The biggest lesson I have learned is that my students need to practice. 3 or 4 problems is not enough. They might whine somewhat about the worksheet, but they are hopeless without a lot of practice. The thing to do is not to have other activities replace practice, but to have a lot of practice incorporated into more authentic activities (e.g. labs).

Practice, practice, practice.

And slow down.

and don’t assume anything, especially if you didn’t teach them last term.

Today was a bad day in everything but my teaching. We are starting “shape.” This is how I think of Lewis structure/VSEPR stuff. We are taking steps towards thinking in three dimensions, which is one of the wonderful things about chemistry.

I managed to start at the beginning. I reviewed their prior knowledge of valence electrons. I then defined Lewis structures. Then I did the LS for the elements whose valence electrons they had just found for their POD. Then I started with two simple molecules (methane and ammonia) and demonstrated “easy” ones. Then I outlined a method for figuring out the number of bonds and the number of non-bonding electrons. Throughout this I would show them 2, and then they would do one. Tomorrow we will start of with practice (I modified a worksheet from another teacher’s website). Then I will show them some examples with multiple bonds and define resonance. Then we will practice more.

Baby steps. Lots of practice. Despite it being a fairly teacher led day, the students seemed quite positive. I think I actually taught something properly, instead of jumping in all willy-nilly with only enthusiasm and assumptions.

One of my students referred to a task we were doing in class today as “touchy feel-y flower child” methods. Not something that one expects to hear in chemistry class, when classifying compounds as either ionic, polar covalent, or non-polar covalent.

This was because I was discouraging the method in the book, which no one except high school textbook authors uses. High school books always want you to subtract the electronegativities, and compare the difference to some arbitrary standard that changes from book to book, to classify a compound as ionic or covalent, polar or non-polar. So annoying. What I always did, and say real scientists doing, was using a general sense of periodic trends to compare polarities, electronegativities, and electron rich and electron poor areas. The textbook method is too formal and impractical, it is not useful. I guess my use of the word “intuition” or “feel” for the periodic table was frustrating for her; she describes herself as having a very “math” brain. I think it is fair to say that most scientists think mathematically =). But sometimes being overly quantitative is arbitrary, time consuming, and provides no useful information.

They were not convinced. A very interesting and unexpected dilemma.

I have been expanding on my environmental chemistry unit idea. The only problem is that I am not sure if six weeks is enough time. That is what I have between Spring Break and the end of the year. It would encompass just about everything we will do. Electrochemistry, Acid/Base chemistry, concentration, ions and metals, potentially organic (I’m not sure about tests for organic pollutants) and we could at least discuss radioactivity in connection with pollution even though that is not a problem here.

The final lab/project (possibly test) would be to write a procedure and run a series of tests on the river water over the course of two class periods. They would have to do a write up and presentation on their test results, and on possible problems from the pollution or clean-up ideas. (clean up ideas have more potential for chemical explanations).

To prepare them to do this, they would need to do at least four preparatory labs to learn the lab techniques and theory so they could write the procedure. They would need to have at least one, preferably two previous lab write-ups so they knew how to do those (they are not really part of the curriculum here for some reason). They would also need to learn about environmental chemistry in a more general way.

The coolest idea I have is that they can do a lab where they make solutions of known concentration and measure their absorbance, and then when they get the data from the river they will be able to figure out the concentration from the class graph of concentration vs. absorbance. (each pair would do a different concentration so that we could have 10 or so points on our graph).

Can I plan this fast enough, so that I can start them on it????? Is this actually possible or is it way over my head?

Part of me thinks this easier to plan, because I have this big goal that everything needs to lead up to. Every concept we learn, every equation we practice, will somehow need to help them be able to do this final task.

I am less worried about my students content knowledge than about their lab/problem solving and general independence. Can I teach them how to be that independent in six weeks? That is a lot harder than just teaching them the chemistry.

Looking for labs, I found some great ones on water quality. (I should of thought of this myself, they do a huge unit on this in FOS 1)

Edited to add: Here is the link with the lab that inspired me.

Potentially encompasses acidity, metal ions in solution, redox, organic, absorbance (turbidity), and the environment.

I am “fortunate” enough to live near a rather polluted water source, so this could be very interesting. Practical. Not that they care about how yucky their water is, but it has to be better than me lecturing.

Tuesday a college group came to do Romeo and Juliet for the Freshman and the magnet students. It was first and second periods (and part of homeroom). Many of my students are in the magnet program, so many of my students were gone. I had no idea what to do. I could present something new, and then have 12 kids in two different classes to re-teach it to. So I did something I thought would be review.

They were struggling with the dissolution of polar and ionic molecules. I made them a worksheet with more practice. I thought, well, we’ll do it in class. They can work in partners and then put the answers on the board. It will be a little easy and boring (especially for third period).

That was not the case. I’m really glad we did that. My students said it was helpful, and most of them were quite confused about it. We spent a lot of time reviewing how to identify ionic and polar compounds. I did not spend that long on this last week, because they had learned it already. Or, I should say, they had been taught it already. I think that most of my students are now starting to get it.

We talked about hydrogen, which is sometimes a metal, in the same way that ‘y’ is sometimes a vowel.

Most of them said they understand it better, but only one or two students said that they now get it. I don’t know what to do, spend another day on it. Polar and ionic are two central concepts in chemistry, and they are powerful for explaining things. I’ll have to think of some way of reviewing the material before the test, but we need to get to acids and bases. (If I sound like I’m in a hurry, it’s because I want all of 4th quarter for organic/biochemistry).

