When gas in a vessel expands, it thermal energy decreases. The process involved is

Options

A. Isobaric
B. Isochoric
C. Isothermal
D. Adiabatic

Answer

To solve the question regarding the process involved when the gas in a vessel expands and its thermal energy decreases, we can analyze the given options step by step.

**Step 1: Understand the given options.**
The options provided are:
1. Isobaric
2. Isochoric
3. Isothermal
4. Adiabatic

**Hint:** Familiarize yourself with the definitions of each thermodynamic process to identify which one fits the scenario.

**Step 2: Analyze the meaning of thermal energy decrease during expansion.**
When a gas expands, it does work on its surroundings. If the thermal energy of the gas decreases, it indicates that the internal energy of the gas is being utilized for this work rather than being maintained or increased.

**Hint:** Recall that internal energy is related to the temperature and the amount of work done by the gas during expansion.

**Step 3: Consider the nature of the expansion process.**
In an adiabatic process, there is no heat exchange with the surroundings (ΔQ = 0). This means that all the work done by the gas comes from its internal energy, leading to a decrease in thermal energy.

**Hint:** Think about what happens in a fast expansion—there is often insufficient time for heat exchange with the environment.

**Step 4: Evaluate the other options.**
- **Isobaric**: This process occurs at constant pressure, and heat can be exchanged with the surroundings, which would not lead to a decrease in thermal energy.
- **Isochoric**: This process occurs at constant volume, meaning no work is done, and thus thermal energy would not decrease.
- **Isothermal**: This process occurs at constant temperature, meaning internal energy remains constant and thermal energy does not decrease.

**Hint:** Eliminate options that do not match the condition of thermal energy decreasing during expansion.

**Step 5: Conclude the correct answer.**
Since the gas expands rapidly, leading to a decrease in thermal energy without heat exchange, the correct process is an **adiabatic process**.

**Final Answer:** The process involved is **adiabatic**.

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