Topic 14 – Particle model — Edexcel GCSE Physics
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Topic 14 – Particle model explained
This core practical has two parts. For specific heat capacity, learners heat a known mass of water with an electric heater of known power, record temperature against time, and use energy transferred = power × time together with E = mcΔθ to find c.
Read the full explanation
They should insulate the container, stir gently and plot a graph so that a gradient gives the temperature rise per unit time. For melting ice, learners heat crushed ice steadily and record temperature at regular intervals, plotting a temperature-time graph. The temperature stays at 0 °C while ice melts because energy supplied breaks bonds between particles rather than raising temperature; the flat section shows the melting plateau.
Your focus
- Carry out a practical to determine the specific heat capacity of water.
- Obtain and interpret a temperature-time graph for melting ice.
- Explain why temperature remains constant during melting.
Topic 14 – Particle model exam tips
Marking Points
- Measures the mass of water with a balance and records the starting temperature with a thermometer.
- Uses an electric heater of known power and times the heating to calculate energy transferred as power × time.
- Rearranges E = mcΔθ to calculate the specific heat capacity from the energy supplied, mass and temperature rise.
- Plots a temperature-time graph for melting ice and identifies the flat section at 0 °C as the melting plateau.
- Explains that during melting the energy supplied breaks bonds between particles rather than raising temperature.
- Describes precautions such as insulating the container and stirring to reduce unwanted energy transfer and keep temperature uniform.
Examiner Tips
- 💡Show the equation E = mcΔθ, substitute values with units and state the unit of specific heat capacity as J/kg °C.
- 💡Describe the shape of the temperature-time graph, naming the flat section and what it represents.
- 💡Explain sources of error such as energy lost to surroundings and how insulation or a lid reduces them.
Common Mistakes
- Uses the total time rather than the temperature rise in the specific heat capacity calculation; correct this by using the change in temperature Δθ.
- Reads the melting plateau as a rise in temperature; correct this by explaining that temperature stays constant while ice melts.
- Omits insulation or stirring; correct this by adding these to reduce energy loss and keep the water temperature uniform.