Equation for density should be known. density, ρ, in kilograms per metre cubed, kg/m3 mass, m, in kilograms, kg volume, V, in cubed, m3 Convert non-standard units into standard units for calculations. Recall the equation for density and it. Calculate the density, mass or volume of an object given any two other values. determine the densities of regular and irregular objects and liquids. Volume should be determined from the dimensions of regularly shaped objects and by a displacement technique for irregularly shaped objects. Dimensions to be measured using appropriate apparatus such as a ruler, micrometer or Vernier callipers. (10.2.17) Why do objects float? This topic can be linked to the above investigation as once you know the density of an object you can predict if it floats or sinks in water. 6.3.1.1 The particle model of matter. The particle model can be used to explain the different states of matter. 1 Draw diagrams to show the particle arrangements in solids, liquids and gases. Describe and explain the different particle arrangements in solids, liquids and gases due to the bonds between the atoms. Describe the motion of particles in solids, liquids and gases. Describe and explain the limitations of the particle model of Why are models used in Physics? Critically evaluate the models used to describe and explain the behaviour of solids, liquids and gases. If you have a kinetic model, you can use it to demonstrate the motion of particles in a liquid/gas. If you don’t have a
their arrangement that has altered. Describe the changes of state in terms of solids, liquids and gases. 6.3.1.2 Chemical and physical changes. Changes of state are physical changes; the change does not produce a new substance. If the change is reversed the substance recovers its original properties. 0.5 What is the difference between a chemical and a physical change? Describe the difference between a chemical and a physical change and provide examples for both types. Describe how, if a physical change is reversed, the substance will recover its original properties. Demonstrate physical and chemical changes and, where possible, the reversibility of a physical change, eg melting ice and then refreezing. 6.3.2 Internal energy and energy transfers Spec ref. Summary of the specification content Learning outcomes What most candidates should be able to do Suggested timing (hours) Opportunities to develop Scientific Communication skills Opportunities to develop and apply practical and enquiry skills Self/peer assessment opportunities and resources Reference to past questions that indicate success
6.3.2.1 Internal energy of a system. Heating and temperature. Energy is stored inside a system by the particles (atoms and molecules) that make up the system. This is called internal energy. Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system. Heating changes the energy stored within the system by increasing the energy of the particles that make up the system. And, either the temperature of the system increases, or changes of happen. 1 What effect does increasing the temperature of an object have on the that make up the object? Describe temperature being a measure of the average kinetic energy of the particles in a substance. Describe and explain how increasing the temperature of a substance affects the internal energy of a substance. Define internal energy. Explain how the strength of the bonds between the particles will affect how much energy is needed to change the state of the substance. Evaluate data on the melting points and boiling points of different substances linked to the strength of the forces between the particles. Explain what is happening at each stage of the heating curve produced. Model the behaviour of atoms within a solid as it is heated past its melting point. You can use the tray of ping-pong balls or the kinetic theory apparatus if available. Critically analyse the model and suggest improvements to it. Investigate the heating curve for water by heating some ice in a beaker until the water evaporates. Use temperature sensors/data loggers to record the temperature at fixed intervals, eg 30 seconds. A graph can be plotted of temperature against time. 6.3.2.2 Specific heat capacity. If the temperature of the system increases: the increase in temperature depends on the mass of the substance heated, what the 1 Describe and explain how the amount of water in a kettle affects how quickly it boils. Plan a practical to investigate the rate of heating of various metals using a joulemeter to determine the energy input. If
substance is and the energy input to the system. The following equation applies: change in thermal energy, ∆E, in joules, J mass, m, in kilograms, kg specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg oC temperature change, ∆θ, in degrees Celsius, oC The specific heat capacity of a substance is the amount of energy required to the temperature of one kilogram of the substance by one degree Celsius. Explain why a pan of cooking oil heats up faster than a pan of water, with the same mass of each, in terms of specific heat capacity. Why is water used in central heating systems? Define specific heat capacity. Describe the factors that affect how quickly the temperature of a substance increases, eg why does a half-full kettle heat up faster than a full kettle of Calculate the change in thermal energy, mass, specific heat capacity or the temperature change of a substance that is heated or cooled. The equation will be provided on the equations sheet. Students should be able to convert to SI units and use standard form in their answers. Explain why special concrete blocks are used in storage heaters. no joulemeter is available, use an ammeter, I, a voltmeter, V, and heat the material for a fixed amount of time, t. Calculate the energy transferred, E, using: Determine the specific heat capacity of water by experiment.
6.3.2.3 Specific latent heat. If a change of state happens: The energy needed for a substance to change state is called latent heat. When a change of state occurs, the energy supplied changes the energy stored (internal energy), but not the temperature. The specific latent heat of a substance is the amount of energy required to change the state of one kilogram of the substance with no change in temperature: energy, E, in joules , J mass, m, in kilograms, kg specific latent heat, L, in joules per kilogram, J/kg Specific latent heat of fusion – change of state from solid to liquid. Specific latent heat of vaporisation – change of state from liquid to vapour. 1 Define specific latent heat. Draw heating and cooling graphs for a substance including a change of state. Interpret a heating or cooling graph to explain what is happening at each stage of the graph. Explain why a of ice at 0 °C that is being heated does not increase in temperature initially. Calculate the energy for a change of state, mass or specific latent heat of a substance given the other values. Students will be expected to convert to SI units and use standard form where required. Evaluate the use of different coolants used in fridges in terms of the specific latent heat of the coolant and the boiling point of the coolant. Research the use of coolants in fridges. Define specific latent heat of fusion and vaporisation. Explain why the specific latent heat of vaporisation is greater Plan and out an investigation to find the specific latent heat of fusion of water. Investigate the heating for water by heating some ice in a beaker until the water evaporates. Use temperature sensors/data loggers to record the temperature at fixed intervals, eg 30 seconds. A graph can be plotted of temperature against time. Instead of the above carry out the Institute of Physics investigation from Episode 608-2:
average kinetic energy and so the faster the average of the molecules. Describe and explain how the motion of molecules in a gas changes as the gas is heated. Why are gas cylinders likely to explode in a fire? use Institute of Physics’ Episode 601-1: 6.3.3.1 How gases exert forces on the walls of their containers. When the molecules collide with the wall of their container they exert a force on the wall. The total force exerted by all of the molecules inside the container on a unit area of the walls is the gas pressure. 0.5 Describe why gases exert a force on a container. Explain what is meant by gas pressure in terms of the forces exerted by the gas molecules on a given area. Explain how blowing up a balloon too much can cause it to pop in terms of gas pressure. Research how the gas pressure in a submarine it from crushing at depth. Use PhET interactive simulations to model gas pressure: 6.3.3.1 How changing the temperature of a gas affects the pressure exerted. Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas (known as the Pressure law). 1 Describe and explain how changing the temperature of gas increases the gas pressure inside the container. Explain why gas cylinders should not be placed near heat sources. Evaluate newspaper articles of local fires that have involved gas canisters exploding and the reasons for the explosion in terms of gas pressure. Why do aerosol deodorants say: keep away from fire? what is happening inside a container of fixed volume when the temperature is changed. Investigate the Pressure law: a round-bottomed flask connected to a pressure gauge in a container of water. Heat the water taking the temperature and pressure. Plot a of pressure against temperature. BBC Bitesize – Temperature and gas calculations clip YouTube: