Thermochemistry Demonstrations
See also: Heat
Thermochemistry is the study of the energy changes that accompany chemical reactions and physical transformations. This category highlights how heat is absorbed or released when substances react or change state. Exploring thermochemistry links the ideas of energy and matter, helping explain processes from burning fuels to dissolving salts.
| Demonstration | Materials | Difficulty | Safety | Summary |
|---|---|---|---|---|
| Flaming Gummy Bear | ★★★ | ★★★ | ★★★ | A gummy bear (or sugar sweet) is dropped into molten potassium chlorate, which decomposes to release oxygen. The sugar rapidly combusts, producing heat, light, gas, and a dramatic flame. |
| Sodium in Water | ★★★ | ★★★ | ★★★ | A pea-sized piece of sodium metal is placed on water, where it reacts exothermically to form sodium hydroxide and hydrogen gas. Heat from the reaction can ignite the hydrogen, and a pH indicator shows the solution becoming alkaline. |
| Instant Snow Polymer | ★★★ | ★☆☆ | ★★☆ | A small amount of instant snow polymer rapidly absorbs water and swells to many times its original volume, creating fluffy “snow and causing a temperature change. |
| Energy in Food | ★★☆ | ★★☆ | ★★☆ | A small piece of dry food is burned beneath a boiling tube containing water, and the rise in water temperature is measured. From this, the approximate energy released is calculated. |
| Endothermic and Exothermic Dissolving | ★★☆ | ★☆☆ | ★★☆ | This demonstration compares two reactions: one that absorbs heat from the surroundings (endothermic) and one that releases heat (exothermic). Students can observe changes in temperature and feel whether the container becomes hot or cold. |
| Steel Wool and Vinegar Exothermic Reaction | ★☆☆ | ★☆☆ | ★☆☆ | This experiment shows how rusting, a type of oxidation reaction, can release heat. When steel wool is soaked in vinegar, its protective coating is removed, allowing the iron to react more readily with oxygen. The oxidation produces heat, making this an example of an exothermic reaction. |
| Freeze a Beaker to a Board | ★★☆ | ★★☆ | ★★☆ | When ammonium nitrate and barium hydroxide are mixed, they undergo a strongly endothermic reaction that absorbs heat, lowering the temperature to around –25 °C to –30 °C. The beaker becomes so cold that water freezes, bonding the beaker to the wooden block beneath it. |
Materials
★☆☆ Easy to get from supermarket or hardware store
★★☆ Available in most school laboratories or specialist stores
★★★ Requires materials not commonly found in school laboratories
Difficulty
★☆☆ Can be easily done by most teenagers
★★☆ Available in most school laboratories or specialist stores
★★★ Requires a more experienced teacher
Safety
★☆☆ Minimal safety procedures required
★★☆ Some safety precautions required to perform safely
★★★ Only to be attempted with adequate safety procedures and trained staff