What a learner can do afterwards
- Uses a thermometer and stopwatch to record temperature change over time in a heating experiment
- Applies Q = mcΔT to calculate the energy transferred to a substance being heated
- Identifies sources of energy loss in a heating experiment (e.g. heat to surroundings) and suggests improvements
- Plots a temperature-time graph and identifies the temperature rise rate from its gradient
1 · Read
In a heating experiment, you measure how hot something gets as you add energy to it. You need a thermometer to read the temperature, and a stopwatch to time how long you have been heating. The energy transferred follows a tidy rule: Q = mcΔT. Here Q is the energy in joules, m is the mass in kilograms, ΔT is the temperature change, and c is the specific heat capacity.
The specific heat capacity, c, tells you how much energy it takes to heat 1 kg of a material by 1°C. It is a property of the material itself, and you look it up in a table. Water has one of the largest values of any common substance, about 4200 J/kg°C, so water soaks up a lot of energy before its temperature climbs much. That is one reason the sea warms up and cools down so slowly.
Say you heat 0.2 kg of water and its temperature rises from 20°C to 40°C. Water has a specific heat capacity of 4200 J/kg°C, so ΔT = 20°C. Using Q = mcΔT: Q = 0.2 x 4200 x 20 = 16,800 J of energy transferred.
Not all your energy heats the water. Some escapes into the air, the beaker, or the surroundings, so the energy you work out from Q = mcΔT is usually less than the energy you supplied. You can cut this loss by using a lid, wrapping the beaker in insulation, or timing your heating carefully.
Plotting temperature against time turns your readings into a picture. The steepness of the line, its gradient, tells you how fast the temperature rose. If the temperature climbs steadily from 15°C to 45°C in 6 minutes, the gradient is 30 ÷ 6 = 5°C per minute. A steeper line means the water warmed faster.
Record temperature over time, use Q = mcΔT to work out the energy transferred, read the rise rate from the gradient of your graph, and watch out for heat lost to the surroundings.
Adapted from OpenStax College Physics (CC-BY 4.0), openstax.org · license
The rewritten readings were written for this dataset.
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