How is heavy water prepared? Compare its physical properties with those of ordinary water.

Explanation

### Step-by-Step Solution

**Step 1: Preparation of Heavy Water**
Heavy water (D2O) can be prepared through the process of exhaustive electrolysis of ordinary water (H2O). During this process, hydrogen and oxygen gases are produced, and the heavier isotope of hydrogen, deuterium, becomes concentrated in the remaining water.

**Step 2: Comparison of Physical Properties**
To compare the physical properties of heavy water (D2O) and ordinary water (H2O), we will look at several key properties: molecular mass, melting point, boiling point, density, and enthalpy of vaporization.

1. **Molecular Mass:**
- Ordinary Water (H2O): 18.015 g/mol
- Heavy Water (D2O): 20.027 g/mol

2. **Melting Point:**
- Ordinary Water (H2O): 273 K
- Heavy Water (D2O): 276.8 K

3. **Boiling Point:**
- Ordinary Water (H2O): 373 K
- Heavy Water (D2O): 374.4 K

4. **Density (at 298 K):**
- Ordinary Water (H2O): 1 g/cm³
- Heavy Water (D2O): 1.1059 g/cm³

5. **Enthalpy of Vaporization:**
- Ordinary Water (H2O): 40.66 kJ/mol
- Heavy Water (D2O): 41.66 kJ/mol

### Summary of Comparison
- Heavy water has a higher molecular mass, melting point, boiling point, density, and enthalpy of vaporization compared to ordinary water.