragm and rib cage move.
5) We also applied the idea of pressure and the amount of gas to the atmosphere. We introduced the unit of atmospheres (or kilopascals) to associate with pressure. We used the diagram found on page 11
The second idea was working with the idea of extensive and intensive properties of matter.
Constants at a known temperature and pressure, such as melting point and density are intensive properties. We can use these intensive properties to help identify substances. (We wrote this down).
Variables such as the amount of mass, volume or length , which can be changed by simply adding "more stuff" are extensive properties.
I used the analogy (and analogies are limited, so don't be too literal), of a price for 1 tee shirt vs. the entire bill you pay when purchasing a bunch of tee shirts. The price per 1 tee shirt is like an intensive property. It is a constant per 1 shirt. The total bill changes depending upon HOW MUCH you purchase. If you buy 5 shirts or 10 shirts, the total cost changes. Thus the total cost is like an extensive property.
We kept going back to the example of an iceberg vs. an ice cube (page 14). This is an important example in terms of helping students to latch onto the ideas of extensive vs. intensive properties.
Practice problems on page 15 were assigned. (You can get the answers using this website and opening the online version of the notes (Unit 1 Part 1). Select the area near an * and change the font color.)
We then touched upon density, but we will finish that discussion on Thursday. Don't forget, A Capsule of Covid Chemistry is due on Thursday!
Write with questions!
Thursday 27 January: There are a few things to cover:
1) A new assignment was given out... A Capsule of Covid Chemistry. A link to the assignment may be found on the Guided Notes page. Hard copies are due on Thursday, 3 February. Write me with questions.
2) We are on page 10 of the note packet and student are asked to complete page 10, using the online notes. That will wrap up our work on pressure. A student asked a stellar question about what happens to a gas when put under high pressure. I altered the question just a bit by adding what might happen under extreme pressure accompanied by a drop in temperature? This led us to our first conversation about changes in phase. Then when one student raised the issue of putting a gas under high pressure without a drop in temperature, as in a car cylinder , we could talk about autoignition when mixtures containing octane are compressed! Not a bad 15 minutes there people. I was so pleased. People were engaged, risking, and asking darn fine questions, as they pursued their interests. Good on you!
3) The demo on volume went off without a hitch ... always good to see. The take home message is that liquids (like water) have a constant volume, but not a constant shape. The song, btw, was a variation of Twinkle Twinkle Little Star by W.A. Mozart.
4) We spent a fair amount of time discussing gravity . Don't forget about our 120 lbs astronaut on Earth compared to her 20 lbs on the Moon. We did a little warped space = gravity work, using a trampoline as an example. I gladly admit that I warp the fabric of space less than the planet Earth. We tossed ideas about Superman around a little bit, and no, I cannot explain the laser beams out of his eyes ...but I could reasonably stretch an explanation to flying. Toss in the possibility of a little speciation if Mars colonies become a reality . Hmm, ad hoc and stir!
5) The term weight is of value only when discussing a mass in different gravitational fields. Weight changes as gravity changes, but mass does NOT change. Our weight would change slightly were we at the Earth's equator, at the top of Mt. Everest, or Death Valley.
6) It is reasonable to suggest that Pluto is not a planet. We could infer this by comparing the weight of a student on Earth, compared to their weight on the Moon and then on Pluto. We may infer from the data derived due to the celestial bodies differing gravity, that Pluto is significantly smaller than our moon. That caused on student to ask why the moon is not a planet . Yet another nice question!
Okay, so there is a new assignment. Lab reports are due next Monday and next Thursday. Be sure to follow the Lab Report Template found in the Introductory Packet. Be sure to cite your research. If you needed to look it up, you need to cite it. Write with questions.
Monday 24 January: No big assignments were given out. I simply want to update what we have done and where we are in the notes, for students who have just dropped in and for those students who have been out. We have been working our way through the basics of vocabulary, with matter, energy, mass, volume and weight. A fair amount of time has been spent on differentiating between matter and energy ... how to tell one from the other and the rationale behind those reasons. Expect to see questions regarding the Law of the Conservation of Matter, Energy and Charge on an exam (For example: You want to be able to deal with the definition as well as a question such as #2 on page 7 of the notes) .
We worked away at the definition of mass- which under the best of circumstances is a tough one. We reached page 8 of the notes. Thursday will see us wrap up an understanding of weight and volume... Then we really hit the road!
Monday night had their first lab. The Thursday night crew will get the same lab. We also went over the locations of the exits from the lab and safety equipment: fire extinguisher, chemical shower, fire blanket, and the eye wash.
Thursday 20 January: Have the introductory packet read/reviewed in preparation of the first lecture. A hard copy will be provided in class. Be sure to spend a good amount of time reviewing the laboratory safety measures found on page 11. Be ready to ask any questions of clarification.
For your lab on either Monday (24 January) or Thursday (27 January) be sure to have the lab ALCHEMY read and prepared. Be familiar with the experiment per the introduction of the lab. Read over and familiarize yourself with the procedure and the questions.
The take home message is that alcohol, as with any drug, creates significant changes to our biochemistry. There are multifacetd interactions which sum to what we term "a hangover". Vassopressin in its role as Anti-Diuretic Hormone (ADH) and Glutathione (or lack thereof) in its role to convert acetylaldehyde to acetate both play significant roles.
Congener content as well as the restoration of glutamine (as in glutamine rebound) each add to the interactions.
We then launched into Unit 4 part 2 which is simply a selection of chemical processes and specific compounds I thought might be of interest. An important process is the Fischer-Tropsch Process for the production of diesel fuel and alcohols from sawgrass, sewage and other refuse materials. I stressed that this does not get us away from a dependency upon fossil fuels, nor does it aid in dealing with the challenges of climate change - but in a world of diminishing fossil fuel supplies, it could buy us time.
We then ran through some of the chemistry surrounding neurotransmitters and hormones. This allowed me to tie into some of the work seen in student literature reviews. Finally, I attacked a myriad of compounds with some form of a benzene ring and their uses. We are up to page 125 of the notes. We will wrap up this section on Thursday, 28 April, with a discussion on NSAID pain relievers.
Monday 18 April: I need to address a little housekeeping.
1) First, if your final paper has yet to be turned in, you are losing points. Let's be clear. Your paper was due last week - and unless you had made prior arrangements, you are on your way to doing far less well than midterm grades suggested, if not, simply failing the course.
