Thursday, May 13, 2010

Instant Cold

Mix just a small amount of water with one chemical, and the temperature immediately drops to near freezing! Make your own instant Ice Packs. An easy and surprising experiment...

This experiment demonstrates an endothermic reaction. Water is added to Ammonium Nitrate and the temperature of the solution rapidly drops.

Chemicals Required:
- Ammonium Nitrate

Place approximately 100 mL of water in a large beaker or glass jar and record the temperature.
Quickly dump in 15 grams of Ammonium Nitrate and stir.
Note the temperature change as the Ammonium Nitrate dissolves.

The drop in temperature will be surprising and will continue to decrease for several minutes. Frequently the solution gets so cold that water vapor from the air begins to condense on the outside of the beaker.

Small zip-lock baggies of Ammonium Nitrate can be kept handy as cold packs. When needed, simply add water in any form and seal the bag for an instant cold pack.

- United Nuclear

Another recipe uses a mix of ammonium thiocyanate and barium hydroxide octahydrate added to water, which can produce an exteme endothermic reaction capable of freezing water (down to ~30° Celsius).


  1. can't you use different amounts of ammonium nitrate? Will the reaction change if you add more or less ammonium nitrate? Will it last longer?