A well stoppered thermos flask contains hot water .This is an example of

Options

A. closed system
B. open system
C. isolated system
D. non thermodynamic system

Answer

To solve the question regarding the type of system represented by a well-stoppered thermos flask containing hot water, we will analyze the definitions of the three types of thermodynamic systems: open, closed, and isolated systems.

### Step-by-Step Solution:

1. **Understand the Types of Systems**:
- **Open System**: In an open system, both mass and energy can be exchanged with the surroundings. For example, a cup of hot tea loses heat to the environment and can also lose mass if some tea spills out.
- **Closed System**: In a closed system, energy can be exchanged with the surroundings, but mass cannot. An example would be a sealed container of gas that can transfer heat but does not allow gas to escape.
- **Isolated System**: In an isolated system, neither mass nor energy can be exchanged with the surroundings. An example is a perfectly insulated container where heat cannot escape, and no mass can enter or leave.

2. **Analyze the Thermos Flask**:
- A thermos flask is designed to minimize heat transfer between its contents (hot water) and the environment. It is well insulated to prevent heat loss.
- Since the thermos flask is stoppered, it does not allow heat (energy) to escape and also does not allow any mass (water) to leave the flask.

3. **Determine the Type of System**:
- Given that the thermos flask does not exchange heat or mass with the surroundings, it fits the definition of an **isolated system**.

4. **Conclusion**:
- Therefore, the correct answer to the question is that a well-stoppered thermos flask containing hot water is an example of an **isolated system**.

### Final Answer:
A well-stoppered thermos flask containing hot water is an example of an **isolated system**.