Short Answer:

Charles’s law states that the volume of a gas is directly proportional to its temperature, provided the pressure and the amount of gas remain constant. This means that when the temperature of a gas increases, its volume also increases, and when the temperature decreases, the volume decreases.

This law helps us understand how gases expand when heated. For example, a balloon expands when heated because the gas inside it expands. Charles’s law is important in many engineering applications where temperature changes affect gas volume.

Detailed Explanation:

Charles’s law

Charles’s law is a basic gas law in thermodynamics, discovered by Jacques Charles in the 18th century. It explains the relationship between temperature and volume of a gas when the pressure remains constant. This law is very useful in understanding the behavior of gases in engines, airships, hot-air balloons, and other thermal systems.

Statement of Charles’s Law

“The volume of a fixed amount of gas is directly proportional to its absolute temperature, provided the pressure remains constant.”

Mathematically:

V ∝ T
or
V / T = constant

So,

V₁ / T₁ = V₂ / T₂

Where:

V₁ = Initial volume
T₁ = Initial temperature in Kelvin
V₂ = Final volume
T₂ = Final temperature in Kelvin

Note: Temperature must be in Kelvin for this formula to work correctly.

Real-Life Example of Charles’s Law

Hot Air Balloon Example:

When the air inside a hot-air balloon is heated, its temperature increases.
As per Charles’s law, the volume of the air expands.
This makes the balloon lighter than the surrounding cooler air, so it rises.

This is a perfect example of Charles’s law in real-world use.

Another Example: Balloon in Freezer

Take a balloon filled with air at room temperature.
Place it inside a freezer.
As the temperature decreases, the volume of the balloon shrinks.
This happens because the gas molecules inside move slower and occupy less space.

This shows how gas volume is directly linked to temperature.

Graphical Representation

A graph of Volume (V) vs Temperature (T) is a straight line.
The line starts from the origin (0,0) if temperature is in Kelvin.
It shows that as temperature increases, volume also increases.

Applications of Charles’s Law

Hot-air balloons – Rise due to heated air expanding.
Air conditioning systems – Gas volume changes during temperature cycles.
Tyre pressure changes – Volume and pressure change with outside temperature.
Gas storage systems – Safe storage depends on temperature and volume control.
Weather balloons – Expand as they rise and experience lower temperatures.

Limitations of Charles’s Law

Assumes gas behaves as an ideal gas.
Not accurate for real gases at very low temperatures or very high pressures.
Only valid when pressure remains constant and no gas escapes.

Despite these limitations, Charles’s law works well in everyday conditions and is used in many mechanical systems.

Conclusion

Charles’s law explains the direct relationship between the volume of a gas and its temperature at constant pressure. When temperature increases, gas expands; when it decreases, gas shrinks. This law is very useful in understanding and designing systems involving gases and temperature changes. Whether it’s a hot-air balloon or a car tyre, Charles’s law helps predict how gas volume will behave with temperature changes.