AQA Combined Science (8464) 6.1.1.3 · Quantitative
Energy changes in systems
Combined Science · Foundation tier
Start here
You heat the same mass of water and of aluminium with the same heater.
If you had to guess, which one warms up faster?
Key words
- specific heat capacity
- thermal energy
- temperature change
Key knowledge
The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.
change in thermal energy = mass × specific heat capacity × temperature change
ΔE = m c Δθ
- change in thermal energy, ΔE, in joules (J)
- mass, m, in kilograms (kg)
- specific heat capacity, c, in joules per kilogram per degree Celsius (J/kg °C)
- temperature change, Δθ, in degrees Celsius (°C)
This equation is on the equation sheet.
- Measure the mass of the block.
- Put a heater and a thermometer in the block and wrap it in insulation.
- Record the starting temperature.
- Switch on the heater. Measure the energy transferred with a joulemeter, or use power × time.
- Record the final temperature and work out the temperature change.
- Use c = ΔE ÷ (m × Δθ) to find the specific heat capacity.
Some energy is dissipated to the surroundings. This makes the measured value higher than the true value. Insulating the block reduces this.
Wrong: Using the final temperature as Δθ.
Right: Δθ is final temperature minus starting temperature.
Wrong: Putting a mass in grams into the equation.
Right: Convert to kilograms first. Divide by 1000.
Key fact
The specific heat capacity of a substance is the energy required to raise the temperature of 1 kg of it by 1 °C. Change in thermal energy = mass × specific heat capacity × temperature change.
Water has a high specific heat capacity of 4200 J/kg °C.
Each kilogram carries a lot of energy for each degree it cools.
- Calculate: work out a number and show each line.
- Describe: give the steps of a method in order.
- Explain: say what happens and why.
Previous and next
Connects to
Ask MrBadmus
Not sure about something in this lesson?