2) Secondly, you cannot present without me having read your paper in advance of that presentation. We have already begun presentations. They continue until May 5 2022. If you have been unable to present by then, you have lost the opportunity to earn 50 points, and 50 points in participation, for a total of 100 points.
3) Between your paper and your presentation, there is a total of 250 points. It's up to you. I urge you to get the work completed.
Are you very clear on this? If you have questions and/or a plan, you should engage by contacting me.
4) I have pushed the due date for the second exam back to Monday 25 April. The last day to pick up the exam is this Thursday. I am not granting extensions. If you have yet to attend class to get a copy of the exam, I urge you to come up with a plan and to engage with me and with the coursework.
I am not yelling - but in truth, I am frustrated by the lack of engagement on the part of about 20% of the class. So, let me be clear. I am not coming to your rescue. You need to rescue yourself, by engaging with me, in a plan and in a timely manner. Many of the class members have now placed themselves in the unenviable situation of having to write a research paper, and complete another exam. I worked with the schedule to avoid this. Did you?
Over the last few evenings we have completed Unit 3. Last night's focus was placed on understanding or interpretating a skeletal structural formula. A good deal of this at some level was review. We again looked at the special pigmentation of hydrangea ... from white to pink to blue. We discussed ericaceous plants (those requiring for some reason, slightly acidic soil conditions). The acidic conditions help to mobilize Al+3 and Fe+3 ions, which are required for reproductive or pigmentation issues for a number of ericaceous plants, such as hydrangea, rhododendron, holly bushes, blueberry bushes and azaleas, and even Japanese Maples.
We looked at landscaping some of these plants away from the more alkaline foundation of the house and/or the need to treat with mild acidifying agents such as peat moss, Miracid or Hollytone products. You never want the soil to be too acidic.
We touched upon plant warfare with a look at lily of the valley and its use of azetidine-2- carboxylic acid.
With Unit 3 completed we moved to Unit 4. We began with a look at 6 Reactions Which Changed the World. You can find the link under the videos section or at the bottom of page 110 of Unit 4 notes.
This set us up for a look at ethanol and its effects upon the neurotransmitter GABA. This has been designed to begin a study of ethanol and hangover. We ended the evening at the bottom of page 111. We will pick up at page 112 on Thursday.
Monday 11 April: Papers are due on Thursday!!!!! I will also have another take home exam ready for Thursday.
Tonight was a good deal of vocabulary with the intention to help with final papers. We wrapped up
Unit 2 Part 2 with a brief discussion about cleaning our pets who have tangled with skunks.
We discussed skunk spray as a mixture of at least three different stinky molecules. These molecules have various features such as thiol groups (-S-H) and disulfide bonds. We briefly discussed (oddly) volumizing shampoos and the disulfide bond and moved back to the main theme.
Tomato juice is out ... rather use a mixture of hydrogen peroxide, DAWN dishwashing fluid an baking soda. We discussed the use of hydrogen peroxide and its ability to decompose into water and oxygen gas. The baking soda catalyzes the decomposition, producing the oxygen flow which becomes reduced and thus oxidizing the skunk mixture into more soluble products.
We moved very quickly onto Unit 3. This is very much a vocabulary piece. I tried to stress an approach which allows students to blend these ideas into their final papers.
We reached page 97 of the note packet.
We discussed terms such as: molecule (molecular), molecular compound, ionic compound, ionic bond, inorganic compound and organic compound.
The stress here is on applying recognition skills, if not definitions.
Note, the following are not really "definitions" but a means to recognize and to categorize using appropriate adjectives the chemicals you come across during your research. So, to help you, some of the recognition skills include:
molecule (made with nonmetal atoms ... use your periodic table to identify metals and nonmetals)
molecular compound (two different nonmetals bonded to each other)
ionic compound (a metal cation bonded to a nonmetal anion)
ionic bond (the electrostatic attraction [+ to -] between a metal cation and nonmetal anion)
inorganic compound (a chemical species made of different elements, and lacks C-H )
organic compound (a chemical species typically having at least C-H covalent bonds)
We worked away at a number of the practice problems. Stay Cool Folks and write with questions.
Monday 4 April and Thursday 31 March: We are working our way through a rather important concept (redox) , which helps to provide a foundation as to how many chemical reactions may proceed. A great many chemical reactions (not all....but a great many), may be classified as redox.
Prior work detailed the types of elements, using the activity of valence electrons. This involved a look at examples of ground state electron configurations, as seen on copies of your Periodic Table.
At this time, the terms, oxidiation and reduction (the two portions of a redox reaction) were reintroduced. I took some time to show a second video regarding the electron transport chain. While complicated, it is important to recognize basic questions of life which we tend to dance around ... such as "Why do we need to breathe oxygen?".
We then took a look at excited electron configuration and had a moment to reinforce our work on the electromagnetic spectrum .
NOTE: (In the course of this work, we revisited electrolytes and covalent bonding leading to the production of molecules) .... Consider this: Ideas are beginning to overlap and integrate. Be aware that with every review, I go a touch more deeply into the topic. I sprial the ideas. Work to avoid becoming confused - thinking that you have heard this before. Consciously work at looking at how these topic begin to integrate and reinforce each other. And be sure to ask questions!
Okay ... back to the summary.
Once completed we contrasted the idea of an excited electron configuration with the idea of chemical oxidation.
We discussed a broad interpretation of the Octet Rule , connecting this idea to effective nuclear charge and even electronegativity. The best of these ideas is found in studying the effective nuclear charge.
Effective nuclear charge is the pull or attraction experienced by an electron for a nucleus. The concept however is difficult to quantitatively measure with the work done through our course. So, I introduced electronegativity as a means to judge the tendency to lose or gain and electron. A greater (higher value) for electronegativity indicates a tendency to gain electrons (become reduced ... due to a greater effective nuclear charge). A lesser (smaller value) for electronegativity indcicates a tendency to lose electrons (to become oxidized). Now, I have played around a bit with the use of electronegativity but it does aid in visualizing what may happend with electrons, as a bond is produced.
A great deal of time was spent on identifying the oxidized species and the reduced species of a redox reaction. The concept of a disproportionation reaction was introduced. At this point we discussed the use of the decomposition of hydrogen peroxide
Remember you may treat a chemical reaction as a before and after sort of situation when evaluating for the oxidized and reduced species.
