Required Practical: Investigating Specific Heat Capacity (AQA GCSE Physics)

Revision Note

Test yourself
Leander

Author

Leander

Last updated

Required Practical 1: Investigating Specific Heat Capacity

Aims of the Experiment

  • The aim of the experiment is to determine the specific heat capacity of a substance, by linking the amount of energy transferred to the substance with the rise in temperature of the substance

Variables:

  • Independent variable = Time, t
  • Dependent variable = Temperature, θ
  • Control variables:
    • Material of the block
    • Current supplied, I
    • Potential difference supplied, V

Equipment List

Heat Capacity Apparatus Table, downloadable AS & A Level Physics revision notes

  • Resolution of measuring equipment:
    • Thermometer = 1 °C
    • Stopwatch = 0.01 s
    • Voltmeter = 0.1 V
    • Ammeter = 0.01 A

Method

Specific Heat Capacity Apparatus, downloadable AS & A Level Physics revision notes

Apparatus to investigate the specific heat capacity of the aluminium block

  1. Start by assembling the apparatus, placing the heater into the top of the block
  2. Measure the initial temperature of the aluminium block from the thermometer
  3. Turn on the power supply and start the stopwatch
  4. Whilst the power supply is on, the heater will heat up the block. Take several periodic measurements, eg. every 1 minute of the voltage and current from the voltmeter and ammeter respectively, calculating an average for each at the end of the experiment up to 10 minutes
  5. Switch off the power supply, stop the stopwatch and leave the apparatus for about a minute. The temperature will still rise before it cools
  6. Monitor the thermometer and record the final temperature reached for the block

  • An example table of results might look like this:

Specific Heat Capacity Example Table, downloadable AS & A Level Physics revision notes

Analysis of Results

  • The thermal energy supplied to the block can be calculated using the equations:

E space equals space Q V and Q space equals space I t

  • Where:
    • E = thermal energy, in joules (J)
    • Q = Charge, in coulombs (C)
    • I = current, in amperes (A)
    • V = potential difference, in volts (V)
    • t = time, in seconds (s)

  • Combining the equations:
    • Rearrange to make Q the subject

E space equals space Q V space space rightwards double arrow space space Q space equals fraction numerator space E over denominator V end fraction

    • Substitute into the Q = It equation

Q space equals space I t space space

fraction numerator E over denominator V space end fraction space equals space I t

    • Rearrange to make E the subject

E space equals space I V t

 

  • The change in thermal energy is defined by the equation:

increment E space equals space m c increment theta

  • Where:
    • ΔE = change in energy, in joules (J)
    • m = mass, in kilograms (kg)
    • c = specific heat capacity, in joules per kilogram per degree Celsius (J/kg °C)
    • Δθ = change in temperature, in degrees Celsius (°C)

  • Rearranging for the specific heat capacity, c:

c space equals space fraction numerator increment E over denominator m increment theta end fraction

  • To calculate Δθ:

increment theta space equals space theta subscript f space minus space theta subscript i

  • Where:
    • theta subscript f = final temperature
    • theta subscript i = initial temperature

  • To calculate ΔE:

increment E space equals space I V theta subscript f space minus space I V theta subscript i

  • Where:
    • I = average current, in amperes (A)
    • V = average potential difference (V)
    • θf = final time, in seconds (s)
    • θi = initial time, in seconds (s)

  • These values are then substituted into the specific heat capacity equation to calculate the specific heat capacity of the aluminium block

Evaluating the Experiment

Systematic Errors:

  • Make sure the voltmeter and ammeter are initially set to zero, to avoid zero error

Random Errors:

  • Not all the energy transferred from the heater will be transferred to the block, some will be dissipated to the surroundings into the surroundings and some will be transferred to the thermometer (also part of the surroundings) 
    • This means the measured value of the specific heat capacity is likely to be higher than what it actually is
    • To reduce this effect, make sure the block is fully insulated

  • A joulemeter could be used to calculate energy directly
    • This would eliminate errors from the voltmeter, ammeter and the stopwatch

  • Make sure the temperature value is read at eye level from the thermometer, to avoid parallax error
  • The experiment can also be repeated with a beaker of water of equal mass, the water should heat up slower than the aluminium block

Safety Considerations

  • Make sure never to touch the heater whilst it is on, otherwise, it could burn skin or set something on fire
    • Run any burns immediately under cold running water for at least 5 minutes

  • Allow time for all the equipment, including the heater, wire and block to cool before packing away the equipment
  • Keep water away from all electrical equipment
  • Wear eye protection if using a beaker of hot water

Examiner Tip

This practical investigation is usually done as a teacher demonstration because of the specialist equipment used. Therefore, students often find it more difficult to engage with than a hands-on practical, and so they can often find it quite confusing. This Required Practical does come up in exams very frequently, so you do need to make the extra effort to understand the equipment, the set-up, and how the measurements are taken.

The main idea is that the measurements of current and potential difference allow you to calculate the energy transferred to the metal block, and from there you can use the change in temperature and the energy supplied to calculate the specific heat capacity of the metal.

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Leander

Author: Leander

Expertise: Physics

Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.