The Law of Conservation of Energy states that energy can change forms, but the total amount of energy always remains constant.
It doesn’t disappear or increase — it simply transforms.
Car Air Conditioner and the Law of Conservation of Energy
A car’s air conditioner uses a special gas called refrigerant to cool the inside of the vehicle.
The basic principle is the same as a home air conditioner, and both follow the law of conservation of energy.
A car air conditioner does not create cold air. Instead, it moves heat from inside the car into the refrigerant and then carries it outside.
It works by transferring heat, not by producing cold air.
How Refrigerant Moves and Changes Energy
Refrigerant is a gas that carries heat.
It changes between a gas and a liquid to move heat from inside the car to the outside.
- Compressing the refrigerant gas into high-pressure gas
The compressor squeezes the refrigerant gas into a smaller space. This makes the molecules collide more, causing the temperature to rise. - Releasing heat and turning high-pressure gas into high-pressure liquid
The hot, high-pressure gas passes through the condenser (a heat exchanger), where it releases heat outside and cools down into a high-pressure liquid. - Reducing pressure to turn high-pressure liquid into low-pressure liquid
When the compressed refrigerant is released into a larger space, it quickly expands. - Low-pressure liquid turns into gas
At this point, the refrigerant uses its own energy (called latent heat of vaporization) to absorb heat from the surroundings, which cools it down.
“Latent heat” means that during vaporization, heat is taken from the surroundings causing cooling.
The refrigerant absorbs heat as it changes into a gas. When air passes over this cold refrigerant, the air cools and blows into the car as cold air.
The refrigerant repeats this cycle of being compressed into a liquid and then expanding back into a gas, carrying heat along the way.
This cycle is a loop of:
high-pressure gas → high-pressure liquid → low-pressure liquid → low-pressure gas → and so on.
By moving heat with the refrigerant, the form and location of energy change, but the total amount of energy stays the same.
This shows the law of conservation of energy in action.