I assumed that my magnet students (many of whom are quite good students) would be fine without yesterday, but that is not the case. So I still have to re-teach 25% of my students. Sigh. I just wish they would have assemblies some other period.

Today I learned first hand how much time it takes for students to really think about open-ended questions. I had alloted 10-15 minutes to let them get an answer to my question, and it took over 30 for all the classes.

The focus question for the day was: How can we tell how much solute is in a solution?  I had them brainstorm the ways solutions are around us every day (Kool-aid was a very popular example), defined a few words (concentration, dilute, saturated), and talked about how we measure the solute and the solvent (volume, mass, counting), and then asked them to answer the focus question. As the day went on, I got better at presenting this question in a way that made sense. I told them that we needed a quantitative expression that we could use to label a solution, so that when we only needed part of the solution, we could figure out how much solute was in it. I used the example of having a party, and having a gallon of iced tea with 2 cups of sugar in it. I asked them how they could figure out how much sugar is in each cup of iced tea.

The strategies most students used involved making up a problem similar to the example, and solving it, and then trying to generalize from their equation. Most students came up with percent volume as a way of defining concentration. This is quite logical because most of them were thinking about food and cooking, and in America we cook by volume. The next most popular was grams solute/liters solvent, and grams solute/grams solvent (practically molality). One or two groups came up with moles solute/liters solvent.

This was one of the most open-ended things I have asked them to do. I did not let them use their books. I was pleasantly impressed at how well the pairs (we did HOFBrINCl partners) debated and problem solved together. A lot of the pairs spontaneously formed foursomes, and that was fine with me. Most of the groups were thinking algebraically, they were starting to convert their intuition into mathematical expressions, with more or less guidance from me. It was pretty exciting to see.

When they would ask me if their idea was right, I told them to make up a sample problem and see if they could solve it with their expression. I wrote down all the ideas each group came up with, and next week I will show them all to the classes.

I am torn about which way to go next. The reason I am torn is that this technique is big on problem solving and thinking skills, but low on content priority. Molarity is an important tool, but it is not a central concept. Ideally I would spend large amounts of time on questions that are high priority for both. The fast way is to circle the expressions that are molarity and molality, and explain that these are what scientists use, and start with the math. That is basically giving them the right answer. Or, I can commend them on finding an expression that works so well for catering, and give them a simple stoichiometry problem to solve and ask them figure out which units they would use, setting them up to find out molarity on their own. This would take longer, but it is more completely inquiry centered and student led.

All the students got that what is needed is a proportion between the amount of solute and the amount of solvent or solution. They just did not use the most useful units. They do not naturally think in terms of moles. Hopefully that is enough to build on to see the logic of molarity and make it easier to use. I think most of them also experienced how scientists sometimes sit around and make up something that makes sense, and then it becomes standard.

The outline: Combustion Demo, Chemistry of Attraction, Evaporation.

I still needed a demo or a lab this week, and although I didn’t have any good ideas for something solution related, I thought that Valentine’s Day was a good excuse to do a demo involving candy. I did a simple combustion reaction, where you decompose KClO3 with heat, and then add any thing with sugar or starch. There is a good description here. I used the conversation hearts, and then I did a pencil (the graphite gets left behind). The combustion is a very bright, light purply-pink, and it makes a cool sputtering sound, a lot of smoke, and the smell of burnt marshmallow. I originally saw this done with a gummy bear.

I did not link it to my curriculum. This was shameless pandering to my students with bangs and flashes. That is one of the reasons I became a chemistry teacher.

For the chemistry of attraction, I talked about phermones, the sense of smell, and attraction in human relationships. This was an attempt to get relevant. I figured sexual attraction is always interesting to people. It is a little off topic, but interesting. I wanted to have an article for them to read, instead of having me summarize the topic, but all the articles I found were either really lame and unscientific, or really technical and difficult for high school readers. In the end, I brought it around to phase changes by talking about sweat evaporating (this is how the phermones get from our skin into someone’s nose). We then talked about  how evaporation cools things down, which is one of my content goals for the solutions unit.

I also offered them all some candy conversation hearts. I had a big bag.

Overall it was an engaging day for them. I could tell they were interested in the ideas presented, and the attraction thing did make evaporation more interesting to them. The biggest problem was that it was all very teacher led. Something to improve for next year.

We did another chalk talk today. It was less successful. The task was to compare and contrast ionic and molecular bonds. They had done this for homework, taking notes from their book as they read. I think it was less successful because it was less open-ended;there was more a sense of needing to have a correct answer to put up there.

After the chalk talk, I clarified, we reviewed electronegativity, I gave them examples of polar bonds, we reviewed salts (and how they are always ionic), and we diagrammed a salt (KOH) and a polar molecule (NH3) dissolved in water. The KOH was on their homework.

A hint to remember for next year–Hydroxides are confusing examples of salts, because of their OH bond. When you tell students to memorize OH, NH, OC, and NC as important polar bonds, and then give them a salt with an hydroxide ion, they get confused. It is too many concepts to deal with at once. Save the hydroxide ions for when they are good at polar/ionic classification, and after salts and hydroxide ions have been reviewed.

I made up more practice problems having them diagram the dissolution of ionic and polar compounds.

I just realized today that I forgot to emphasize “like dissolves like.” I consider that fairly central to the concept of dissolution. I will have to figure out a way to bring that in.

Interesting story about isotopic ratios being used in drug testing. Seems like it could possibly be integrated into the classroom, and interest in sports and steroids is high.