# How does density change with temperature?

Apr 14, 2014

With few exceptions, density decreases as temperature increases.

Density is mass divided by volume.

Density = $\text{mass"/"volume}$

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

The most common exception is liquid water. Its density increases on warming from 0 °C to 4 °C and then decreases at higher temperatures.

EXAMPLES

At 0°C, 1000.0 g of water have a volume of 999.8 mL.

∴ Density = $\left(1000.0 \text{ g")/(1000.3" mL}\right)$ = 0.9997 g/mL

At 4 °C, 1000.0 g of water have a volume of 1000.0 mL.

∴ Density = $\left(1000.0 \text{ g")/(1000.0" mL}\right)$ = 1.0000 g/mL

At 70 °C, 1000.0 g of water have a volume of 1022.7 mL.

∴ Density = $\left(1000.0 \text{ g")/(1022.7" mL}\right)$ = 0.9778 g/mL