Define specific latent heat of fusion.
A test-tube contains 50 g50\text{ g}50 g of liquid naphthalene at its melting temperature of 80∘C80^\circ\text{C}80∘C. An identical test-tube contains 50 g50\text{ g}50 g of a mixture of solid and liquid naphthalene at a temperature of 80∘C80^\circ\text{C}80∘C.
Both test-tubes are placed in a water bath maintained at a constant temperature of 95∘C95^\circ\text{C}95∘C.
State and explain which test-tube contains naphthalene with the lower temperature after 5 minutes.
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When hand sanitizer containing alcohol is applied to a person's skin, it evaporates rapidly.
Explain, in terms of molecules, how the evaporation of alcohol cools the skin.
Explain why this cooling process is more effective if the person waves their hand.
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.