Why are ice and steam white but water clear?

myfatherrsson

Always wanted to know.......also why does ice expand? somethin else i also wanted to know...

much obliged! XD

sink

Solid ice is as clear as glass, it is tiny bubbles of air trapped in the ice that give it it's white colour. Water vapour is also perfectly clear, it's only when it condenses due contact with cold air that the vapour turns into mist which appears white.

pisslips

I'd imagine ice is white because it's a rough surface with lots of tiny fractal ice structures on or near the surface. The light might reflect from these because maybe the disorder of the surface means that light entering the ice is greater than(or less than I can't remember) the critical angle and get's reflected.

Water in a liquid state is incompressible and has total freedom to find a ground state which would naturally mean a perfectly smooth unform surface since there would be no crystal structures, this is disregarding suface tension which would be pretty neglligible with regards the human eye.Most light entering the liquid would refract rather than reflecting back.

The steam similarly might reflect the light because it's small curved surfaces so something to do with the critical angle of the light again.

I can't really remember leaving cert anymore but this is my inclination anyway.

I'd also say that there is a lot of interference when the light enters these sufaces that are full of impurites, maybe this is why you get a white reflection.

I haven't a clue really.

sink

myfatherrsson wrote: »

Always wanted to know.......also why does ice expand? somethin else i also wanted to know...

much obliged! XD

Forgot to answer this question. It has to do with stable hydrogen bonds being formed at low temperatures causing the H2O molecules to form a rigid lattice structure which holds the molecules farther apart. At warmer temperatures hydrogen bonds are unstable and are not strong enough to keep the excited molecules from coming closer.

pisslips

Why is steam white?

like if i had a giant sphere of water it would be transparent wouldn't it?

A7X

pisslips wrote: »

Why is steam white?

like if i had a giant sphere of water it would be transparent wouldn't it?

You have to keep in mind how small these things are. Its more than likely to do with refracted light but I really don't know the answer.

Still A giant sphere of water would just appear different because of it's size obviously.

pisslips

yes but if i looked at the giant sphere of water from very far away I think I would recieve reflected rays of white light.

So whats the relation between the distance of the observer and the relative curvature of the surface......how come recieve more reflected rays and get less transparency(refracted rays) the further away I am?

I'm thinking convex mirror .....focal points...but I can't remember.

Professor_Fink

pisslips wrote: »

I'm thinking convex mirror .....focal points...but I can't remember.

Convex mirrors have focal points behind the mirror. They don't focus light.

kiffer

Water is blue

pisslips

Professor_Fink wrote: »

Convex mirrors have focal points behind the mirror. They don't focus light.

exactly so naturally a sphere of water is like infinite convex mirrors for light which enters at less than the critical angle.the light would be dispersed...

so the incident ray would have to be greater than the critical angle with repect to the tangent to the sphere at that point.Thats unlikely to happen for many rays travelling in paralell direction so a lot would be reflected.

Of course when steam is really hot and the particles are tiny, you can't see it all.It's only at certain sizes that it appears white.

Anyone?

Morbert

I believe Mie scattering is responsible for the whiteness of clouds and steam.

amen

Water vapour is also perfectly clear, it's only when it condenses due contact with cold air that the vapour turns into mist which appears white.

be careful but fill you kettle to the brim and boil

if you look carefully there will a thiny gap over the water may 1-2cm high that is clear and above this you see "steam" the clear gap is the actual boiled water vapour before it condenses

cianl1

kiffer wrote: »

Water is blue

He's right you know.http://en.wikipedia.org/wiki/Color_of_waterWe can't see it in small quantities, so it appears transparent, however pure water does have a light blue colour through selective absorption and scattering of the light spectrum."The light turquoise blue color is caused by weak absorption in the red part of the visible spectrum. Absorptions in the visible spectrum are usually attributed to excitations of the electronic energy states in matter. Water is a simple 3-atom molecule, H2O, and all its electronic absorptions occur only in the invisible ultraviolet region of the electromagnetic spectrum and therefore, cannot be responsible for the intrinsic water color."Also, to those people who think it's because of the reflection of the sky, what about when it's cloudy?