Science Buddies: "Ask an Expert"

Hello,

I am a 9th grade student and i need help with conducting an experiment. We want to test the question "Which holds more water vapor: warm air or cold air " but we don't know how we would or should do to test that. Can you please help?

Hi Layla1212,

Welcome to Science Buddies! I think you are doing this excellent project to make a psychrometer, which will measure relative humidity.


https://www.sciencebuddies.org/science- ... p011.shtml

You have a good question about the amount of water that can be absorbed by air. The amount of water in air is actually independent of air and temperature, and is actually an equilibrium between liquid water and the space above the water and it depends on the temperature of the liquid water.

Here is a website from a University of Maryland professor that answers the question in more detail. Please try reading this and let me know if you have questions.

http://www.atmos.umd.edu/~stevenb/vapor/

You may want to think more about what you want to accomplish with your science project. If you want to measure the absolute amount of water in air that is at different temperatures, you will need to design a different type of experiment. However, if you are interested in building the psychrometer, you could do many useful experiments measuring relative humidity.

A psychrometer measures relative humidity, which is not the same as water vapor content. So it cannot be used to measure the quantity of water in air. However, measuring relative humidity is very useful for monitoring the weather and other applications.

I realize this may be a little confusing, so please post more questions and let us know exactly what you want to do.

Donna