Heating changes the energy stored within the Aiming for Grade 8 LOs: ice cubes that have food colouring in them. Ask the students to system by increasing the energy of the particles describe the processes taking place. Use the concepts of kinetic and that make up the system. This either raises the potential energy to explain changes in Main temperature of the system or produces a change internal energy. of state. Internal energy (20 min) Begin heating the beaker of iced water Describe the changes in the size of and discuss the energy transfers involved. Initially there will be no intermolecular forces during changes of 3.2.2 If the temperature of the system increases, temperature increase, allowing discussion of the latent heat and state. the increase in temperature depends on the the repositioning of the bonds of the particles. mass of the substance heated, the type of As the ice melts and the temperature starts to increase, begin to material, and the energy input to the system. describe the changes in motion for the particles. By the time the The following equation applies: water is boiling, the students should have a good understanding change in thermal energy of internal energy. = mass × specific heat capacity × temperature change Particle behaviour (20 min) Describe the behaviour of the [Δ E = m c ] Δθ particles in a solid, liquid, and gas with a focus on the forces change in thermal energy E in joules, J Δ between the particles. Describe the attraction between individual mass m in kilograms, kg particles and how the motion changes. Additional details about the specific heat capacity c in joules per kilogram behaviour of gases will be covered in the next few lessons. per degree Celsius, J/kg °C temperature change in degrees Celsius, °C. Δθ Plenaries The specific heat capacity of a substance is the Convection revisited (10 min) Repeat the second starter, but amount of energy required to raise the ask the students to describe the changes in particle behaviour for temperature of one kilogram of the substance by the ice. one degree Celsius. (5 min) Can the students describe forces are What forces? responsible for attraction and repulsion between molecules and
Heating changes the energy stored within the system by increasing the energy of the particles that make up the system. This either raises the temperature of the system or produces a change of state. 3.2.2 If the temperature of the system increases, the increase in temperature depends on the mass of the substance heated, the type of material, and the energy input to the system. The following equation applies: change in thermal energy = mass × specific heat capacity × temperature change [Δ E = m c Δθ ] change in thermal energy Δ E in joules, J mass m in kilograms, kg specific heat capacity c in joules per kilogram per degree Celsius, J/kg °C temperature change Δθ in degrees Celsius, °C. The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius. ice cubes that have food colouring in them. Ask the students to describe the processes taking place. Main Internal energy (20 min) Begin heating the beaker of iced water and discuss the energy transfers involved. Initially there will be no temperature increase, allowing discussion of the latent heat and the repositioning of the bonds of the particles. As the ice melts and the temperature starts to increase, begin to describe the changes in motion for the particles. By the time the water is boiling, the students should have a good understanding of internal energy. Particle behaviour (20 min) Describe the behaviour of the particles in a solid, liquid, and gas with a focus on the forces between the particles. Describe the attraction between individual particles and how the motion changes. Additional details about the behaviour of gases will be covered in the next few lessons. Plenaries Convection revisited (10 min) Repeat the second starter, but ask the students to describe the changes in particle behaviour for the ice. What forces? (5 min) Can the students describe forces are responsible for attraction and repulsion between molecules and Aiming for Grade 8 LOs: Use the concepts of kinetic and potential energy to explain changes in internal energy. Describe the changes in the size of intermolecular forces during changes of state.
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