The reactants are the "before" and the products are the "after". When trying to identify the oxidized and reduced species please remember that:
1) the answer(s) always come from the reactant side of the chemical reaction (NOT the product side).
2) it is important to record or identify the species' oxidation state (even if it is zero).
3) you should include the + or - value of that oxidation state, in your answer.
4) you do NOT need to worry about using subscripts when recording your answer.
We are up to page 81 in the notes.
Monday Monday 28 March: This evening's lecture was a continuation of our work regarding the four types of elements based upon what happens with valence electrons, in a chemical reaction.
We reached the bottom of page 68 of the notes.
In short:
Metals lose electrons (they become oxidized). Metals react primarily with nonmetals. For our course metals to not react with other metals.
Metalloids/Semimetals are found bordering the "staircase" drawn onto the Periodic Table of elements. They are an odd type of element and I simply want you to know that silicon (which is actually a poor semimetal) is used in semiconductors...
Nonmetals when reacted with metals, will gain electrons (they become reduced in charge). Now, nonmetals CAN AND DO react with other nonmetals. In these situations one of the nonmetals will be more or less oxidized and another of superior electronegativity (or even effective nuclear charge) will gain the electron. Essentially these nonmetals will end up sharing electrons, with neither nonmetal atom fully losing an electron and gaining.
Noble Gases do not make compounds as a general rule (There are a few exceptions, discovered in the early 1960s, however we are not going there ... Just stick with the "general rule"). They tend not to lose or gain electrons. They do not share ... they tend do nothing, in terms of chemical reactivity.
While discussing the Octet Rule one student asked if gaining a valence level of 8 electrons brought neutrality in terms of charge. (Great Question...)
Nope! In fact atoms give up charge neutrality to gain 8 valence electrons (or as close as is possible). That valence level of 8 electrons seems to grant a form of chemical stability.
We also attacked a big question.... Why do we require oxygen to live? The answer comes in form of the electron transport system - and I am going to try to pick that idea up on Thursday.
Okay, get your paper topics in to me. Make sure you are cool with all that practice from Unit 2 Part 1 ... I can still take questions.
Monday 21 and Thursday 24 March: Okay, I think I am getting up to speed, here is the latest summary.
Let's first begin with tasks which need to be completed:
1) Your final term paper topics are due to me by Thursday 31 March. There is a listing of past topics on the Notes page and there is a checklist of ideas to add to your paper.
2) There is an assignment re: isotopic notation still going on. I strongly encourage you to try your hand at a variety of problems found in Unit 2 Part 1. The answers are provided in the packet.
3) Lab next week, is the Candle Lab (We are not going to do the Food Lab). I am using the Candle lab as a makeup for anyone who needs it due to a missed lab. So, if you have ever missed a lab, be sure to be in attendance on your normal lab night. Everyone is invited to attend. Anyone in attendance who does not need a makeup lab, can snag bonus points. I will give a copy of the lab out on Monday.
4) This week, students should have picked up the newest note packet Unit 2 Part 2. If you do not yet have these notes, be sure to see me on Monday to get a copy.
Okay, let's look at what we have been learning.
Monday evening was all about writing/interpreting isotopic notation. It really was a recap of the work done on Thursday March 10.
Interpreting isotopic notations is a skill set that is pretty clearly outlined in the notes. Goal 4 has a visual which can help. The challenge is not the material, to my mind, but rather, the amount of material. It is difficult to keep everything in mind. Use the system found under goal 4 to help you. I repeat it frequently throughout the notes. PRACTICE WILL HELP!!!!
You must realize two things
1) When I use the term "atom", you may assume the species is 0 in overall charge. Thus the #p= #e-
2) Isotopic notations are full of synonyms. Many terms refer to the same value. (see the following)
Per the diagram under Goal 4 (page 49) you will see that the terms: Mass # = (p+n) = #of nucleons are terms which refer to a value often found in the upper left hand corner of an isotopic notation.
The terms; atomic number, #of protons, nuclear charge and # of electrons are related and these values are often found in the lower left corner of an isotopic notation.
Once completed for the term, atom, we attacked our grasp of the term "ion". The terms cation and anion were introduced.
For the work on ions, there are 3 ideas you need to grasp:
1) The term ion, implies that the number of protons and electrons are UNEQUAL. An ion has fewer or more electrons when compared to the original atom.
2) Only electrons may be added or removed to make something an ion, in reaction chemistry. The number of protons does NOT change.
3) The charge tells you what subatomic particle is in EXCESS (not what was lost / gained .... you must infer that on your own. A charge of +3 means that there are three more protons (+) than electrons, because 3 electrons were lost by the original atom . A charge of -2 means that there are two MORE electrons (-) than protons, because the original atom gained two more electrons
Again, practice is your friend ... You will find a ton of practice problems in Unit 2 Part 1, pages 49-64. That's a good deal of print dedicated to this idea. Do as many as you need.
Thursday saw us begin the new note packet (Unit 2 Part 2) with the introduction of the term, electrolytes. The term electrolytes refers to ions in water, capable of conducting an electrical current.
We spent some time discussing this idea using Gatorade, and its purposes. We blended this into a minor mention of the human nervous system working off of electrolytes. A student's question as to why / when electrolytes are provided during illness became a key idea in the class.
We got up to page 67 in the notes. The periodic table of elements was the focus. I (somewhat arbitrarily) divided the elements into four large groups, metal, nonmetal, semimetals (metalloids), and noble gases, based largely on what changes to the electron cloud occurs during a chemical reaction.
Metals lose electrons to nonmetals . Metals become oxidized
Nonmetals tend to gain electrons when reacted with metals . Nonmetals become reduced It is possible to a nonmetal to become oxidized when reacted with another nonmetal, of superior effective nuclear charge and/or electronegativity. We will see more of this during our next lecture.
Thursday 10 March: Tonight focused upon two ideas:
1) The definition of isotopes and
2) Interpreting isotopic notation
Isotopes are atoms of the same element which have much in common, and something quite differentiating.
What isotopes have in common are;
a) the same atomic number (# of protons)
b) the same letter symbol
c) the same number of electrons
and thus
d) the same chemistry as electron
However, isotopes are different in that they have a different number of neutrons and thus different mass numbers.
This led us then to work away at interpreting isotopic notation. Worked away at answering an number of questions, using the system found in Goal 4, such as:
Given a specific atom .... (examples can be found in the notes)
1) What is the atomic number?
