Science Smarts: Let’s investigate epsom salts

By Patty Rooks on November 8, 2025.

Clumsy old me, the other day, somehow, I hurt my foot (actually three toes)..I do not know what I did BUT someone offered me some advice when they saw me hobbling around. They said, “Did you try soaking your foot in epsom salts?”

I have heard about them, but never really used them in the past. As I am staring at the bag, I think to myself, perhaps I should experiment a little bit before I try them on myself to see what this is all about. Let’s get started.

*Remember to ask an adult before doing this experiment.

Materials

– Epsom salts (available at a drug store)

– Room temperature water

– Measuring cup

– Measuring spoon

– Cooking/candy thermometer (one to use in liquids)

– Cup or a bowl

– Plastic spoon

– Pencil

– Notebook

Procedure

1. Measure 50 mL of water into the bowl.

2. Place the thermometer in the water and record the temperature in your notebook. Leave the thermometer in the bowl.

3. Measure 10 mL of Epsom salts and pour into the water. Mix well.

4. Observe the temperature of the mixture. Record this in your notebook.

5. Hold your hands on the outside of the bowl. What do you feel?

What is going on?

The thermometer should have shown a drop in temperature. When you touched the outside of the bowl with your hands, it should have been colder. This experiment produced an endothermic reaction, or a reaction that uses up heat. When all of the heat is used up, it feels cold.

Athletes use epsom salts when they have an injury or sprain as it draws the heat out of the muscles and soothes it with the cold.

Patty Rooks, senior scientific consultant Praxis Science Outreach Society. Praxis has moved! We are very fortunate to be located in the Community Futures Entre Corp Building at #202 556 Fourth St. SE, Medicine Hat, Alberta, T1A 0K8. For all your science needs, please email praxis@praxismh.ca.

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