I’m going to make a few more targeted posts. I teaching another year of Biology for Co-op, but realize many of you need more Chemistry help. One tough topic is Percent Composition. Years ago I used a textbook with this section, 10.3, Percent Composition and Chemical Formulas. Scroll down for the Quick Lab. This excerpt has teacher notes for the lab with sample data. Copper sulfate and calcium chloride are both cheap chemicals. The blue version of copper sulfate is the hydrate. I use Epsom salts, magnesium sulfate, too. It produces loads of water! Be careful! If the label indicates the chemical is anhydrous, it means the water in the formula has been removed.
The Percent Composition Quick Lab works with a tea candle or Sterno. Ask kids heat the substance to remove the water, they should angle the test tube away from anyone and move the test tube back and forth in the flame. During COVID some kids did this lab on their gas stove with good results. One note: sometimes the salt won’t come out of the test tube after heating. Don’t forget to use Pyrex, Kymex,mor borosilicate test tubes. Always, always wear safety goggles or safety glasses. Below is a video for instruction.
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