A kettle heats 1.5 kg of water from 20 °C to 100 °C. The specific heat capacity of water is 4200 J/(kg °C). Calculate the energy required in kilojoules.

Thermodynamics Challenge #1 — Specific Heat

Heating
a kettle.

Thermodynamics Easy

Problem

A kettle heats 1.5 kg of water from 20 °C to the boiling point at 100 °C. The specific heat capacity of water is \( c = 4200\ \mathrm{J/(kg\,^{\circ}C)} \). Calculate the energy required, in kilojoules.

Mass of water\( m = 1.5\ \mathrm{kg} \)
Temperature rise\( 20 \to 100\ ^{\circ}\mathrm{C} \)
Specific heat\( c = 4200\ \mathrm{J/(kg\,^{\circ}C)} \)
Answer inkilojoules

Ignore heat lost to the kettle itself and to the surroundings.

Hint: the energy needed is \( Q = m c \Delta T \). How many degrees does the water actually rise by — and what does the question want the answer in?

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