AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Temperature change, ∆θ, in degrees Celsius, °C.
Full specification wording
Temperature changes in a system and specific heat capacity: temperature change, ∆θ, in degrees Celsius, °C.
Temperature change, ∆θ, is the difference between the final and initial temperatures of a system, measured in degrees Celsius, °C. It is calculated as ∆θ = θ_final − θ_initial, so a rise gives a…
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 9 of 10
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Temperature change, ∆θ, is the difference between the final and initial temperatures of a system, measured in degrees Celsius, °C. It is calculated as ∆θ = θ_final − θ_initial, so a rise gives a positive value and a fall gives a negative value. In the equation E = mc∆θ, ∆θ must match the energy transfer: heating gives a positive ∆θ, while cooling releases energy and gives a negative ∆θ.
For example: Water heated from 20 °C to 65 °C has ∆θ = 45 °C. Because a change of 1 °C equals a change of 1 K, the same numerical value can be used in kelvin when calculating energy, but the symbol and unit must remain consistent with the question.
What earns the marks
- Define temperature change as final temperature minus initial temperature, ∆θ = θ_final − θ_initial.
- Calculate ∆θ correctly from thermometer readings, including cases where the temperature falls.
- Use ∆θ in the equation E = mc∆θ with the correct sign to show whether energy is transferred to or from the system.
- Recognise that a temperature change of 1 °C is numerically equal to a temperature change of 1 K.
- Keep the unit °C for ∆θ when the question uses degrees Celsius, and avoid confusing temperature change with absolute temperature.
- Check that the calculated ∆θ is consistent with the direction of heating or cooling described in the question.
Common mistakes and how to put them right
Adding the initial and final temperatures instead of subtracting.
Put it right by using ∆θ = θ_final − θ_initial.
Using the final temperature as ∆θ.
Put it right by subtracting the initial temperature first.
Mixing kelvin and degrees Celsius within one calculation without converting.
Put it right by using a consistent temperature scale throughout.
Exam tips
- Underline the initial and final temperatures in the question before calculating ∆θ.
- Show the subtraction explicitly so the examiner can see how the temperature change was obtained.
- If a temperature falls, state that ∆θ is negative and explain that energy is transferred away from the system.
Try the lesson
The start of the Temperature changes in a system and specific heat capacity: temperature change, ∆θ, in degrees Celsius, °C. lesson, made from checked teaching notes for this specification point.
Have a go first
A beaker of water is heated from 18 °C to 47 °C. What is the temperature change, ∆θ, of the water?
Listen
Temperature change, ∆θ, is the difference between the final and initial temperatures of a system, measured in degrees Celsius, °C. It is calculated as ∆θ = θ_final − θ_initial, so a rise gives a positive value and a fall gives a negative value. In the equation E = mc∆θ, ∆θ must match the energy transfer: heating gives a positive ∆θ, while cooling releases energy and gives a negative ∆θ. For example, water heated from 20 °C to 65 °C has ∆θ = 45 °C. Because a change of 1 °C equals a change of 1 K, the same numerical value can be used in kelvin when calculating energy, but the symbol and unit must remain consistent with the question. A strong answer earns marks for these points. Define temperature change as final temperature minus initial temperature, ∆θ = θ_final − θ_initial. Calculate ∆θ correctly from thermometer readings, including cases where the temperature falls. Use ∆θ in the equation E = mc∆θ with the correct sign to show whether energy is transferred to or from the system. Recognise that a temperature change of 1 °C is numerically equal to a temperature change of 1 K. A common slip: Adding the initial and final temperatures instead of subtracting. Instead, using ∆θ = θ_final − θ_initial. Exam tip: Underline the initial and final temperatures in the question before calculating ∆θ.
See it
Key words
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Temperature change
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Sign conventions in calculations
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Units and consistency
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See every definition
- Temperature change
- The difference between the final and initial temperatures of a system, calculated as ∆θ = θ_final − θ_initial and measured in degrees Celsius, °C.
- Sign conventions in calculations
- A rise in temperature gives a positive value and a fall gives a negative value, so heating gives a positive ∆θ while cooling releases energy and gives a negative ∆θ.
- Units and consistency
- The symbol and unit must remain consistent with the question, and a change of 1 °C equals a change of 1 K so the same numerical value can be used in kelvin.
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