People Breathe Air - Or is it Water?

Are there water vapour in the air?
- Lim Feng Yi (age 11)
Tampines North Primary School, SIngapore

Lim - Yes! There can actually be a whole lot of water vapor in the air we breathe. The word for how much water vapor there is in the air is "humidity". And the warmer it is, the more humidity the air can hold. At room temperature, one cubic meter of air can hold as much as 20 grams of evaporated water! But you don’t have to believe me. Here’s something you can try to prove it to yourself... Take a cold can of soda or a glass of cold ice water and set it out in the air. The air around the glass is colder than the rest of the air, so it can hold less water vapor. And when the air can’t hold as much water vapor as it actually has, some of the water will condense into a liquid form. This is why you should see liquid water condensed on the outside of the glass or can. -Tamara

(published on 10/22/2007)

is water gas
- milen (age 8)
canada,on. miss

Nice question. Water can be a gas and it can be a liquid and it can be a solid. When it’s cold, it forms a solid, with the water mlecules arranged in a regular pattern that can’t bend or flow easily. When it’s hot and the pressure is low the molecules fly apart, forming a gas. In between, the molecules stick together, but in a loose, irregular, tumbling sort of way- that’s a liquid.

Ordinarily at room temperature in the atmosphere, some water can be liquid so long as there’s enough water in the gas too. When there’s just enough water in the gas, the molecules jumping out of the liquid into the air are just balanced by ones coming from the gas into the liquid.

Mike W.

(published on 10/22/2007)