Science Buddies: "Ask an Expert"

Dear Sir/Madam

Although this is not linked to a school project the matter has been much disputed between me and my friend recently. One of us believes that steam is a colourless gas and so cannot be seen by the human eye, however water vapour can be seen. The other believes that both steam and water vapour are a white gas and are both visible.

Yours faithfully

Alex Pollard
Aged 16
Manchester

Hello Alex,

This forum is intended for students, parents, and teachers working on K-12 science projects. There are more appropriate sites for help with homework or general science discussions.

That said, water vapor is water in the gas phase. Boiling is one way to produce water vapor, and water vapor produced this way is usually considered to be steam. Water in the gas phase (water vapor or steam) is invisible. In certain conditions water vapor (or steam) can condense to form tiny liquid droplets that are visible. Examples are clouds in the sky and the stream emitted from a tea kettle. So the “white gas” that you see is actually the liquid droplets that condense from the gas phase.

A. Norman

Thank you very much for your reply, especially as it was not linked to a science project.

Nice to know that we were both wrong as now neither one of us can be smug towards the other. Had one of us been right and the other wrong I imagine we would have ended up hating each other (it's happened before).

Yours in gratitude

Alex