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# Gases

## Introduction to one of the four states of matter that has no fixed volume or shape.

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Pop Rock Explosion

### Pop Rock Explosion

Credit: " apium"
Source: http://www.flickr.com/photos/apium/4242052373/

Yum! Rock candy. Actually, it’s pop rock candy. It pops and fizzes as it melts in your mouth. Do you know why?

#### The Back Story

• The reason pop rocks pop is that they release gas as they melt. The gas is under pressure in tiny bubbles inside the candy.
• The gas is carbon dioxide, the same gas that fizzes out of soda (pop) when you open the can.
• How much pressure is the gas under in pop rocks or soda? There’s a widespread myth that if someone swallowed enough pop rocks and soda, the pressure of all that gas could cause the stomach to explode.
• Credit: Michelle Schrank, Amy
Source: https://www.flickr.com/photos/michelleschrank/7467046206 https://www.flickr.com/photos/amylovesyah/4407488395

Soda and pop rocks both contain carbon dioxide [Figure2]

• The Mythbusters TV show investigated this myth, as you can see in this video: http://www.youtube.com/watch?v=93vjY9RY4-k

#### Can You Apply It?

1. How are pop rocks made? How does high-pressure gas get inside the candy?
2. Gas always moves from an area of higher pressure to an area of lower pressure. How does this apply to the gas in pop rocks?
3. Describe the experiment the Mythbusters did to answer the question: Can pop rocks and soda cause the stomach to explode? What was the result of the experiment?
4. How does gas pressure explain what you observed in the Mythbusters’ experiment?

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