Heat energy: WAEC Physics Past Questions and Answers

What the WAEC syllabus covers in Heat energy

Our summary: Temperature, expansion, heat transfer, gas laws, heat capacity, latent heat, vapour and humidity.

• Temperature and its measurement (Concept of temperature as degree of hotness or coldness of a body. Construction and graduation of a simple thermometer. Properties of thermometric liquids. The following thermometers should be treated: constant-volume gas thermometer, resistance thermometer, thermocouple, liquid-in-glass thermometer including maximum and minimum thermometer and clinical thermometer; pyrometer should be mentioned. Celsius and absolute scales of temperature. Kelvin and degree Celsius as units of temperature.)
• Effects of heat on matter: rise in temperature, change of phase (state), expansion, change of resistance (Use of the kinetic theory to explain effects of heat. Mention should be made of the following effects: change of colour, thermionic emission, change in chemical properties.)
• Thermal expansion - linear, area and volume expansivities (Qualitative and quantitative treatment. Consequences and application of expansions: expansion in buildings and bridges, bimetallic strips, thermostat, over-head cables causing sagging and in railway lines causing buckling. Real and apparent expansion of liquids. Anomalous expansion of water. Per kelvin (K⁻¹) as the unit of expansivity.)
• Heat transfer - conduction, convection and radiation (Use of the kinetic theory to explain the modes of heat transfer. Simple experimental illustrations. Treatment should include the explanation of land and sea breezes, ventilation and applications in cooling devices. The vacuum flask.)
• The gas laws - Boyle's law, Charles' law, pressure law and general gas law (The laws should be verified using simple apparatus. Use of the kinetic theory to explain the laws. Simple problems may be set. Mention should be made of the operation of safety air bags in vehicles.)
• Measurement of heat energy: concept of heat capacity and specific heat capacity (Use of the method of mixtures and the electrical method to determine the specific heat capacities of solids and liquids. Land and sea breezes related to the specific heat capacity of water and land. J kg⁻¹ K⁻¹ as unit of specific heat capacity.)
• Latent heat: concept of latent heat (Explanation and types of latent heat.)
• Latent heat: melting point and boiling point (Determination of the melting point of solid and the boiling point of a liquid. Effects of impurities and pressure on melting and boiling points. Application in pressure cooker.)
• Latent heat: specific latent heat of fusion and of vaporization (Use of the method of mixtures and the electrical method to determine the specific latent heats of fusion of ice and of vaporization of steam. Applications in refrigerators and air conditioners. J kg⁻¹ as unit of specific latent heat.)
• Evaporation and boiling (Effect of temperature, humidity, surface area and draught on evaporation to be discussed.)
• Vapour and vapour pressure (Explanation of vapour and vapour pressure. Demonstration of vapour pressure using simple experiments. Saturated vapour pressure and its relation to boiling.)
• Humidity, relative humidity and dew point (Measurement of dew point and relative humidity. Estimation of humidity of the atmosphere using wet and dry-bulb hygrometer.)
• Humidity and the weather (Formation of dew, fog and rain.)

Syllabus content © The West African Examinations Council (WASSCE (harmonised West African syllabus)).