AQA GCSE Physics: Particle Model of Matter

• What is density?

  mass per unit volume
• Why do helium balloons float?

  helium is less dense than air
• Why does wood float in water?

  wood is less dense than water
• What is the equation for density?

  Density = mass/volume
• What are the units of measurement for the equation to work out density?

  density - kg/m3mass - kgvolume - m3
• How much is 1g/cm3 in kg/m3?

  1g/cm3 = 1000kg/m3
• What is the force that holds a solid afloat?

  Upforce
• How does an object float?

  If its' density is lower than the liquids'.
• What is matter?

  Anything that has mass and takes up space
• What happens when a change of state occurs?

  The temperature stays the same. Only physical changes happen - no chemical changes. The volume changes but mass stays the same because the number of particles don't change.
• What is the point called when a liquid turns into a solid?

  Freezing point
• Which state has the lowest density?

  Gases
• What is the energy that is transferred to an object when it changes state called?

  Latent heat
• Why does the temperature stay the same?

  Energy is being put into making/ breaking the forces of attraction.
• What are some limitations of the particle model?

  doesn't show the forces of attraction between particleseach particle is represented by a solid, inelastic spherical shape.
• Properties of solids.

  have a fixed shapecannot be squashedcannot flowparticles cannot move
• Properties of a liquid.

  no fixed shapecannot be squashedcan flow
• Properties of gases.

  no fixed shapecan be squashedcan flow
• What is internal energy?

  Sum of kinetic and potential energy.
• What happens when particles are heated?

  Particles gain more thermal energy and so take up more room and expand.
• How can heating be proven?

  Particles gain more thermal energy and so take up more room and expand.
• Problems with expansion

  buildingfriction
• Uses of expansion

  Mercury in thermometers
• What is the formula used to workout the change in internal energy?


  Change in internal energy = mass x shc x change in temp
• What happens when a substance's physical state changes?

  The total potential energy changes.
• Why is pressure created?

  Pressure is created by the particles hitting the surface repeatedly.
• What happens when you heat a substance?

  internal energy increases and physical state changes
• What is meant by the term specific latent heat of fusion?

  The amount of energy needed to change 1kg of a substance from solid to liquid without changing the temperature.
• What is meant by the term specific latent heat of vaporisation?

  The amount of energy needed to change 1kg of a substance from a liquid to a vapour without changing the temperature.
• What is the equation for the energy needed to change a substance to another state?

  energy for a change of state = specific latent heat x mass
• What is the equation for specific latent heat?

  energy / mass
• What is the specific latent heat of ice measured using?

  A low voltage heater
• Define brownian motion

  random movement of particles in a fluid
• What causes the walls of a container to expand when a gas is in there?

  The increase in temperature causes an increase in kinetic energy which means the particles begin to move faster and exert a greater force on the sides of the walls of the container
• A gas has a volume of 5m^3 and a pressure of 150000 Pa. The pressure decreases to 50000 Pa. Calculate the volume.

  15m^3
• How is gas pressure connected to the temperature?

  directly proportional
• What must stay constant for the gas pressure to be directly proportional to the temperature?

  volume
• Properties of solids

  have a fixed shapecannot be compressedcannot flowparticles cannot move, only vibrate
• Why do solids have a fixed shape?Why can they not be compressed?

  The particles cannot move from place to placeAs they are very close together, they have no space to move into so cannot be compressed
• Properties of liquids

  no fixed shapecannot be compressedcan flow