What is the value of specific heat of water in SI unit? Does it very with temperature?

Answer

### Step-by-Step Solution:

1. **Understanding Specific Heat**:
Specific heat is defined as the amount of heat required to change the temperature of a unit mass of a substance by one degree Celsius (or one Kelvin).

2. **Specific Heat of Water**:
The specific heat of water is a well-known value. In SI units, it is expressed as:
\[ S_W = 4180 \, \text{J/kg} \cdot \text{K} \]
This means that it takes 4180 joules of energy to raise the temperature of 1 kilogram of water by 1 Kelvin (or 1 degree Celsius).

3. **Does Specific Heat Vary with Temperature?**:
Yes, the specific heat of water does vary with temperature, but this variation is relatively small over a limited temperature range.

4. **Reason for Variation**:
As the temperature of water increases, the vibrational energy of the water molecules also increases. This means that more energy is required to achieve the same temperature change because the molecules are already in a higher energy state.

5. **Conclusion**:
Therefore, while the specific heat of water is approximately 4180 J/kg·K, it can change slightly with temperature due to the increase in vibrational energy of the molecules.