2) What is the mass number?
3) How many protons does the atom have?
4) How many neutron does the atom have?
5) How many electrons does the atom have?
6) How many nucleons comprise the nucleus of the atom?
7) What value should we give to the nuclear charge of the atom?
8) What is the overall charge of the atom?
That wrapped the class. We will finish this portion of the unit upon our return from break. Stay safe, see you soon.
Monday 7 March: We put a wrap on Unit 1, with an application of the electromagnetic spectrum as energy (capable of doing work).
That application was transition lenses and how UV light of the EMS broke a particular C - O bond in a dye molecule found in polycarbanate lenses. When UV light breaks the bond, the molecule increases in its number of double bonds. Molecules with a greater number of double bonds tend to absorb in the longer wavelengths of light, thus darkening the lenses.
We moved quickly to Unit 2 notes. We went through the 6 major goals of the note packet. In doing so, the definitions of atom, subatomic particle, and ion were given out.
It is imperative that students understand that when I use the term atom, the assumption is that the overall charge is zero (0). The number of protons (positive charge) MUST be equal to the number of electrons (negative charge).
Stress was then placed upon understanding the primary structure of the atom.
1) The nucleus is made of protons and neutron, as a general rule.
2) Protons are positive in charge. Since protons are the only charged subatomic particle of the nucleus
they make the nucleus positive.
3) Neutrons are neutral in charge
4) Electrons, found in the electron cloud beyond the nucleus are the fundamental unit of negative charge. Thus, they make the electron cloud neutral.
We briefly attacked why electrons do not fall into the nucleus - but the focus was always returned to an atom having an equal number of protons and electrons.
We then compared the meaning of the term atom to that of ion. The term ion is used to describe a chemical species with an UNEQUAL number of protons and neutrons. We will learn all about the Concept of Charge (Big Idea #3) on Thursday.
The means of interpreting an isotopic charge was then studied. This idea will take some more time, and we will revisit it on Thursday, as well.
Students were asked to complete the defintions for the terms found under Goal #1 for this unit. It would be quite helpful should everyone complete that work.
We moved through and completed the notes/readings on page 42.
Thursday 3 March: This evening's lecture tried to build upon our work regarding the electromagnetic spectrum.
The class members were asked to focus upon the common threads woven through the electromagnetic spectrum.
We reviewed some of the basic properties from the other night. Those common threads include;
1) The wave of any energy on the EMS is more or less a sinusoidal wave (as opposed to a sound wave which is described as a longitudinal wave)
2) Each wave can be described with the terms; wavelength and frequency. The greater the wavelength the smaller the frequency and conversely, the smaller the wavelength the greater the frequency.
3) Each of the types of electromagnetic energy travel at the speed of light. We discussed the concept of a light year being a distance (not a unit of time). We discussed that as we gaze at the stars, we are witnessing a long past history, as it has taken centuries for some of that light to reach us here on Earth.
We discussed television and radio signals from the 1950s which are now leaving our solar system. We took a quick look at the Very Large Array (VLA) and its purpose.
The above were mentioned on Monday, but reviewed and developed a bit more during Thursday's lecture.
The big take home message from Thursday however, was another common thread - and a very important one at that. It did not so much describe the wave but rather spoke to the origin of the energy.
That origin is found in the movement of electrons from high(er) energy levels to low(er) energy levels in an atom.
The type of electromagentic energy released by the electron(s) of an atom depends upon the change in energy an electron undergoes as it moves from a greater to lesser energy state.
Per the Law of the Conservation of Matter and Energy, the change in potential energy of an electron can not just disappear - but it can be converted into a form of kinetic energy - such as electromagnetic spectrum energy.
This is very important to recognize, as it links infrared energy to light energy to radio waves. The source of these energy waves is the same ....the movement of electrons and the conversion of lost potential energy to another form.
We then focused attention upon the Subtractive Theory of Color, in an attempt to bring in an everyday application to what we encounter. We can also look at the color of the sky and water, in terms of the absorption of certain wavelengths of the electromagnetic spectrum and the reflection of others. We see the colors reflected.
We took some time to look at "why plants are often green" and why leaves change color in the Autumn. We looked at the hypothesis that the anthocyanins (reds/purples) are most likely a protective measure limiting damage to the leaf due to continued exposure to sun, in the absence of chlorophyll. This is one reason why you might find a leaf with a reddish surface (facing the sun) while the underside of the leaf is more yellow/orange.
The take home exam was handed out. It is due Thursday 10 March 2022, in class.
Summary for 24 and 28 February: On Thursday, a new note packet was given out, as we are just about done with the current one. So, be sure to grab a copy during the next class, if you were absent.
On Thursday 24 February, students were asked to create their own summary of the class, for bonus points. Thus, I delayed the publication of a summary of that night. Now, I have included a summary below.
We are just about done with energy. This work has focused upon three ideas;
1) potential energy as chemical energy
2) the conversion of potential energy to kinetic energy
3) the expression of kinetic energy in terms of the electromagentic spectrum
Some of the "everyday applications" used to help bring relavance to these ideas are;
1) the connection of changes in / conversion of potential energy and climate change, using infrared active molecules such as carbon dioxide and water.
2) the relationship between the various forms of electromagnetic energy and the changes in potential energy of electrons; such as "heat", ultraviolet tanning, visible light and microwaves.
Thursday 24 February, saw the lecture focus upon in visuals from a video clip demonstrating rotational, translational and vibratory motions associated with molecules. The clip can be found in your notes, on page 31.
We focused upon the vibratory (vibrational) motions of bond stretching and bending. Bond stretching takes on a very special position as we blended climate change, energy conversion and potential energy.
In terms of our work on climated change, we saw that infrared molecules such as carbon dioxide can absorb energy and undergo bond stretching (but no breakage) . Bond stretching represents an increase in potential energy. As the bonds return from a stretched configuration to a less stretched configuration, the potential energy decreases, and is often converted into some form of infrared energy, radiating back into the atmosphere of Earth.
This is a terrific example as to the convergence of big idea #1 (The Law of the Conservation of Matter and Energy) and big idea #2 (Potential Energy).
The lecture on Monday, 28 February, picked up on this conversation and expanded it to a more detailed investigation of the electromagnetic spectrum (EMS).
The EMS is associated with transitions in energy (higher to lower) of the electrons of a chemical species.
