• Question: You said that ice was less dense than water, but then why does it weigh more than water if there is the same amount of both?

    Asked by emma014442 to James_M on 23 Jun 2011.
    • Photo: James M Monk

      James M Monk answered on 23 Jun 2011:

      It depends what you mean by “amount.” If you mean volume then for the same volume the ice weighs less. This is why ice floats; it displaces a volume of water with a mass greater than the mass of the ice.

      Water is a really strange substance. For most compounds the solid state is more dense than the liquid state. Water is the exception because of the way the lattice in the ice crystal forces the water molecules further apart. I think it’s to do with the nature of the bend in the water molecule, so the hydrogen-oxygen bond on adjacent water molecules tries to line up.