IDENTIFYING REACTANTS AND PRODUCTS
Since you now have an understanding of reactants and products. I want you to identify certain reactants and products in experiments you have already completed.
In the experiment described below, identify all the reactants, and identify at least one product of the experiment. (Hint: Refer to your match test. Remember that fire can only burn in the presence of oxygen. If your match illuminated brighter when placed near
the chemical reaction, the gas given off was oxygen. If your match was extinguished when it was placed near the chemical reaction, assume that the gas given off was carbon dioxide.)
It would be useful to have another person with you to watch the thermometer while you test the chemical reaction with the match, or you could repeat the experiment twice. Take an unlit match and using tape, attach it to something longer like a Popsicle stick, eating utensil, writing utensil, etc. (A long match stick would be perfect.) This will make it easier to place the match closer to the chemical reaction without burning your fingers. Place a cup in a sink. Place a teaspoon of baking soda in the cup with a thermometer. Pour a small amount of vinegar in the cup. Light a match and hold it near the surface of the vinegar where the chemical reaction is occurring. Correct fire safety procedure should be used at all times. After your chemical reaction is finished, dispose of the baking soda and vinegar solution down the sink.
In the experiment described below, identify all the reactants, and identify the gas that is given off as a product.
It would be useful to have another person watch your thermometer in this experiment as well. In a glass cup, place a tablet of Alkaseltzer or Efferdent. Tape another match on something that will extend its length. Place your thermometer in the cup. Pour the cup half full of water. As the chemical reaction occurs, light your match and stick it down into the foaming area. The byproducts of this reaction can also be disposed of down the sink.
***If you have not already read though the websites on writing and balancing chemical equations, you might want to go back and read them now.
We obviously know that soft drinks are “fizzy.” Have you ever wondered why? Soft drinks are made with carbonic acid (chemical formula HCO). Carbonic acid 23
decomposes into water (HO) and carbon dioxide (CO). The chemical equation for this 22
HCO ? HO + CO23 22
How many atoms of hydrogen are on the reactant side? How many atoms of hydrogen are on the product side? How many atoms of carbon are on the reactant side? How many atoms of carbon are on the product side? How many atoms of oxygen are on the reactant side? How many atoms of oxygen are on the product side? What is the pattern here? Is this pattern unusual or always the case and why?
Look at the products of the experiments you did in the “How do we identify chemical reactions?” section. If you need to, do some experiments again. If you were to “reuse” the products of your experiment as a reactant in the same experiment, what would happen? Do reactants and products typically have the same physical and chemical properties?
Explain how reactants and products are alike? How are reactants and products different?
We will go into more detail in the next assignment.