Re: does cold water weigh more than hot and why

Cold water does weigh more than hot water because it is more dense at a 
colder temperature.  The strange thing about this behavior is that once the 
water freezes and forms ice, the ice is less dense than the water.  You can 
check our site for details about ice: 
Why does ice float in water


A lot of compounds get more dense as they get colder.  The simplest way to 
describe it is that as molecules get colder, these particles have less 
energy to move around and so become more 'ordered'.  Crystals are a good 
example of molecules that are in 'order' or well-aligned.  They have very 
rigid, predictable structures.  Gases are an example of molecules in chaos, 
and expand to fill whatever volume they can.

I hope this information has helped a bit.

Kieran