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neurologyYou need to know

• In a solid, particles are arranged in a regular or fixed pattern and vibrate about fixed positions.
• In a liquid, particles are close together but arranged irregularly, and they can move past each other.
• In a gas, particles are far apart, arranged randomly, and move rapidly in all directions.
• Solids have a fixed shape and a fixed volume because strong forces hold their particles close together in fixed positions.
• Liquids have a fixed volume but no fixed shape because their particles remain close together but can flow past each other.
• Gases have no fixed shape or fixed volume because their particles have very weak forces between them and are far apart.
• Density is mass per unit volume, and it is calculated using `density = mass \div volume`.
• The units of density are usually kilograms per cubic metre, `kg/m^3`, or grams per cubic centimetre, `g/cm^3`.
• Most solids are denser than liquids and gases because their particles are packed more closely together, while gases have very low density because their particles are far apart.
• The temperature of a substance is related to the average kinetic energy of its particles.
• Internal energy is the total kinetic energy and potential energy of all the particles in a substance.
• Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C without changing state.
• Specific latent heat is the energy needed to change the state of 1 kg of a substance at constant temperature.
• During melting, freezing, boiling, condensing and sublimation, energy changes the potential energy of particles rather than the temperature of the substance.
• A pure substance has a sharp melting point and boiling point, while impurities cause melting and boiling to happen over a range of temperatures.
• On a heating or cooling graph, sloping sections show temperature change and flat sections show a change of state at constant temperature.
• Gas particles move in rapid random motion and collide with each other and with the walls of their container.
• Gas pressure is caused by gas particles colliding with the walls of their container and exerting a force on them.
• For a fixed mass of gas at constant volume, increasing the temperature increases the pressure because particles move faster and collide more often and more forcefully with the container walls.
• For a fixed mass of gas at constant temperature, pressure and volume are inversely proportional, so `pV = constant`.

• Draw particle diagrams for solids, liquids and gases, showing the spacing, arrangement and motion of particles accurately.
• Explain the properties of solids, liquids and gases by linking particle arrangement, particle energy and the strength of forces between particles.
• Calculate density using `density = mass \volume`, choosing correct units and rearranging the equation when needed.
• Measure the density of a regular solid by measuring its mass with a balance, calculating its volume from its dimensions, and using `density = mass \volume`.
• Measure the density of an irregular solid by measuring its mass with a balance, finding its volume using water displacement, and using `density = mass \volume`.
• Measure the density of a liquid by finding the mass of a known volume of liquid and using `density = mass \div volume`.
• Interpret heating and cooling graphs by identifying temperature changes, changes of state, melting points and boiling points.
• Calculate the pressure or volume of a fixed mass of gas at constant temperature.
• Explain how doing work on a gas increases its internal energy and can increase its pressure by making particles collide more frequently and forcefully with the container walls.