A pressure cooker reduces cooking time because

Options

A. (a) the higher pressure inside the cooker crushes the food material
B. (b) cooking involves chemical change helped by a rise in temperature
C. (c) heat is more evenly distributed in the cooking space
D. (d) boiling point of water involed in cooking is increased

Answer

To understand why a pressure cooker reduces cooking time, let's break down the explanation step by step.

### Step-by-Step Solution:

1. **Understanding the Pressure Cooker**:
A pressure cooker is a sealed pot that cooks food quickly under high pressure. The key concept here is that as pressure increases, the boiling point of water also increases.

2. **Constant Volume**:
Inside a pressure cooker, the volume is kept constant. This means that the space inside the cooker does not change, which is important for understanding how pressure and temperature relate to each other.

3. **Gas Laws**:
According to the ideal gas law, \( PV = nRT \), where:
- \( P \) = pressure
- \( V \) = volume
- \( n \) = number of moles of gas
- \( R \) = universal gas constant
- \( T \) = temperature (in Kelvin)

Since the volume \( V \) is constant and the number of moles of gas \( n \) remains constant, if we increase the pressure \( P \), the temperature \( T \) must also increase.

4. **Effect of Increased Temperature**:
The increase in temperature due to the increased pressure means that the water inside the pressure cooker can reach temperatures higher than 100°C (the normal boiling point of water at atmospheric pressure).

5. **Cooking Time Reduction**:
Higher temperatures allow food to cook faster because the heat energy is more effective in breaking down food materials and facilitating chemical reactions necessary for cooking. This results in a significant reduction in cooking time.

6. **Conclusion**:
Therefore, the reason a pressure cooker reduces cooking time is that the boiling point of water is increased due to the higher pressure, allowing food to cook at higher temperatures.

### Final Answer:
The boiling point of water involved in cooking is increased, which reduces cooking time.

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