As electrons transition from higher levels of energy to lower energy levels, the difference in energy states is converted into some form of electromagnetic spectral energy, such as visible light, microwaves, radio waves, ultraviolet waves, x-rays, and infrared energy.
We spent some time explaining the relationship between the wavelenght of a wave. For instance we discussed how x-rays can cause damage to tissue, because the size of the wave and the size of covalent bonds can "match up". We then took a look at a video of "Galloping Gurdy" (click for link), and used this event as a metaphor for what may happen with matching frequencies of energy.... such as bonds and EMS.
We also did some group work focused upon the movement of energy from high(er) to low(er) levels. This understanding helps to refine the conception of such ideas as a draft in a house. Importantly, this idea can also help realign and/or reinforce one's understanding that we are the "hottest thing in the environment". Hence a bag of ice put to a swelling ankle, is heated up by our body, as the energy moves from high to low. There is no such thing as "cold energy".
We investigated what we mean by temperature (average kinetic energy), how a thermometer works and the definition of radiation. Not all radiation is nuclear radiation ... remember that!
Students were asked to use the link found at the bottom of page 36 to review the video which explains why plants are green.
Thursday 17 February: The work centered around energy. One idea was central and it was accompanied by a smaller issue. The central idea was about potential energy and the smaller issue dealt with the conversion of potential energy to kinetic energy (primarily in the form of thermal/infrared energy ... what most folks somewhat erroneously call, heat)
With Thursday's lecture, we essentially have covered Big Ideas 1 and 2. A big idea is one of those overarching pieces of theory we can use over and over again to explain chemical phenomena.
Big idea 1 is the Law of the Conservation of Matter and Energy. I mean, let's face it...I haven't shut up about it.
Well Big Idea 2 , from my point of view, is all about Potential Energy.
Potential energy strikes at the very heart of our study of chemistry. Those covalent bonds introduced in the Covid work, are chemical energy and that is a form of potential energy. And bonding is so important when we start talking chemistry.
Per our notes potential energy is all about the distance or postion between objects relative to some assumed standard.
This led to any number of metaphors and examples.
In terms of chemistry I tried to develop an understanding that the conversation must be linked to the law of the conservation of matter and energy. As potential energy decreases, that energy must "go somewhere" and very often it is converted into a form of kinetic energy, such as heat.
And, for this part of the idea of potential energy we really worked at understanding the physical aspect of molecules moving away or closer to each other.
We then moved to understanding the valence electrons as those with the greater amount of potential energy relative to inner electrons.
Finally, we moved to making bonds and breaking bonds. To make a bond, species must decrease their potential energy. To break a bond, the potential energy must be increased. Remember I used the model of a pen and pen cap to help with that idea.
Anyway - we started first with the physical ascpects - such as phase changes and how they apply to our life. So here we ago in this review ....
Gaseous water vapor has a greater potential energy than liquid water. Hence as gaseous water vapor (like that which can be produced during a hot shower), heats the surrounding air as it condenses into liquid water on a mirror.
There is a "positional energy" between the molecules of water in the gas phase. As the water vapor condenses, the molecules of water come closer together. Their position relative to each other, decreases. This decrease signifies a decrease in potential energy. That energy must go somewhere and by drawing upon our grasp of the law of the conservation of matter and energy (in that energy can be transferred and/or converted to other forms), that decrease in potential energy is converted into some sort of kinetic energy. We will see this connect more specifically as we study the electromagnetic spectrum.
But some were skeptical with a warming bathroom as the shower ran - because when we get out, often we are cold. Well that is another aspect of potential energy , very much akin to sweating.
We must remember that we are the hottest thing in the room, more often than not. With water on our skin (whether due to a shower or perspiration), our body is like a stove. The energy of our body is used to heat up the water and increase that water's potential energy. As the potential energy of the water is increased by the energy of our body, the water molecules drift farther from each other .... You see, that heat energy coming from us is converted to potential energy. The outcome is that the water is evaporated into the atmosphere as a gas, and the increased (potential) energy experienced by the water, comes from us! Thus this is a cooling process... as we lose energy to the water.
This was made clearer with the less-than-optimal example of falling into cold water. Our body immediately tries to heat all that water up! Energy moves from higher levels to lower levels and we are the hottest thing around!
Water on our skin is not absorbed, rather the energy of our body is used to evaporate that water away, via our superior (heat or infrared energy) being converted to potential energy of the water.
This is one reason why if the atmospheric temperature is SUPERIOR to our body temperature, we cannot cool down. We are, in this case, not the hottest thing around. If we continue to work out or play a sport in such an environment, our body stuggles to maintain a reasonable, steady, internal temperature. This is a time for worry.
Once we wrapped up this type of work regarding phase changes, we moved onto the "bow and arrow" demo (calm down if you weren't there ....ask someone) . From this we could begin to develop an understanding that the outer electrons of an atom had greater energy than the inner electrons, as a rule.
Then we spoke a little about bonding.
The class wrapped up by students answering three questions:
What was the central idea tonight?
What did you learn about that central idea?
What example or applications apply to that central idea?
The cental idea seemed to include:
- energy is the ability to create a change (or to do work)
- when discussing potential energy we compare things to an assumed relative position.
Learning included:
- changes in energy may be associated with a change in position….
- energy is lost / decreases when you form a bond and it increase when you break a bond (bond making = exothermic, while bond breaking is endothermic)
Examples/ Applications included:
- a punch, a bat swing, a racket stroke .... in that there is more energy if you complete the motion
- the greater the distance the greater the energy, like with a bow and arrow
- sweating is a cooling process.
- valence electrons are the greater in energy than inner electrons
- valence have a larger potential energy as they are farthest from nucleus
- a roch at top of hill has greater potential energy relative to the rock on the ground
- we are hotter than the water on us and our energy is used to evaporate that water, by increasing the potiental energy of the water.
Not a bad evening's work my friends! Nicely done!
I will see you all next Thursday. There is no lab on Thursday, as there was no lab on Monday!
Monday 14 February: Sorry for the slow update - but I am back online! Monday night wrapped up the first part of Unit 1. Within the context of matter and energy , we have been covering quite a bit of material. We ended at page 28 - the last page of the first set of notes.
Monday's lecture focused upon the end pieces of what we term as, mixtures. It then covered means of identifying an exothermic or endothermic change as well as chemical reactions.
