Q:

# What happens to density as temperature increases?

A:

In general, matter expands with rising temperature, which leads to a fall in density. However, there are important exceptions, such as the case with water when it transforms from the solid to the liquid state. Its molecules contract, leading to both a fall in density and a rise in density.

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Credit: Jelene Morris CC-BY 2.0

The ideal gas law, PV = nRT, shows that for gases, volume increases with an increase in temperature, which means that density falls. "P" is pressure, "V" is volume, "n" is number of moles and "R" is a constant. The equation shows that if number of moles and pressure are kept constant, an increase in temperature leads to an increase in volume. On the other hand, the equation "density = mass/volume" shows that for other matter, such as pure liquids and solids, density still tends to fall with increasing volume, as most matter expands with a rise in temperature anyway. This shows that, bar a few exceptional cases, density falls with an increase in temperature.

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## Related Questions

• A:

Density is measured by an object’s mass to volume ratio. The formula, which is expressed as density=mass/volume, quantifies how much matter is packed into the underlying object or space. Density is often measured in kilograms per cubic meter.

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Air density is the mass of air per unit of volume it occupies, and it is expressed in kilograms per cubic meter when using the metric system. In the free atmosphere, air density decreases when temperature increases or when the air is humid. However, air density increases when pressure increases.

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The density of a pencil varies based on the type of pencil, but it can be found by measuring the pencil's mass, preferably in grams, and then dividing the mass by the volume. The formula for density is density = mass/volume.