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.
More to read
Measure energy during warming
A temperature difference causes energy transfer called heat. A flame can warm water in a beaker, increasing molecular motion and temperature. Without a change of state, calculate the transferred energy using Q = mcΔT. Q is measured in joules; m is mass; c is specific heat capacity; ΔT is the water's final temperature minus its starting temperature. Water has c = 4180 J/kg°C or 4.18 J/g°C. Match the mass unit to c. Measure mass and record temperature against time. The graph's slope shows how quickly temperature rises.
What controls the energy needed?
More mass or a larger temperature rise requires more energy. The material matters too: specific heat capacity gives the energy needed per kilogram for each degree of warming. Water has c = 4180 J/kg°C; copper has c = 385 J/kg°C.
Measure temperature once a minute during heating. A straight temperature-time line indicates a steady warming rate. A changing slope may reflect heat losses. During a change of state, temperature may stay constant despite continued heating.
Track heat exchanged between materials
Heat moves from warmer material to cooler material. Mix hot water with cold water. If surroundings and the container absorb negligible energy, Q_lost = Q_gained, so m_hot c ΔT_hot = m_cold c ΔT_cold. Use positive temperature-drop and temperature-rise magnitudes. Solve for an unknown mass or temperature. Insulation and a lid limit heat exchange with the surroundings; stirring spreads warmth evenly. A metal's specific heat can also be measured by placing hot metal in water and measuring the temperature change.
Find heating power from temperature data
Internal energy combines particles' microscopic kinetic and potential energies. Temperature relates to average particle kinetic energy; heat describes energy being transferred. Raising 100 g of water from 20 °C to 30 °C requires Q = 100 × 4.18 × 10 = 4180 J. With a thermometer and stopwatch, measure temperature at 30-second intervals. Graph temperature against time. Multiply its slope in °C/s by mass and specific heat capacity to find net heating power in watts.
Keeping it Hot (or Cold): The Science of Insulation
Students test different materials to see which best slows heat transfer. They wrap beakers of hot water in foil cotton wool bubble wrap and measure temperature drop over time. The material with the smallest temperature drop is the best insulator. This connects to Q = mcΔT. Less temperature change means less heat lost. They learn to identify sources of error like convection currents in the water or radiation from the surface. Repeating measurements improves reliability.
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