2. Thermal physics

• Know the distinguishing properties of solids, liquids and gases

• Know the terms for the changes in state between solids, liquids and gases (gas to solid and solid to gas transfers are not required)

• Describe the particle structure of solids, liquids and gases in terms of the arrangement, separation and motion of the particles and represent these states using simple particle diagrams

• Describe the relationship between the motion of particles and temperature, including the idea that there is a lowest possible temperature (−273 °C), known as absolute zero, where the particles have least kinetic energy

• Describe the pressure and the changes in pressure of a gas in terms of the motion of its particles and their collisions with a surface

• Know: the random motion of microscopic particles in a suspension is evidence for the kinetic particle model of matter

• Describe and explain this motion (sometimes known as Brownian motion) in terms of random collisions between the microscopic particles in a suspension and the particles of the gas or liquid

• Know: the forces and distances between particles (atoms, molecules, ions and electrons) and the motion of the particles affects the properties of solids, liquids and gases

• Describe the pressure and the changes in pressure of a gas in terms of the forces exerted by particles colliding with surfaces, creating a force per unit area

• Know: microscopic particles may be moved by collisions with light fast-moving molecules and correctly use the terms atoms or molecules as distinct from microscopic particles

• Describe qualitatively, in terms of particles, the effect on the pressure of a fixed mass of gas of: (a) a change of temperature at constant volume (b) a change of volume at constant temperature

• Convert temperatures between kelvin and degrees Celsius; recall/use: T (in K) = θ (in °C) + 273

• Recall/use: pV = constant for a fixed mass of gas at constant temperature, including a graphical representation of this relationship

• Describe qualitatively the thermal expansion of solids, liquids and gases at constant pressure

• Describe some of the everyday applications and consequences of thermal expansion

• Explain, using particle motion and arrangement, the relative order of magnitudes of the expansion of solids, liquids and gases as their temperatures rise

• Know: a rise in the temperature of an object increases its internal energy

• Describe an increase in temperature of an object in terms of an increase in the average kinetic energies of all of the particles in the object

• Define specific heat capacity as energy required per unit mass per unit temperature increase; recall/use: c = ΔE/(mΔT)

• Describe experiments to measure the specific heat capacity of a solid and a liquid

• Describe melting and boiling in terms of energy input without a change in temperature

• Know the melting and boiling temperatures for water at standard atmospheric pressure

• Describe condensation and solidification in terms of particles

• Describe evaporation in terms of the escape of more-energetic particles from the surface of a liquid

• Know: evaporation causes cooling of a liquid

• Describe the differences between boiling and evaporation

• Describe how temperature, surface area and air movement over a surface affect evaporation

• Explain the cooling of an object in contact with an evaporating liquid

• Describe experiments to demonstrate the properties of good thermal conductors and bad thermal conductors (thermal insulators)

• Describe thermal conduction in all solids in terms of atomic or molecular lattice vibrations and also in terms of the movement of free (delocalised) electrons in metallic conductors

• Describe, in terms of particles, why thermal conduction is bad in gases and most liquids

• Know: there are many solids that conduct thermal energy better than thermal insulators but do so less well than good thermal conductors

• Know: convection is an important method of thermal energy transfer in liquids and gases

• Explain convection in liquids and gases in terms of density changes and describe experiments to illustrate convection

• Know: thermal radiation is infrared radiation and that all objects emit this radiation

• Know: thermal energy transfer by thermal radiation does not require a medium

• Describe the effect of surface colour (black or white) and texture (dull or shiny) on the emission, absorption and reflection of infrared radiation

• Know: for an object to be at a constant temperature it needs to transfer energy away from the object at the same rate that it receives energy

• Know what happens to an object if the rate at which it receives energy is less or more than the rate at which it transfers energy away from the object

• Know how the temperature of the Earth is affected by factors controlling the balance between incoming radiation and radiation emitted from the Earth’s surface

• Describe experiments to distinguish between good and bad emitters of infrared radiation

• Describe experiments to distinguish between good and bad absorbers of infrared radiation

• Describe how the rate of emission of radiation depends on the surface temperature and surface area of an object

2.3.4.1Some of the basic everyday

• Explain some of the basic everyday applications and consequences of conduction, convection and radiation, including: (a) heating objects such as kitchen pans (b) heating a room by convection

2.3.4.2Applications/consequences where

• Explain applications/consequences where conduction, convection and radiation all matter, including: (a) a fire burning wood or coal (b) a car radiator