National 5PhysicsSQARevision NotesProperties Of MatterSpecific Heat CapacityCalculating Specific Heat Capacity

Calculating Specific Heat Capacity (SQA National 5 Physics): Revision Note

Exam code: X857 75

Leander Oates

Written by: Leander Oates

Reviewed by: Caroline Carroll

Updated on

Calculating specific heat capacity

  • The specific heat capacity, c, of a substance is defined as:

The amount of heat energy required to raise the temperature of 1 kg of the substance by 1 °C per kilogram of mass (J kg-1 °C-1)

  • The specific heat capacity of a substance can be calculated using the relationship:

heat space energy space space equals space specific space heat space capacity space space cross times space mass space cross times space change space in space temperature

E subscript h space equals space c m straight capital delta T

  • Where:

    • E subscript h = change in heat energy, in joules (straight J)

    • c= specific heat capacity, in joules per kilogram per degree Celsius (straight J space kg to the power of negative 1 end exponent space degree straight C to the power of negative 1 end exponent)

    • m = mass, in kilograms (kg)

    • increment T = change in temperature, in degrees Celsius (°C)

  • The amount of heat energy required to change the temperature of a substance is directly proportional to:

    • Temperature change, E subscript h space proportional to space increment T

    • Mass, E subscript h space proportional to space m

    • Specific heat capacity of the material, E subscript h space proportional to space c

  • When two quantities are directly proportional to one another, it means that:

    • Increasing one will increase the other by the same factor, and vice versa

      • Doubling once quantity will double the other

      • Halving one quantity will halve the other

Worked Example

Water of mass 0.48 space kg is increased in temperature by 0.70 space degree straight C. The specific heat capacity of water is 4180 space straight J space kg to the power of negative 1 end exponent space degree straight C to the power of negative 1 end exponent .

Calculate the amount of heat energy transferred to the water.

 

Answer:

Step 1: Write down the known quantities

  • Mass, m space equals space 0.48 space kg

  • Change in temperature, increment T space equals space 0.70 space degree straight C

  • Specific heat capacity, c space equals space 4180 space straight J space kg to the power of negative 1 end exponent space degree straight C to the power of negative 1 end exponent

Step 2: Write down the relevant relationship

E subscript h space equals space c m straight capital delta T

Step 3: Calculate the heat energy transferred by substituting in the values

E subscript h space equals space left parenthesis 4180 right parenthesis space cross times space left parenthesis 0.48 right parenthesis space cross times space left parenthesis 0.7 right parenthesis space equals space 1404.48

Step 4: Round the answer to 2 significant figures

  • The least precise data point is 2 s.f.

  • Therefore, the calculated value can only be given to the same precision

E subscript h space equals space 1400 space straight J space open parentheses 2 space straight s. straight f. close parentheses

Examiner Tips and Tricks

The specific heat capacity relationship will be given on your relationships sheet, so don't worry if you cannot remember it, but it is important that you understand how to use it. You will also be given the specific heat capacity of a substance in your data sheet, so you do not need to memorise any values.

Always remember to round your final answer to the correct number of significant figures, and to provide the unit. Students often lose marks in the exam for not doing so.

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    Author
    Reviewer
    Leander Oates

    Author: Leander Oates

    Expertise: Physics Content Creator

    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.

    Caroline Carroll

    Reviewer: Caroline Carroll

    Expertise: Physics & Chemistry Subject Lead

    Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.