Which of the following is true about isolated system?

Options

A. Heat passes into or out of the system
B. Matter enters or leaves the system
C. Work can be done on the system
D. All are correct

Answer

To determine which statement is true about an isolated system, we first need to understand the characteristics of different types of systems in thermodynamics.

### Step-by-Step Solution:

1. **Define an Isolated System**: An isolated system is a type of thermodynamic system where neither matter nor energy can be exchanged with the surroundings. This means that the system is completely sealed off from its environment.

2. **Differentiate Between System Types**:
- **Open System**: In an open system, both matter and energy can be exchanged with the surroundings. For example, a boiling pot of water where steam can escape and heat can be added.
- **Closed System**: In a closed system, energy can be exchanged, but matter cannot. An example would be a sealed container of gas that can be heated but does not allow gas to escape.
- **Isolated System**: In an isolated system, there is no exchange of matter or energy. An example is a thermos bottle that is perfectly insulated.

3. **Evaluate the Options**:
- **Heat passes into or out of the system**: This is false because an isolated system does not allow heat transfer.
- **Matter enters or leaves the system**: This is also false since matter cannot be transferred in or out of an isolated system.
- **Work can be done on the system**: This statement is true. While an isolated system does not allow energy transfer in the form of heat, work can still be done on the system by compressing it or applying pressure from the outside.

4. **Conclusion**: The correct statement about an isolated system is that work can be done on the system, even though there is no transfer of heat or matter.

### Final Answer:
The true statement about an isolated system is: **Work can be done on the system.**

---