4.3.2.3

4.3.2.3 Changes of heat and specific latent heat

E=mL

4.3.2.3 Changes of heat and specific latent heat

Content

If a change of state happens:

The energy needed for a substance to change state is called latent heat. When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.

The specific latent heat of a substance is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.

energy for a change of state = mass × specific latent heat

E =mL

energy, E, in joules, J

mass, m, in kilograms, kg

specific latent heat, L, in joules per kilogram, J/kg

Specific latent heat of fusion – change of state from solid to liquid Specific latent heat of vaporisation – change of state from liquid to vapour

Students should be able to interpret heating and cooling graphs that include changes of state.

Students should be able to distinguish between specific heat capacity and specific latent heat.

MS 1c - Use ratios, fractions and percentages

MS 3b Change the subject of an equation

MS 3c Substitute numerical values into algebraic equations using appropriate units for physical quantities

MS 3d -Substitute numerical values into algebraic equations using appropriate units for physical quantities


AT5 Safe use of appropriate apparatus in a range of contexts to measure energy changes/ transfers and associated values such as work done (links to A-level AT a, b).


Resources

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Practicals

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