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Two or more elements combined in a fixed proportion.

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Coffee and Compounds

Coffee and Compounds

Credit: User: Flickr upload bot
Source: http://commons.wikimedia.org/wiki/File:2_coffee_drinks.jpg
License: CC BY-NC 3.0

Coffee is a great way to start a morning, and an example of a compound [Figure1]

Compounds are a unique substance that form when two or more substances chemically combine. Although the properties of different compounds varies, a specific compound will always have the same elements in the same proportions no matter what. 

Imagine you’re brewing a pot of coffee. If you add too much hot water, the coffee will be too weak, but if you add too many coffee grounds, the drink will be too strong. This coffee is an example of a mixture because the it can be made from various amounts of coffee and water, the coffee and water retain their properties when mixed, and can be made from physical means.

The caffeine in a coffee, however, is an example of a  compound.

Credit: Paginazero
Source: http://commons.wikimedia.org/wiki/File:Caffeina_struttura.svg
License: CC BY-NC 3.0

The structure of a caffeine molecule. [Figure2]

Adding another oxygen atom to the composition of caffeine won’t result in “more oxygenated” caffeine, but a new compound all-together. Thus, caffeine is a compound because it has a definite composition, the combined elements have lost their original properties, and caffeine cannot be created by physical means.

Creative Applications

1. When you add milk to your coffee, are you making a compound or mixture? 

2. How could you change the composition of caffeine? 

3. What are other examples of compounds?

Image Attributions

  1. [1]^ Credit: User: Flickr upload bot; Source: http://commons.wikimedia.org/wiki/File:2_coffee_drinks.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Paginazero; Source: http://commons.wikimedia.org/wiki/File:Caffeina_struttura.svg; License: CC BY-NC 3.0

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