When a gas undergoes adiabatic expansion, it gets cooles. This is because

Options

A. It is an exothermic process
B. It is an endothermic process
C. Internal energy of the system decreases
D. Ideal gas becomes a real gas

Answer

**Step-by-Step Solution:**

1. **Understanding Adiabatic Expansion:**
- In an adiabatic process, there is no heat exchange between the system and its surroundings. This means that all the work done during the expansion comes from the internal energy of the gas.

2. **Internal Energy and Temperature Relationship:**
- The internal energy of an ideal gas is directly related to its temperature. As the gas expands adiabatically, it does work on the surroundings, which requires energy.

3. **Decrease in Internal Energy:**
- Since the gas does work during the expansion and there is no heat input from the surroundings, the internal energy of the gas decreases. This decrease in internal energy is a result of the energy used to do the work.

4. **Effect on Temperature:**
- As the internal energy decreases, the temperature of the gas also decreases. This is because the internal energy is a function of temperature for an ideal gas.

5. **Conclusion:**
- Therefore, during adiabatic expansion, the gas cools down because its internal energy decreases, leading to a drop in temperature.

**Final Answer:**
When a gas undergoes adiabatic expansion, it gets cooled because the internal energy of the system decreases, which in turn leads to a decrease in temperature.

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