Melt 500 g of ice at 0°C to water at 0°C. Given Lf = 3.36×10⁵ J kg⁻¹, find the heat required.

Solution & explanation

1. Given: m = 500 g; Lf = 3.36×10⁵ J kg⁻¹.

2. Convert grams to kilograms.

   $$m=\frac{500}{1000}=0.5$$

3. Temperature is unchanged, so use latent heat, not mcΔT.

   $$Q=L_f\times m$$

4. Substitute.

   $$Q=0.5\times 3.36\times {10}^5$$

5. Take half of 336000.

   $$Q=168000$$

6. Convert to kJ.

   $$Q_{\mathrm{kJ}}=\frac{168000}{1000}=168$$

7. State the result with units: 168 kJ absorbed.

Q = 168 kJ