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Prebreathe

An astronaut wearing an EVA space suit

Astronauts use an EVA (extravehicular activity) suit or space suit when they go outside the International Space Station.

Before putting on the EVA suit, astronauts participate in prebreathing activities.

By prebreathing pure oxygen the astronauts purge nitrogen gas from their bodies.

A glass of soda bubbling because sugar has been dropped into it

When you open a can of soda, what do you hear? Fizzing.

A can of soda gets its fizz because it is supersaturated (more highly concentrated than is normally possible under given conditions of temperature and pressure) with carbon dioxide gas once it is open.

The pressure of the carbon dioxide dissolved in the liquid is greater than the pressure of the air surrounding it. This causes the carbon dioxide to move from the liquid to either the air in the can or to small bubbles in the liquid.

Water molecules are attracted to each other more than to carbon dioxide so carbon dioxide gets forced out when the pressure is decreased.

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