In an earlier post, I discuss some of my unit planning that (I hope!) further breaks down a few of these misconceptions - my students are not teaching themselves on google. They are weaving back and forth between learning content and the larger reason for learning the content.
However, every single one of these comments above are valid. It is really difficult work to ultimately balance individual accountability and group accountability. Every student needs to master basic stoichiometry before they leave my general chemistry course.
One challenge I have is knowing how to evaluate labs properly. In writing my new lab manual, I am setting up rubrics for each lab. The ultimate goal is for this manual to be used by all instructors across the chemistry department at our community college, so they need to have a consistent grading system. Writing these rubrics has been challenging.
First, I had my students examine the conductivity of a puddle of water the size of a nickel. They checked for conductivity. Then they took a very small amount of sodium carbonate and a fresh puddle of water and pushed in a few crystals from the side. You can still see the crystals in the water but it tested positive for conductivity. They had to explain this. They did the same with a fresh puddle of water and a few crystals of copper (II) sulfate. Again, it tested positive for conductivity but they could still see the blue crystal. Finally, they started again with another fresh puddle of water, pushed a few crystals of sodium carbonate on one side and on the opposite side they pushed in a few crystals of copper (II) sulfate. After waiting five minutes, a solid dull blue precipitate formed in the middle. Also, the drop tested positive for conductivity.
Are kids learning? Given the time it takes to implement and grade the activity, do I get a lot of "educational moments" out of it? Does it fit into the culture of the classroom? Is there a great deal of "conceptually rich" material in the activity that students can build on? I believe that two activities I tried this week fit the bill.
I love the periodic table. I love the order, the stories, the trends and patterns, the people who made it. I love how it can be used. I love that it is the ultimate cheat sheet for a scientists or a student taking chemistry. I love the different types of periodic tables that exist. My love for this table is pretty evident. I have four periodic table ties and a periodic table bow tie. My wife went to Florida for a week to take care of her sick mother and while she was gone, I bought a periodic table shower curtain. I learned two things pretty quickly. Eight year old boys can't keep secrets (my son specifically) and as much as my darling wife loves me, she drew the line on the shower curtain. It was her or the shower curtain. So, I took it to school and tried to put it in the one place that made sense...next to the safety shower.
You can perform an orange to black chemistry demonstration using materials commonly found in stores. The reaction appears to be similar to the Old Nassau reaction, but uses greener reagents. This is a great demonstration to do around Halloween time.
There is a hydrate lab which is done by many teachers. Typically, students first use a known hydrate and are provided the formula. As an example, they might use CuSO4. 5H2O. On paper, they would work through the percent by mass of water in copper (II) sulfate pentahydrate. They then would be given a mass of the copper (II) sulfate pentahydrate, calculate how much water they should lose and then they would heat it and compare the data with the calculated value. Next, they are given an unknown hydrate. They are also given the molar mass of the unknown salt of the hydrate and they have to calculate the molar ratio of salt to water based on their data. Here is one possible way to “tweak” this lab.