Speaking of refrigeration and coldness, have you ever used one of those "instant cold packs" that looks like a plastic bag filled with liquid. You hit it, shake it up and it gets extremely cold. What's going on here?
The liquid inside the cold pack is water. In the water is another plastic bag or tube containing ammonium-nitrate fertilizer. When you hit the cold pack, it breaks the tube so that the water mixes with the fertilizer. This mixture creates an endothermic reaction -- it absorbs heat. The temperature of the solution falls to about 35 F for 10 to 15 minutes.
For more information on refrigeration and related topics, check out the links below.
- Who invented the refrigerator?
- How Food Preservation Works
- How does a frost-free refrigerator work?
- How Solar-powered Refrigerators Work
- Refrigerant Poisoning
- Quiz: Could you go without your refrigerator?
- Refrigerator and Freezer Basics and Minor Repairs
- Top 10 Appliances We Can't Live Without
- Top 10 Wacky Inventions for the Home
- 10 Appliances for Tight and Tricky Spaces
- How Refrigerators Work
- How Water Heaters Work
- Refrigerator Alternatives: Warm Green
More Great Links
- Casiday, Rachel and Regina Frey. "Phase Changes and Refrigeration: Thermochemistry of Heat Engines." Washington University. 1/2007. (6/13/11). http://www.chemistry.wustl.edu/~courses/genchem/LabTutorials/Thermochem/Fridge.html
- Castleden, Rodney. "Inventions that Changed the World." Chartwell Books, Inc. 2007
- FreeEd.net. "Fundamentals of Refrigeration: Common Refrigerants." (6/14/11). http://www.free-ed.net/sweethaven/MechTech/Refrigeration/coursemain.asp?lesNum=4&modNum=1
- Half a Handy. "How Your Refrigerator Works." 1/31/09. http://www.youtube.com/watch?v=1Z9LqQvuciQ
- Repair Clinic. "Refrigerator - How Things Work." (6/14/11). http://www.repairclinic.com/Refrigerator-How-Things-Work
- Time Magazine, "Great Inventions - Geniuses and Gizmos: Innovations in Our Time." Time Books: New York. 2003. (6/14/11)
- Woodford, Chris, Luke Collins, Clint Witchalls, Ben Morgan and James Flint. "Cool Stuff and How it Works. Korling Kindersley Limited. 2005.
- Woodford, Chris. "Refrigerators." Explain that Stuff. 5/18/11. (6/14/11). http://www.explainthatstuff.com/refrigerator.html