Particle model of matter flashcards

The particle model of matter explains how all substances are made up of tiny particles arranged and moving differently in solids, liquids and gases. In solids, particles are closely packed in fixed positions and vibrate; in liquids, particles are close together but can flow past each other; in gases, particles are far apart and move rapidly in random directions. Students must understand density as mass per unit volume and be able to calculate it. Changes of state involve energy transfers that change the arrangement and movement of particles without changing the particles themselves. The concept of internal energy as the total kinetic and potential energy of particles is important, as is latent heat, the energy needed to change state at constant temperature. Students should also understand how pressure in gases relates to particle collisions with container walls.

1. Card 1

   What is the definition of density?

   Density is the mass per unit volume of a substance. It is calculated using density = mass divided by volume, and is measured in kg/m3 or g/cm3.

2. Card 2

   How are particles arranged in a solid?

   In a solid, particles are packed closely together in a regular arrangement. They vibrate about fixed positions and cannot move freely, which is why solids have a definite shape.

3. Card 3

   How does particle movement differ in a gas compared to a liquid?

   In a gas, particles move rapidly in random directions and are far apart. In a liquid, particles are close together but can slide past each other, so movement is much more limited.

4. Card 4

   What happens to the temperature of a substance while it is changing state?

   Temperature stays constant during a change of state. The energy supplied goes into changing the arrangement of particles rather than increasing their kinetic energy.

5. Card 5

   What is latent heat?

   Latent heat is the energy needed to change the state of a substance without changing its temperature. Specific latent heat is the energy per kilogram needed for that change of state.

6. Card 6

   What is internal energy?

   Internal energy is the total kinetic energy and potential energy stored by all the particles in a substance. Heating a substance increases its internal energy.

7. Card 7

   What is specific heat capacity?

   Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius. It is measured in J/kg°C and varies between different materials.

8. Card 8

   How does gas pressure arise according to the particle model?

   Gas pressure is caused by particles colliding with the walls of their container. More frequent or harder collisions produce greater pressure.

9. Card 9

   What happens to gas pressure if the temperature increases at constant volume?

   Pressure increases because particles gain kinetic energy, move faster, and collide with the container walls more frequently and with greater force.

10. Card 10

    What is the difference between evaporation and boiling?

    Evaporation occurs at the surface of a liquid at any temperature, while boiling happens throughout the liquid at a fixed boiling point when bubbles of vapour form inside.

11. Card 11

    Why do different materials have different densities?

    Density depends on the mass of the particles and how closely they are packed together. Denser materials have heavier particles and or particles packed more tightly.

12. Card 12

    What is the formula for specific latent heat and what do the symbols mean?

    Q = m x L, where Q is energy transferred in joules, m is mass in kg, and L is specific latent heat in J/kg. This applies to melting or vaporisation.

• Many students think that during a change of state the energy supplied disappears or is wasted, when in fact it is stored as increased potential energy of the particles as they are separated.
• A common error is confusing specific heat capacity with specific latent heat, using the wrong formula when a question involves a change of state rather than a change in temperature.
• Students often assume that particles in a gas are moving slowly or are stationary, when in reality gas particles move very rapidly and randomly, which is what causes gas pressure.

Planning your revision? Read how to revise GCSE Physics, or make cards from your own notes with the notes to flashcards tool.