Core Practical: Investigating Specific Heat Capacity (Edexcel GCSE Physics)

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Core Practical 6: Investigating Specific Heat Capacity

Equipment List

Practical SHC Equipment list, downloadable IGCSE & GCSE Physics revision notes

  • Resolution of measuring equipment:
    • Thermometer = 0.1 °C
    • Voltmeter = 0.1 V
    • Ammeter = 0.1 A
    • Stopwatch = 1 s
    • Digital balance = 1 g

Experiment 1: Determining the Specific Heat Capacity of Water

Aim of the Experiment

  • The aim of this experiment is to determine the specific heat capacity of water by measuring the energy required to increase the temperature of a known amount by 1°C

Method

Practical SHC Diagram of setup, downloadable IGCSE & GCSE Physics revision notes

Apparatus for heating water and measuring energy supplied

  1. Place the beaker on the digital balance and press 'tare'
  2. Add approximately 250 ml of water and record the mass of the water
  3. Place the immersion heater and thermometer in the water
  4. Connect up the circuit as shown in the diagram, with the ammeter in series with the power supply and immersion heater, and the voltmeter in parallel with immersion heater
  5. Record the initial temperature of the water at time 0 s
  6. Turn on the power supply, set at approximately 10 V, and start the stopwatch
  7. Record the voltage and current
  8. Continue to record the temperature, voltage and current every 60 seconds for 10 minutes

  • An example of a results table might look like this:

Practical SHC Results table 1, downloadable IGCSE & GCSE Physics revision notesPractical SHC Results table 2, downloadable IGCSE & GCSE Physics revision notes

Analysis of Results

  • Calculate the energy supplied each minute using the formula:

    Electrical energy (J) = voltage (V) × current (A) × time (s)

  • Calculate the temperature change by subtracting the temperature at time 0 s from the temperature recorded each minute
  • Calculate the average mass of the water by adding the mass at the start and the mass at the end and then dividing the total by two
  • Plot a graph of the energy supplied (y-axis) against the temperature change multiplied by the average mass (x-axis)
  • The gradient of this graph will be the specific heat capacity of the water
  • Take the gradient in the straight-line region of the graph:
    • Divide the change on the y-axis between two points on the straight line region, with the change on the x-axis between the same two points

Practical SHC Taking gradient, downloadable IGCSE & GCSE Physics revision notes

The gradient of the graph is equal to the specific heat capacity of the water, assuming a perfectly efficient immersion heater

Experiment 2: Obtaining a Temperature-Time Graph for Melting Ice

Aim of the Experiment

  • The aim of this experiment is to plot a graph of the temperature of ice, against time, as it is heated to water

Method

Change of State Apparatus, downloadable IGCSE & GCSE Physics revision notes

Apparatus used to heat ice and measure its temperature as it melts

  1. Place some ice in a beaker so it is about half-full
  2. Place a thermometer in the beaker
  3. Place the beaker on a tripod and gauze and slowly start to heat it using a bunsen burner
  4. As the beaker is heated, take regular temperature measurements (e.g. at one minute intervals)
  5. Continue this whilst the substance changes state (from solid to liquid)
  6. The results can then be plotted on a graph

Practical SHC Heating curve, downloadable IGCSE & GCSE Physics revision notes

A heating curve will show a flat section whilst the ice is melting

Evaluating the Experiments

Systematic Errors:

  • Ensure the digital balance is set to zero before taking measurements of mass
  • It may be necessary to determine the efficiency of the immersion heater before experiment 1:
    • The specific heat capacity of water has a known value of 4200 J/kg/°C
    • If the efficiency of the heater is less than 1 then the values obtained for specific heat capacity will be larger than expected

  • Remember to only take gradients on the straight-line region
    • Before this point the energy supplied is being used to heat the immersion heater itself

Random Errors:
  • Stir the ice water constantly whilst heating in experiment 2
  • When the current or voltage values appear to be changing between two values next to one another then be consistent in choosing the higher value

Safety Considerations

  • The immersion heater will get very hot
    • Make sure not to touch it, and have a heatproof mat ready to place it on

  • Make sure that the immersion heater is connected to a direct current supply
  • The beaker may become unstable with an immersion heater and thermometer resting in it
    • If you feel this is the case then use a clamp stand to hold both

  • Wear goggle while heating water
  • Make sure to stand up during the whole experiment, to react quickly to any spills

Examiner Tip

Although there is a lot of detail here, if you can begin any questions about this experiment by writing down the equation for specific heat capacity then you will have given yourself some clues about how best to proceedTaking a gradient is a more reliable way of determining an answer than just using a single value, so take time to understand the process of plotting graphs and using their gradients to make conclusions

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Ashika

Author: Ashika

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Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.