Cool it down!


1. A cup made of paper
2. Some water with room temperature (25 degrees)
3. A scientific thermometer (Can be obtain from any science supply store)
4. One tablespoon of Epsom salts (Warning: Direct contact with this salt can be harmful)


1. Put some tepid water into the paper cup. Fill up half of the paper cup.
2. Use the scientific thermometer to measure the temperature of the tepid water.
3. Now record the temperature.
4. Add some Epsom salts to the cup of water and stir it.
5. Feel the temperature of the side of the cup with your hands.
6. If you notice any change in temperature record it.
7. After a couple of minutes measure the temperature of the mixer of Epsom salt and water.
8. Now record the temperature.


When the Epsom salts mix with the tepid water, the temperature of the mixer decreases.


In this experiment heat is used to cause the chemical reaction to occur. This fine experiment is a very good example of an endothermic reaction. The term endothermic means that heat is absorbed when chemical reaction takes place. Epsom salts are actually magnesium sulfate which is a type of salt. When Epsom salts are mixed with water the magnesium sulfate uses heat to split into magnesium ions and sulfate ions in order to dissolve into the water it is mixed in with. Because this reaction uses heat the temperature of the water goes bellow.


When chemical bonds are created it always has to do something with energy. In some chemical reactions energy is used and on the other hand in some chemical reactions energy is released. When energy is used heat is absorbed and when energy is released heat is also being released. With magnesium sulfate in the mixer energy is used up when the chemical bonds between the ions of magnesium and sulfate are broken. This causes the heat in the surroundings to be absorbed.


1. Use double and also triple amount of Epsom salts and record what happens.
2. Use half and also one fourth amount of Epsom salts and record what happens.
3. Try this experiment using other kinds of salts.


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