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Activation Energy

Certain chemical reactions require energy input to begin.

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Expiration Date

Expiration Date

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

Medicine bottles and boxes like this one typically have recommended storage temperatures and expiration dates. How does the manufacturer know when the medicine will expire? And what if anything does temperature have to do with it.

News You Can Use

  • Storing medicines at higher-than-recommended temperatures can cause them to degrade more quickly than they would at lower temperatures. This shortens their shelf life.
  • Credit: bradleypjohnson
    Source: http://www.flickr.com/photos/bradleypjohnson/5356330050/
    License: CC BY-NC 3.0

    Expired medicines may not work, they could also be hazardous to your health [Figure2]


  • Why does temperature affect shelf life? Activation energy is the answer. Watch this animation to see the role of activation energy in chemical reactions:


What Do You Think?

At the links below, learn more about activation energy and the shelf life of medicines. Then answer the questions that follow.

  1. What is activation energy?
  2. How is activation energy related to temperature?
  3. All medicines eventually degrade, or break down, over time. Chemical reactions occur that change the chemical makeup of the medicines. All chemical reactions have a characteristic activation energy. How might this information be used to predict the shelf life of a medicine at different temperatures?
  4. What is the expiration date on a medicine? What happens to medicines after they pass their expiration date? Do they lose their effectiveness? Do they become unsafe?
  5. If you read package labels, you will learn that most medicines should be stored in a cool, dry place away from light. They also should be stored out of reach of children and pets. What do you think? Based on these guidelines, where would be a good place to store medicines in your home?

Image Attributions

  1. [1]^ Credit: Juliancolton; Source: http://commons.wikimedia.org/wiki/File:Cough_medicine.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: bradleypjohnson; Source: http://www.flickr.com/photos/bradleypjohnson/5356330050/; License: CC BY-NC 3.0

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