Question

How much heat energy is released when 5g of water at 20°C changes to ice at 0°C? [Specific heat capacity of water = 4.2Jg^-1°C^-1; Specific latent heat of fusion of ice – 336g^-1]

Answer 1

Heat energy released in cooling water to 0°C

= mcθ_f = 5 x 4.2 x 20 = 420J

Heat energy released in freezing water = mL = 5 x 336

= 1680J

∴ Total heat energy released = (1680 + 420)J = 2100J