© Oxford University Press IP1.3.4 Specific latent heat Specific latent heat

© Oxford University Press IP1.3.4 Specific latent heat The amount of energy needed to change the state of 1 kilogram of a substance is called its specific latent heat. You can calculate the amount of energy needed using this equation. energy = specific latent heat  mass JJ/kgkg

© Oxford University Press IP1.3.4 Specific latent heat This table shows the specific latent heat of some materials. Note, the specific latent heat of fusion (for melting a substance) is not the same value as the specific latent heat of vaporisation (for boiling and evaporating a substance).

© Oxford University Press IP1.3.4 Specific latent heat How much energy is required to melt 3 kg of lead? energy needed= specific latent heat of fusion  mass = J/kg  3 kg = J

© Oxford University Press IP1.3.4 Specific latent heat How much energy is required to evaporate 0.5 kg of ethanol? energy needed= specific latent heat of vaporisation  mass = J/kg  0.5 kg = J

© Oxford University Press IP1.3.4 Specific latent heat If kJ are required to melt some ice, what is the mass of that ice? energy needed = specific latent heat of fusion  mass J= J/kg  mass ÷ = mass mass= 0.75 kg

© Oxford University Press IP1.3.4 Specific latent heat If 3390 kJ are required to evaporate some water, what is the mass of that water? energy needed= specific latent heat of vaporisation  mass 3390 kJ= 2260 kJ/kg  mass 3390 ÷ 2260= mass mass= 1.5 kg

© Oxford University Press IP1.3.4 Specific latent heat If it takes J to evaporate 3.75 kg of oxygen, calculate its specific latent heat of vaporisation. energy needed= specific latent heat of vaporisation  mass J= specific latent heat of vaporisation  3.75 kg ÷ 3.75= specific latent heat of vaporisation specific latent heat of vaporisation = 213 J/kg