In terms of wrapping up mixtures, we took a look at hard water. The term, hard water, is often applied to samples of water with higher concentrations of Ca+2 ion and Mg+2 ion. These ions interfer with suds formation of soaps and shampoos. They form precipitates which can form deposits on pipes and soap scum in the sink and bathtub. We also touched upon "soft water".... or rather water so lacking in the above ions that rinsing soap off of ourselves can prove to be difficult.
Exothermic changes are those in which the activity of the chemicals in question releases more energy into the environment of the chemicals (the surrounding air or water, if in a beaker). There is a net release of energy.
On paper, the energy signature (kJ) of an exothermic change will be on the product side of a reaction equation.
The classic example is a fire. More energy is generated (released) by a fire than is absorbed when starting a fire. The energy of a match is utterly overwhelmed by the energy released as a fire continues on its own, after activation.
While fire is the classic example, a common sort of exothermic change is a cooling process. What may confuse students is that freezing or condensation must be classified as exothermic.
Huh? Freezing is not like a fire! That appears to be a bit counterintuitive - yet, if you look at the definition, in which energy must be released by the chemicals in question to the environment, it can make a good deal of sense.
Cooling is exothermic. What must be true about any cooling process? ... Yep, the overall termperature must decrease. Energy MUST LEAVE THE CHEMICALS and move to the environment. (Energy moves from areas of high concentration to lower concentration.)
Hence, in a cooling process, such as freezing water to ice, energy must exit the water system and must, therefore move to the surrounding environment. Hence, freezing is exothermic!
The converse (as in the opposite of) to an exothermic change is an endothermic change. This refers to a system in which the chemicals in question absorb more energy than is released. Heating up water from 15C to 75C is and endothermic process. Much more energy is being absorbed by the water, as it heats, than is released.
With these energy exchange issues completed we moved on to a study of chemical reactions.
There are two skills I hoped to have developed.
1) I wanted class members to be able to identify a chemical reaction when they were given a test.
2) I also wanted class members to be able to identify a chemical reaction in their life.
The skills are a bit different. The first is the easiest. A chemical reaction will have new bonds produced. On a test, we can see this as a rearrangement of the element symbols. The notes have multiple examples.
The second addresses my desire for this class to be truely about "everyday chemistry". To identify a chemical reaction in "real life" you may wish to consider finding 2 or 3 of the following visual clues.
a) the production of a new solid
b) the production of a new gas, which results in a release of bubbles
c) the production of a new liquid (tough)
d) a bold change in color
e) an energy change (the release of energy or the absorption of energy).
For instance, it is reasonable to classify a wood fire as a chemical reaction. New solids (ash) are produced. New gases can be smelled as wood combusts. Clearly there is an energy change.
Rusting of iron is also a reasonable example. Iron turns to iron oxide (a different, more brittle, flakier solid). There is a change in color, as iron oxide (rust) tends to be anywhere in color, from yellow, to black, to reddish brown.
Okay, be sure to have the problems up through page 28 completed. Write with questions and/or bring in your questions to class.
Thursday 10 February: Last evening's lecture was all about mixtures. I thought we would get into energy but, these things happen. There was the main idea regarding mixtures but there was also, a smaller yet important sub-theme which dealt with the strength of a chemical bond, like the one found between the atoms of hydrogen and oxygen in a water molecule.
We reviewed that the elements which comprise a compound tend to have different properties from the compound they make.
However, a mixture tends to exhibit the independent properties of the components used to make the mixture. For instance, if you were to add sweetened ice tea mix to a glass of water - no chemical reaction occurs. Rather you just make a mixture.
Using the word "dissolve" is a good clue that you have a mixture.
Other clues that you are dealing with a mixture include:
- a list of ingredients, a very common or nonspecific name (eg: shampoo, toothpaste, gasoline, spice, air, vinegar etc...)
- a grade such as 87 octane, 2% milk, 2% salicylic acid, 9% hydrogen peroxide
- a heterogeneous sample of matter
Okay, back to sweetened ice tea ... The sugar in that mix, is still sweet tasting. The water is still a fluid, the color is consistent. The individual properties of the components of a mixture don't really change all that much.
We spoke about the Earth's atmosphere's composition and the content of our inhaled and exhaled breath. Yes, we do breath out a fair amount of oxygen .
We took a quick look at the use of oil in our society. Yep, we are absolutely bathed in the stuff, as it were. We need oil for any number of molecules used to make a host of products. One of the challenges for the future is conserving oil for our production means and balancing this with the combustion of fossil fuels (which we now know.... are not from "rocks" or fossils, in the strictest sense of the term).
We also looked at the work of Alice Ball, using the SciShow video found
at: https://www.youtube.com/watch?reload=9&v=dymJcBkGlbs&feature=youtu.be
Her work was absolutely critical in developing an effective treatment for leprosy, prior to the development of antibiotics. Her techniques also shadow our own lab work in that we will perform a saponification as well as an esterification! Remember, we are all about making connections between our work and the "everyday world".
Thus, jumping off of Ms. Ball's amazing work, we can again see that mixtures can be separated via a number of means, some use chemical reactions while others use physical means such as filtration, boiling, chromatography etc...
This last thread led to a detailed discussion of our sub-theme regarding the strength of a chemical bond. We used the idea of boiling water from liquid to its gas phase. Using the diagram at the top of page 24,
I tried to emphasize the energy requirements to break a bond. The energy required to separate a mixture is often much lower.
So, think about boiling water. Do you realize that we simply move the molecules of water so far away from each other, with the energy added to the sample of water, that we form the liquid into a gas? There is just a change in phase or state of matter.
We DO NOT break the bonds between H-O and produce H2 and O2. Hear that again: We DO NOT produce hydrogen gas and oxygen gas when we boil water. We can infer this because there are no explosions. We know that hydrogen gas burns and oxygen supports that combustion (recall the Hindenberg).
Forming these gases DOES NOT occur when we boil water. Thus the conclusion is that what is produced is water vapor. The molecules are intact, the bonds are not broken.
Now imagine how much energy is in that boiling water! That amount of energy is INSUFFICIENT to break the chemical bond between H and O! Yet, chemical reactions which do have bonds breaking and making occur in our bodies every second of our lives. This is really amazing! How does this all happen? Well, those are topics for future lectures.
Students were asked to grab a few notes on pages 25 and 26 using the online services. Additionally folks with well water may wish to bring in a sample of that water for testing next week. Be sure your lab is read.
