Question

Why does density change with temperature?

Answer 1

Density changes with temperature because volume changes with temperature.

Density is mass divided by volume.

Density = `(mass)/(volume)`

As you heat something up, the volume usually increases because the faster moving molecules are further apart. Since volume is in the denominator, increasing the volume decreases the density.

EXAMPLES

At 10 °C, 1000.0 g of water have a volume of 1000.3 mL

∴ Density = `(1000.0 g)/(1000.3mL)` = 0.999 70 g/mL

At 70 °C, 1000.0 g of water have a volume of 1022.73 mL

∴ Density = `(1000.0 g)/(1022.7 mL)` = 0.977 78 g/mL