**Temperatures in Kelvin**

The temperature scale that we most commonly use is Celsius. Celsius temperature is based on the melting point (0°C) and boiling point (100°C) of water. In science, we often use another temperature scale called **Kelvin (K)**.

**At 0 K, all matter has no energy**, so the movement of the particles of substances is minimized. Since there is no energy to lose for substances, temperature cannot go below 0 K. 0 K is equivalent to -273°C.

The conversion between Celsius and Kelvin temperature is:

**K = °C + 273**

**°C = K - 273**

**Volume and Pressure in Gases**

**When volume of gas decreases, the pressure increases**. In a smaller volume of gas, the gas particles collide more frequently with the walls of the container, thus increasing the pressure exerted by the gas.

**Similarly, when volume of gas increases, the pressure decreases**. In a larger volume of gas, the gas particles collide less frequently with the walls of the container, thus decreasing the pressure exerted by the gas.

**The volume and pressure in gases are inversely proportional.**

The equation summarizing this relationship is called **Boyle's Law**:

**P _{1}V_{1} = P_{2}V_{2}**

**given that the temperature remains constant**

P_{1} = pressure in state 1

_{V1} = volume in state 1

P2 = pressure in state 2

_{V2} = volume in state 2

**Volume and Temperature in Gases**

When the gas is heated, gas particles gain kinetic energy. The gas particles move faster, and the volume of gas becomes larger.

Conversely, when the gas is cooled down, gas particles lose kinetic energy, move slower, and the volume of gas shrinks.

**The volume and temperature in gases have a proportional relationship.**

The equation summarizing this relationship is called **Charles' Law**:

**V _{1} / T_{1} = V_{2} / T_{2}**

**given that the pressure remains constant**

_{V1} = volume in state 1

_{T1} = temperature in state 1 (K)

V2 = volume in state 2

_{T2} = temperature in state 2 (K)

**Pressure and Temperature in Gases**

If volume of gas remains constant and gas is heated, gas particles will collide more frequently with the walls of the container. This will increase the pressure of gas.

If gas is cooled down, gas particles will collide less frequently with the walls of the container. This will decrease the pressure of gas.

**Pressure and temperature in gases have a proportional relationship.**

The equation summarizing this relationship is called **Gay-Lussac's Law**:

**P**_{1}** / T**_{1}** = P**_{2}** / T**_{2}

**given that the volume remains constant**

_{P1} = pressure in state 1

_{T1} = temperature in state 1 (K)

P2 = pressure in state 2

_{T2} = temperature in state 2 (K)