Write with questions.
Monday 7 February: Tonight's work was pretty straight forward. The terms; substance, element, compound, mixture, homogeneous and heterogeneous, were introduced formally. We ended the evening on page 24 of the notes.
This week's lab, chromatography, is all about the separation of a mixture, so lecture and lab are still meshing.
Okay, so here is a brief review...
There are essentially 2 overarching terms for us to use, when trying to classify a sample of matter. We can use the term Substance or the term, Mixture (but we cannot use BOTH terms as an adjective of a single sample of matter.)
For our work, we shall describe a sample either as a substance or as a mixture. Thus a sample is either a (single) substance or a physical merging of multiple substances (called a mixture).
All substances are homogeneous (uniform in composition). We can "picture" this definition by asking ourselves; "How many different types of matter do we see"? When the answer is "I see one type of matter (that is it all looks the same) ..." then we can say the matter is homogeneous.
When we see multiple different types of matter... e.g. a piece of granite, then we can describe the sample as heterogeneous. Substances must be homogeneous and mixtures may be either homogeneous or heterogeneous.
A reasonable means to think of these terms is that the terms do not imply how many types of matter there actually are - but rather, how many we "see".
Subtances my be further classifed as elements or compounds (but not both).
A sample of matter, may be an element (species which each have the same atomic number) or a sample of matter my be a compound (chemically bonded species of two or more different elements in a definite proportion). The term definite proportion lead to a discussion on subscripts. In this discussion we worked with water H2O and H2O2 (hydrogen peroxide). In water, the proportion of hydrogen to water is 2:1 in terms of atoms. In the compound hydrogen peroxide the proportion is 1:1 in terms of species.
In terms of mass the relationship of hydrogen to oxygen is 2 : 16 or 1: 8 (Don't worry how I figured that out , I am just trying to drive home a point)
For hydrogen peroxide, the relationship of hydrogen to oxygen , by mass is 2:32 or 1:16.
You see, compounds have definite proportions ...change the proportions (if possible) and you change the compound.
And then someone asked about H2 + O2 --> H2O inwhich a flammable gas, and a gas which supports combustion (burning) chemically combine to produce an utterly different product (which actually puts out many fires)
This is key about compounds. The properties of the compound may be very different from the properties of the elements which make the compound! This is not really accurate of mixtures.
Mixtures may be of varying proportions. (You might add 3 teaspoons of ice tea mix to a glass of water, or you might add only two. This is what I mean by varying proportions.) The Earth's atmosphere is a mixture of gases and fine particulate matter. Over the millenia, the percentage of oxygen has changed from upwards of 26% to 21% ....(again, a varying proportion).
You may have a small amount of salt in water (as in a estuary like the mouth of the Hudson River, where fresh river water mixes with oceanic salt water) or a much greater amount of salt in water, like the Pacific Ocean. Mixtures have variable proportions to their compositions. Or keeping with this theme, the salinity (salt content) of the Atlantic Ocean is greater than the salinity of the Pacific Ocean! You see? Even ocean waters (mixtures) can vary in their composition.
This is key about mixtures. The components of the mixture tend to maintain their individual properties! This is one of the reasons why we can separate those components using relatively simple physical methods.
Thursday will see us focus upon mixtures, (with a look at an early treatment for leprosy and a look at a barrel of oil) and then possibly move on into energy.
Take a look at the notes...write with questions.
Thursday 3 February: We are up to page 21 of the notes. We are beginning to make some headway.
Last night's lecture material centered on density as a state of compactedness of the atoms/molecules of a material. We spent some time getting comfortable with what sinks and what floats (or rises) given differences in densities. The small problem set on page 17 was important.
Once comfortable we could move on into a number of threads.
First, we worked at trying to understand why lakes / ponds freeze at the top and not the bottom. It's a good thing that they do freeze at the top because ice forming anywhere else would more than likely kill any of the vertebrate and plant life in the water!
The key is that water is really different from almost all of the other materials of which we know. You see, as most materials freeze, they become denser ... more compact.
The above is NOT true for water! Water is densest at 4C (about 1.00 g/mL), but it freezes at 0C. The natural conclusion is that 4C water is more compacted than 0C ice-water and so we could conclude that 4C water would sink through any other water, regardless of that other water's temperature.
The top layer of water is in contact with air. Let's assume that air is colder than the water. Energy will flow from the water to the air and the water will cool. As that water approaches 4C, it will sink down into the lake.
As it sinks a new layer of "surface water" is revealed and it too will cool to 4C and sink. This cycle of replacing the top layer of water, by allowing it to cool and sink, only to be replaced by a another layer of water goes on until the whole of the lake water is at 4C. (Read that again.....)
The surface water will continue to cool below 4C (assuming the air temperature is much lower). At this point that surface water (which is lower than 4 C) will be automatically LESS dense than all the water beneath it. It does NOT sink. Rather, this surface layer continues to lose energy to the air and ultimately reaches 0C (or colder) and it freezes. Ice, with its density of approximately 0.99 g/cm3 will "float" .
Now, the second thread to the conversation evolved from the actual structure of ice vs. water. As ice forms (recall water is weird), the volume expands and thus for a given mass, the density must decrease. (analyze D = M/V ... As V increases, at constant M, then D must decrease)
The question is WHY does water do this?
I took some time to discuss the distribution of partial charges across a water molecule. The oxygen of water is slightly negative and the hydrogen are partially positive. We did not discuss why...just the "is".
This means that the partially positive hydrogen of one molecule will be attracted to the slightly negative oxygen of a SECOND (different) molecule of water. There is a diagram on page 19.
(Here's where we veered off the topic of density): These partial charges exist on a lot of matter. Matter, like the blown layer in our face masks. This mid-layer of a well made face mask like an N95 or KN95 or good surgical mask has lots of charges.
Viral particles also have partial charges and the mid layer of masks traps viral particles preventing them from passing through into our respiratory system! (recall: opposite charges attract!)
We then discussed to a small degree how the virus works, and how the vaccines work to protect us.
We then wrapped it all up , and took some "wrap up" or closing notes on page 21!
And here is the big Take Home Message:
You see, the chemistry of one system can be used to help us understand the chemistry of a completely different system - because chemistry is chemistry. You may / may not be fascinated with why water-ice expands as it freezes. However, there are threads here that help us build our science (knowledge). It is how we apply these fundemental ideas that makes things different - but the chemistry is the same. Think about that.
