Gases

Definition

Gases are one of the states of matter characterized by low density and high compressibility, with molecules in rapid random motion. They have no fixed shape or volume, expanding to fill their containers.

5 Must Know Facts For Your Next Test

1. The behavior of gases can be described by the ideal gas law: $PV = nRT$, where $P$ is pressure, $V$ is volume, $n$ is the number of moles, $R$ is the universal gas constant, and $T$ is temperature.
2. Gases exert pressure on the walls of their containers due to collisions of molecules with the container walls.
3. Boyle's Law states that for a given mass of gas at constant temperature, pressure and volume are inversely proportional: $P \propto \frac{1}{V}$.
4. Charles's Law indicates that at constant pressure, the volume of a gas is directly proportional to its absolute temperature: $V \propto T$.
5. Avogadro's Law states that equal volumes of all gases at the same temperature and pressure contain an equal number of molecules.

Review Questions

• What equation describes the relationship between pressure, volume, temperature, and number of moles in an ideal gas?
• How does Boyle's Law relate pressure and volume for a gas at constant temperature?
• According to Charles’s Law, what happens to the volume of a gas when its temperature increases while keeping pressure constant?

Related terms

Pressure:

The force exerted per unit area by gas particles colliding with the walls of their container.

Density:

The mass per unit volume of a substance; for gases, it varies with temperature and pressure.

Ideal Gas Law:

$PV = nRT$, an equation representing the state behavior of an ideal gas relating its pressure (P), volume (V), amount (n), universal gas constant (R), and temperature (T).