Ice floats on water because it has a lower density than water.

If d and T are, respectively, the water density and temperature, This is a really unusual property.

Other substances whose density decreases when they freeze are gallium, germanium, silicon and acetic acid.

then, close to the freezing point where a0 = 999.8, a1 = 16.95, a2 = −7.987 × 10−3 and b1 = 16.898

× 10−3

(Kell, 1975).

We haven’t put in units for a0 etc, as you have to work those out as part of the question.

a. If d is in units of kg m−3 and T is in units of ◦C, what are the units of a0, a1, etc?

b. At what temperature does water attain its greatest density, and what is the value of this density?

c. How does this explain why ice floats on water?