A beaker contains a liquid solvent at room temperature. An electric heater immersed in the solvent is switched on, supplying thermal energy. The temperature of the liquid increases until it reaches its boiling point, at which point it begins to turn into a gas.
Describe, in terms of molecules and their motion, how a liquid differs from a gas.
Describe what happens to the molecules of the liquid as its temperature begins to increase.
Explain, in terms of intermolecular forces, why a supply of thermal energy is needed to change the liquid into a gas at its boiling point.
The density of the solvent is 0.80 g/cm30.80 \text{ g/cm}^30.80 g/cm3. The volume of the solvent in the beaker is 75 cm375 \text{ cm}^375 cm3.
The liquid is heated to its boiling point. It then absorbs 51 000 J51\,000 \text{ J}51000 J of thermal energy, causing all of the liquid to change into a gas.
Calculate the specific latent heat of vaporisation of this solvent.
528 exam-style questions on CIE IGCSE Physics 2.2 Thermal properties and temperature, covering 2.2.1 Thermal expansion of solids, liquids and gases, 2.2.2a Internal energy and temperature, 2.2.2b Specific heat capacity, 2.2.3a Melting, boiling, condensation and solidification, 2.2.3b Evaporation, and 2.2.3c Cooling by evaporation. Each one has a worked solution and a mark scheme showing where the marks go.