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Exothermic Reactions

Chemical reactions that release energy as a product.

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Hot and Cold

Hot and Cold

Credit: Boldie
Source: http://commons.wikimedia.org/wiki/File:Sprained_foot.jpg
License: CC BY-NC 3.0

Ouch! You’re playing soccer and your foot twists under you. The doctor says you’ve sprained your ankle. She tells you to put a cold pack on it for 20 minutes at a time over the next few days. Then you can alternate between cold and hot packs if you’re still having pain and stiffness.

News You Can Use

  • You’ve probably used cold or heat for pain or an injury. The cold reduces swelling and pain; the heat increases blood flow and reduces stiffness. Both have their place in treatment.
  • Credit: US CPSC
    Source: http://www.flickr.com/photos/uscpsc/7349054524/
    License: CC BY-NC 3.0

    Icepacks come in all shapes and sizes [Figure2]

  • Did you ever wonder how those amazing instant hot and cold packs work? Watch the experiments in this video to see how chemical reactions provide the answer: http://www.youtube.com/watch?v=-lHZg0tMdVU

Can You Apply It?

Learn more about instant hot and cold packs at the link below. Then answer the following questions.

  1. What type of chemical reaction occurs in a cold pack? Define this type of reaction. How is the reaction started in a cold pack?
  2. In the cold pack experiment in the video, what chemicals were used in the chemical reaction? What happened when they were mixed together? What did the beaker represent? How did the temperature of the beaker change?
  3. What type of chemical reaction occurs in a hot pack? Define this type of reaction. How is the reaction started in a hot pack?
  4. Describe the hot pack experiment in the video. Which part of the experiment represents what happens when a hot pack is used? How did the temperature of the beaker change?

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Image Attributions

  1. [1]^ Credit: Boldie; Source: http://commons.wikimedia.org/wiki/File:Sprained_foot.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: US CPSC; Source: http://www.flickr.com/photos/uscpsc/7349054524/; License: CC BY-NC 3.0

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