An example of closed system is :

Options

A. Hot liquid in closed beaker in equilibrium with its vapour
B. Hot liquid in an open beaker
C. Hot liquid in a sealed insulated beaker
D. None

Explanation

To determine an example of a closed system, we need to understand the definition of a closed system in thermodynamics. A closed system is one where energy can be exchanged with the surroundings, but matter cannot be exchanged.

### Step-by-Step Solution

1. **Understand the Definition of a Closed System**:
- A closed system allows for the exchange of energy (heat) but not matter. This means that while the system can gain or lose heat, the amount of substance within the system remains constant.

2. **Analyze the Options**:
- **Option 1**: Hot liquid in a closed beaker in equilibrium with its vapor.
- In this scenario, the beaker is closed, meaning that no matter can escape. The hot liquid can evaporate, and the vapor can condense back into the liquid, maintaining equilibrium. There is an exchange of energy (heat) with the surroundings, but no exchange of matter.
- **Option 2**: Hot liquid in an open beaker.
- Here, the beaker is open, allowing both heat and matter to escape. As the liquid evaporates, the level of the liquid decreases, indicating an exchange of matter.
- **Option 3**: Hot liquid in a sealed insulated beaker.
- In this case, the beaker is both sealed and insulated. While there is no exchange of matter, there is also no exchange of energy (heat) because the insulated boundary prevents heat transfer. This is an example of an isolated system, not a closed system.
- **Option 4**: None.
- This option suggests that none of the previous options represent a closed system.

3. **Identify the Correct Option**:
- Based on the analysis, **Option 1** (hot liquid in a closed beaker in equilibrium with its vapor) is the only scenario that fits the definition of a closed system. It allows for energy exchange while preventing matter exchange.

### Conclusion:
The correct answer is **Option 1: Hot liquid in a closed beaker in equilibrium with its vapor**.

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