How to Detect Signs of Chemical Reactions
A chemical reaction occurs when two or more substances chemically combine to form an entirely new substance. Sodium is a metal and chlorine is a poisonous gas, but thanks to chemical reactions they can combine to form sodium chloride, the salt we use on our food. Signs that a chemical reaction is occurring are usually easy to detect. A gas may be given off, like the poisonous gas formed with the combination of chlorine bleach and ammonia. Light or heat may be given off like that of a bonfire. A color change may occur, like when a hamburger browns on a grill.
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Things You'll Need
- Thermometer
- Black construction paper
- White construction paper
- Tape
- Vinegar
- Baking soda
- Resealable quart-size plastic freezer bag
- Safety goggles
Instructions
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Detecting a Chemical Reaction
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1
Make a background using the black and white paper. This can be as simple as taping them next to each other on a wall. You will be able to hold your experiment in front of each to better see if there are gases given off.
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2
Wearing safety goggles, hold the plastic bag so that one closed corner is pointing straight down.
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3
Place the thermometer inside the bag, so that the bulb is in the bottom corner. You will need to be able to read the thermometer through the bag.
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4
Scoop two or three tablespoons of baking soda into the bag. If some of the baking soda obscures the numbers on the thermometer, wipe it off and re-insert before adding the vinegar.
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5
Add one-fourth cup of vinegar into the bag, a little at a time, and watch it fizz! Feel the outside of the bag with your hand, and you will be able to feel the temperature rise, as you see it increase on the thermometer. The fizzing and bubbling is from carbon dioxide gas being formed.
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Tips & Warnings
Be careful not to confuse gas with steam, which comes off boiling water, and is only a change of state, from liquid to gas, not a new substance. If baking soda and vinegar are combined, the mixture will become warm, even though no heat was added from the stove or a lab burner.
Do not seal the bag, unless you have permission to make a big mess, as the gas being formed will cause it to pop. When you are though, wash the contents down the sink and dispose of the bag.
