Density of water is maximum

Options

A. at `0^(@)C`
B. at `4^(@)C`
C. above `4^(@)C`
D. below `4^(@)C`

Explanation

### Step-by-Step Solution

1. **Understanding the Question**: The question asks about the temperature at which the density of water is maximum.

2. **Identifying the Temperature**: The density of water is maximum at **4 degrees Celsius**.

3. **Explaining the Reason**:
- As the temperature of water increases from **0 to 4 degrees Celsius**, some hydrogen bonds between water molecules break.
- This breaking of hydrogen bonds allows the water molecules to come closer together.

4. **Effect on Density**:
- When the water molecules come closer together, the **volume of the water decreases**.
- Since density is defined as mass per unit volume (Density = Mass/Volume), a decrease in volume while mass remains constant leads to an **increase in density**.

5. **Behavior Above 4 Degrees Celsius**:
- When the temperature rises above **4 degrees Celsius**, the kinetic energy of the water molecules increases.
- This increase in kinetic energy causes the water molecules to move apart, leading to an **increase in volume**.

6. **Final Effect on Density**:
- As the volume increases above 4 degrees Celsius, the density of water **decreases** because the mass remains constant while the volume increases.

7. **Conclusion**: Therefore, the maximum density of water occurs at **4 degrees Celsius** due to the combined effects of hydrogen bond breaking and the behavior of molecules with temperature changes.