If mass-energy equivalence is taken into account , when water is cooled to form ice, the mass of water should :-(Note: The mass energy of an object is the energy equivalent of its mass , as given by `E= mc^(2)`, where m= mass of object & c = speed of light)

Options

A. increase
B. remain unchanged
C. decrease
D. first increase then decrease

Explanation

To solve the question regarding the mass of water when it is cooled to form ice, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Mass-Energy Equivalence**: According to Einstein's equation \( E = mc^2 \), energy (E) is directly proportional to mass (m). This means that any change in energy will result in a change in mass.

2. **Cooling Water**: When water is cooled to form ice, it loses thermal energy. This loss of energy is crucial in determining the change in mass.

3. **Energy Loss**: As the water cools down, it releases energy into the surroundings. This energy loss can be quantified, and it is important to note that the energy is being converted from the internal energy of the water molecules.

4. **Applying the Mass-Energy Relation**: Since energy is being lost from the system (the water), we can say that the total energy of the system decreases. According to the mass-energy equivalence, if energy decreases, the mass must also decrease.

5. **Conclusion**: Therefore, when water is cooled to form ice, the mass of the water decreases due to the loss of thermal energy.

### Final Answer:
The mass of water should **decrease** when it is cooled to form ice.

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