Write with questions.
Monday 31 January: There were two ideas to grab onto in this class. The first focus was on the idea of pressure.
1) We are measuring pressure as the force exerted on the sides of a container of gas. For our work, the measurement of pressure is greatly affected by the number of interactions a gas molecule has with the sides of the container. This value is greatly affected by temperature. A hotter gas has a greater acceleration, which affects the pressure as seen in the equation P=(mass)(acceleration)/area.
2) Using our diagrams of a trapped gas trapped in a cylinder with a moveable piston we deduced that as pressure on the gas was increased, volume of the gas was decreased. We can infer that pressure was increased because the gas molecules occupy a smaller volume and interact with the sides of the container more often. Thus, we wrote down as ancillary notes, that as Volume (of a trapped gas) DECREASES, pressure exerted by that gas INCREASES.
3) The inverse is also correct: As the volume of a trapped gas is allowed to increase, pressure decreases (we must assume a constant temperature). For those from prior chemistry experience this is Boyle's Law, which expresses this inverse relationship between pressure and volume, at constant temperature.
4) But for us, we could then apply this idea (as volume decreases, pressure increases) to how we as mammals breathe! Remember, this is Everyday Chemistry, and we focus upon such applications. So check out page 13 of the notes. Only the internal pulmonary pressure changes due to compression and/or expansion of trapped gases, as the diaphragm and rib cage move.
5) We also applied the idea of pressure and the amount of gas to the atmosphere. We introduced the unit of atmospheres (or kilopascals) to associate with pressure. We used the diagram found on page 11
The second idea was working with the idea of extensive and intensive properties of matter.
Constants at a known temperature and pressure, such as melting point and density are intensive properties. We can use these intensive properties to help identify substances. (We wrote this down).
Variables such as the amount of mass, volume or length , which can be changed by simply adding "more stuff" are extensive properties.
I used the analogy (and analogies are limited, so don't be too literal), of a price for 1 tee shirt vs. the entire bill you pay when purchasing a bunch of tee shirts. The price per 1 tee shirt is like an intensive property. It is a constant per 1 shirt. The total bill changes depending upon HOW MUCH you purchase. If you buy 5 shirts or 10 shirts, the total cost changes. Thus the total cost is like an extensive property.
We kept going back to the example of an iceberg vs. an ice cube (page 14). This is an important example in terms of helping students to latch onto the ideas of extensive vs. intensive properties.
Practice problems on page 15 were assigned. (You can get the answers using this website and opening the online version of the notes (Unit 1 Part 1). Select the area near an * and change the font color.)
We then touched upon density, but we will finish that discussion on Thursday. Don't forget, A Capsule of Covid Chemistry is due on Thursday!
Write with questions!
Thursday 27 January: There are a few things to cover:
1) A new assignment was given out... A Capsule of Covid Chemistry. A link to the assignment may be found on the Guided Notes page. Hard copies are due on Thursday, 3 February. Write me with questions.
2) We are on page 10 of the note packet and student are asked to complete page 10, using the online notes. That will wrap up our work on pressure. A student asked a stellar question about what happens to a gas when put under high pressure. I altered the question just a bit by adding what might happen under extreme pressure accompanied by a drop in temperature? This led us to our first conversation about changes in phase. Then when one student raised the issue of putting a gas under high pressure without a drop in temperature, as in a car cylinder , we could talk about autoignition when mixtures containing octane are compressed! Not a bad 15 minutes there people. I was so pleased. People were engaged, risking, and asking darn fine questions, as they pursued their interests. Good on you!
3) The demo on volume went off without a hitch ... always good to see. The take home message is that liquids (like water) have a constant volume, but not a constant shape. The song, btw, was a variation of Twinkle Twinkle Little Star by W.A. Mozart.
4) We spent a fair amount of time discussing gravity . Don't forget about our 120 lbs astronaut on Earth compared to her 20 lbs on the Moon. We did a little warped space = gravity work, using a trampoline as an example. I gladly admit that I warp the fabric of space less than the planet Earth. We tossed ideas about Superman around a little bit, and no, I cannot explain the laser beams out of his eyes ...but I could reasonably stretch an explanation to flying. Toss in the possibility of a little speciation if Mars colonies become a reality . Hmm, ad hoc and stir!
5) The term weight is of value only when discussing a mass in different gravitational fields. Weight changes as gravity changes, but mass does NOT change. Our weight would change slightly were we at the Earth's equator, at the top of Mt. Everest, or Death Valley.
6) It is reasonable to suggest that Pluto is not a planet. We could infer this by comparing the weight of a student on Earth, compared to their weight on the Moon and then on Pluto. We may infer from the data derived due to the celestial bodies differing gravity, that Pluto is significantly smaller than our moon. That caused on student to ask why the moon is not a planet . Yet another nice question!
Okay, so there is a new assignment. Lab reports are due next Monday and next Thursday. Be sure to follow the Lab Report Template found in the Introductory Packet. Be sure to cite your research. If you needed to look it up, you need to cite it. Write with questions.
Monday 24 January: No big assignments were given out. I simply want to update what we have done and where we are in the notes, for students who have just dropped in and for those students who have been out. We have been working our way through the basics of vocabulary, with matter, energy, mass, volume and weight. A fair amount of time has been spent on differentiating between matter and energy ... how to tell one from the other and the rationale behind those reasons. Expect to see questions regarding the Law of the Conservation of Matter, Energy and Charge on an exam (For example: You want to be able to deal with the definition as well as a question such as #2 on page 7 of the notes) .
We worked away at the definition of mass- which under the best of circumstances is a tough one. We reached page 8 of the notes. Thursday will see us wrap up an understanding of weight and volume... Then we really hit the road!
Monday night had their first lab. The Thursday night crew will get the same lab. We also went over the locations of the exits from the lab and safety equipment: fire extinguisher, chemical shower, fire blanket, and the eye wash.
Thursday 20 January: Have the introductory packet read/reviewed in preparation of the first lecture. A hard copy will be provided in class. Be sure to spend a good amount of time reviewing the laboratory safety measures found on page 11. Be ready to ask any questions of clarification.
For your lab on either Monday (24 January) or Thursday (27 January) be sure to have the lab ALCHEMY read and prepared. Be familiar with the experiment per the introduction of the lab. Read over and familiarize yourself with the procedure and the questions.