Which is an open system ?

Options

A. Preparation of steamed rice in sealed vessel.
B. Gas filled in refrigerator for refrigeration cycle.
C. Cooling by desert cooler.
D. Hot tea.filled in Thermos flask

Explanation

To determine which option represents an open system, we first need to understand the definition of an open system in thermodynamics.

### Step-by-Step Solution:

1. **Define Open System**: An open system is one that can exchange both matter and energy with its surroundings. This means that substances can enter or leave the system, and energy can be transferred in or out.

2. **Evaluate Each Option**:
- **Option A**: Preparation of steam in a sealed vessel.
- **Analysis**: A sealed vessel does not allow matter (steam) to escape or enter, thus it is a closed system.
- **Conclusion**: This option is not an open system.

- **Option B**: Gas filled in a refrigerator for refrigeration cycle.
- **Analysis**: The gas is contained within the refrigerator, which is designed to keep the gas from escaping. Therefore, it does not allow for the exchange of matter with the environment.
- **Conclusion**: This option is also a closed system.

- **Option C**: Cooling by a desert cooler.
- **Analysis**: A desert cooler works by drawing air through wet pads, allowing moisture to evaporate and cool the air. This process involves the exchange of air (matter) with the surroundings, making it an open system.
- **Conclusion**: This option is an open system.

- **Option D**: Hot tea filled in a thermos flask.
- **Analysis**: A thermos flask is designed to minimize heat transfer and keep the contents hot, effectively sealing the tea inside. Therefore, it does not allow for the exchange of matter or energy with the environment.
- **Conclusion**: This option is a closed system.

3. **Final Conclusion**: The only option that qualifies as an open system is **Option C: Cooling by desert cooler**.