The energy transferred from the water in the kettle to its surroundings in 2 hours is 46 200 J. The mass of water in the kettle is 0.50 kg. The specific heat capacity of water is 4200 J/kg °C. What is its temperature after 2 hours?
The water loses 4200 J/kg °C * 0.5 kg = 2100 J/°C
As it's lost 46,200 J in total (regardless of the time it took for this to happen), it must have reduced in temperature by 46,200 J / 2100 J/°C = 22°C.
Assuming 100°C initially, temperature of water in kettle is now 78°C.
DB
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