To determine the heat required, let's consider two stages: raising the temperature of water from 20°C to 100°C, and converting water at 100°C to steam. We'll calculate each part separately and sum them to find the total heat required.
Phase 1: Heating water from 20°C to 100°C
The formula for heat required is given by Q = m × c × ΔT, where:
- m is the mass of the water (2 kg)
- c is the specific heat capacity of water (4.2 kJ kg-1 K-1)
- ΔT is the change in temperature, which is 100°C - 20°C = 80°C
Substituting the values, Q1 = 2 × 4.2 × 80 = 672 kJ
Phase 2: Converting water at 100°C to steam
The heat required for the phase change is calculated using Q = m × L, where:
- L is the latent heat of steam (2256 kJ kg-1)
Thus, Q2 = 2 × 2256 = 4512 kJ
Total Heat Required
Adding the heat from both phases, we have Qtotal = Q1 + Q2 = 672 + 4512 = 5184 kJ
The computed heat required is 5184 kJ.