An exothermic reaction occurs when energy is released, typically in the form of heat, light or sound. (Its opposite, an endothermic reaction, occurs when heat or other kinds of energy is absorbed). Exothermic reactions produce more energy, called output energy, than is required to set them in motion, called input energy. Here are a few science experiments that will make effective exothermic reaction projects. As always, exercise caution when using chemicals or other potentially hazardous materials.
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The simplest demonstration of an exothermic reaction occurs when something burns. A candle, for example, emits heat as it slowly burns, efficiently representing an exothermic reaction. A project can centre on feeling or measuring the heat output of a flame and discussing how and why the flame releases heat and light energy.
In a slightly more advanced project, an individual can dissolve sodium hydroxide in water as an exothermic project. As the water and sodium hydroxide interact, the sodium hydroxide will release heat as it dissolves. Once dissolved, the experimenter can't easily separate the two ingredients, so anyone undertaking this project should keep this in mind. Also known as lye, a student should handle sodium hydroxide with care.
Calcium Chloride, Baking Soda and Purple Cabbage Juice
For this exothermic project, a student should place a teaspoon of calcium chloride powder and a teaspoon of baking soda in a zip-lock bag. A half ounce of purple cabbage juice should be added to a small condiment cup and then placed into the zip-lock bag, taking care to not spill the liquid. Squeeze out all the extra air, and shut and seal the bag. Once sealed, the student should then empty the cabbage juice into the bag, either by pouring or shaking. The student should feel the temperature of the bag and record the results.
Yeast and Hydrogen Peroxide
This project involves using yeast and hydrogen peroxide to release heat. The student will require a 250 millilitre beaker, a thermometer, one tablespoon of quick-rising dry yeast and 1/4 cup of hydrogen peroxide. A student should begin by recording the room temperature on his thermometer and then place the thermometer in the beaker. Using a spoon, he should mix the peroxide and yeast in the beaker. Over a period of time the student may record the temperature and feel the heat released by the experiment on the sides and bottom of the beaker.
Handwarmers, a common staple of sports fans in the winter, are filled with iron oxide fillings and lend themselves naturally to exothermic science projects. For this project, a student will require a sealed bag of iron oxide and a new, unused handwarmer. With another resealable bag nearby, she should cut open the new handwarmer and empty the fillings into the bag, keeping the bag open. Upon inspection, the sealed bag of iron oxide fillings will feel about room temperature, while the open bag will feel warm. After this observation, the student should seal the bag and check its temperature again in a few minutes. Without oxygen to power the exothermic reaction, the freshly opened iron oxide fillings from the new handwarmer will no longer produce heat.
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- Science Project Ideas for Kids: Exothermic Reactions
- U.S. Department of Energy: Ask a Scientist: Endo, Exothermic Reactions and Energy
- Cal Poly Pomona: Supermarket Chemical Reactions in Zip Lock Bags
- Utah State Office of Education: Getting Warmer
- South Carolina Energy Office: The Experiments: Part II