Density of `H_(2)O` is maximum at :

Options

A. `0^(@)C`
B. `100^(@)C`
C. `-273^(@)C`
D. `4^(@)C`

Answer

To determine at what temperature the density of water (H₂O) is maximum, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Density**:
Density is defined as mass per unit volume (Density = Mass/Volume). For a given mass of water, if the volume decreases, the density will increase.

2. **Behavior of Water with Temperature**:
Water behaves uniquely as it cools. As the temperature decreases from room temperature (around 25°C) to 0°C, the volume of water decreases, and thus its density increases.

3. **Hydrogen Bonding in Water**:
Water molecules are held together by strong intermolecular hydrogen bonds. As water cools, these hydrogen bonds become more pronounced, leading to a decrease in volume.

4. **Critical Temperature - 4°C**:
When water is cooled to around 4°C, it reaches a point where the hydrogen bonds are optimally formed, resulting in the maximum density. Below this temperature, the structure of water begins to change as it approaches freezing (0°C), leading to an increase in volume due to the formation of a crystalline structure (ice), which is less dense than liquid water.

5. **Conclusion**:
Therefore, the density of water is maximum at 4°C. This is the temperature at which water has the highest density before it starts to expand again as it freezes.

### Final Answer:
The density of H₂O is maximum at **4°C**.

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