How does Charles's Law describe gas behaviour?

Charles's Law states that the volume of a gas is directly proportional to its temperature, provided pressure is constant.

To understand Charles's Law better, let's break it down. Imagine you have a balloon filled with gas. If you heat the balloon, the gas particles inside it gain energy and move faster. As they move faster, they push outwards more forcefully, causing the balloon to expand. This is because, according to Charles's Law, when the temperature of a gas increases, its volume also increases, as long as the pressure remains the same.

Mathematically, Charles's Law can be written as \( V \propto T \) or \( \frac{V}{T} = k \), where \( V \) is the volume, \( T \) is the temperature in Kelvin, and \( k \) is a constant. This means that if you know the volume and temperature of a gas at one state, you can predict its volume at another temperature using the formula \( \frac{V_1}{T_1} = \frac{V_2}{T_2} \).

For example, if you have a gas at 300 K (Kelvin) with a volume of 2 litres, and you heat it to 600 K, the volume will double to 4 litres, assuming the pressure stays the same. This relationship helps us understand how gases behave under different temperature conditions, which is crucial in many scientific and industrial applications.

It's important to remember that temperatures must always be in Kelvin when using Charles's Law. To convert from Celsius to Kelvin, simply add 273.15 to the Celsius temperature. So, if you have a temperature of 25°C, in Kelvin it would be 298.15 K.

Charles's Law is a fundamental principle in the study of gases and helps us predict how gases will respond to changes in temperature, making it a key concept in GCSE Physics.