If a chemical change can cause heat (exothermic), can another chemical change make something cold?
Things Required:
A thermometer
1 tablespoonful of Epsom salts
Tap water, neither hot nor cold
Spoon
A medium-size jar
Pencil and paper
Directions:
Fill the jar with tap water. Place the thermometer in the water. With your hand, feel the coolness of the jar while you wait until the thermometer registers the temperature of the water. Write the temperature down. Now stir in the Epsom salts. Feel the jar again. Is there a change? After a couple of minutes, take out the thermometer and record the temperature again.
This Is What Happens:
The jar feels slightly colder, and the temperature of the water after the chemical change is actually lower.
Science Behind It:
In the previous experiment “Exothermic Experiment,” a chemical change produced heat energy. But sometimes heat is instead used up in the chemical change. When Epsom salts, or magnesium sulphate is added to water, it uses the natural heat energy of the water to split apart ions of sulphate and magnesium. (Ions are positive or negative electrically charged atoms that occur when electrons are lost or gained.)
The chemical change in this experiment is called endothermic because more heat energy is being used up than is being produced. This is why the water gets colder, and why Epsom salts is used to soak a sprained ankle and draw the heat out of an injury.
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