Physics CP12 Particle Model

• What is the difference between a solid, liquid, and gas?

  Solids have fixed shape, liquids take the shape of their container, and gases fill their container.
• How are particles arranged in solids, liquids, and gases?

  In solids, particles are tightly packed; in liquids, they are close but can move; in gases, they are far apart and move freely.
• How can you calculate the density of a substance?

  Density is calculated by dividing mass by volume.
• Describe two properties of solids, liquids, and gases.

  • Solids: Rigid, particles vibrate in fixed positions.
  • Liquids: Flow easily, particles are close but not fixed.
  • Gases: Fill their container, particles move freely and are far apart.
• What is a glacier?

  A glacier is a frozen river.
• What does the kinetic theory state about particles in solids?

  In solids, atoms or molecules are tightly held together and can only vibrate.
• Why are solids rigid and cannot be compressed?

  Because the particles are tightly packed and can only vibrate.
• How do particles behave in liquids?

  Particles in liquids move and have some freedom of movement but are still close together.
• Why can liquids flow and are not easily compressed?

  Because the particles are near enough to hold onto one another but not tightly packed.
• What characterizes gas particles?

  Gas particles are far apart, move quickly, and have little attraction to each other.
• Why are gases easily compressed and expand to fill their container?

  Because the particles are far apart and have little attraction to each other.
• What happens to particles during a change of state?

  The arrangement and energy of particles change, but the number of particles remains the same.
• Why is a change of state considered a physical change?

  Because there is no change in chemical properties and the change is reversible.
• What is density?

  Density is a measure of mass per unit volume of a substance.
• How does the density of a liquid depend on its particles?

  A liquid's density depends on how closely the particles are packed together.
• Calculate the density of a 20kg mass with a volume of 5 litres.

  $\text{Density} =$$\frac{20 \text{ kg}}{5 \text{ litres}} =$$4 \text{ kg/litre}$
• What is the density of a 400kg block of aluminium with a volume of 2 m³?

  $\text{Density} =$$\frac{400 \text{ kg}}{2 \text{ m}^3} =$$200 \text{ kg/m}^3$
• Calculate the volume of 5 tonnes (5000kg) of solid copper with a density of 8960kg/m³.

  $\text{Volume} =$$\frac{5000 \text{ kg}}{8960 \text{ kg/m}^3} \approx 0.557 \text{ m}^3$
• Which substance is denser, oil or water?

  Water is denser than oil.
• Why do liquids flow?

  Liquids flow because their particles have some freedom of movement.
• Why can gases be compressed?

  Gases can be compressed because their particles are far apart and have little attraction to each other.
• Why are water molecules less closely packed when changing from liquid to gas?

  Water molecules are less closely packed in gas because they have more energy and move faster.
• Why does a substance expand when heated?

  A substance expands when heated because the particles gain energy and move further apart.
• Why does a liquid take the shape of its container?

  A liquid takes the shape of its container because its particles can move freely and flow.
• Why can't solids be compressed while gases can?

  Solids cannot be compressed because their particles are tightly packed and cannot move closer together.
• Explain density in terms of mass and volume.

  Density is the mass of a substance divided by its volume.
• Calculate the density of ice if the density of water is 1000kg/m³.

  Density of ice is less than 1000kg/m³ due to its structure.
• Why does the density of a substance depend on temperature?

  The density of a substance can change with temperature due to expansion or contraction of particles.
• How can the kinetic theory model explain diffusion in air of solids and gases?

  Diffusion occurs because particles move randomly and spread out in the air.
• What are the steps to measure the density of a liquid and a solid?

  For liquids:

  1. Measure the mass of an empty beaker.
  2. Add a known volume of liquid and measure the mass again.
  3. Calculate density using the formula.

  
  

  For solids:

  1. Measure the mass of the solid.
  2. Use water displacement to find the volume.
  3. Calculate density using the formula.
• What are the differences in density between different concentrations of salty water?

  • Higher concentration = higher density
  • Lower concentration = lower density
  • Density changes due to the amount of dissolved salt.
• What apparatus is needed to investigate the density of solids and liquids?

  • Balance
  • Measuring cylinder
  • Beaker
  • Water for displacement
• What method would ensure a fair test when investigating densities?

  • Use the same temperature for all measurements.
  • Measure the same volume for each liquid.
  • Ensure consistent measurement techniques.
• What are the suitable units for calculating density?

  • Mass: kilograms (kg)
  • Volume: cubic meters (m³) or litres (L)
  • Density: kilograms per cubic meter (kg/m³) or kilograms per litre (kg/L)
• What are the changes involved in the state of solids and liquids?

  • Changes involve:
  • Movement of particles
  • Spacing between particles
• What are the basic needs for matter?

  Temperature and energy
• How do energy transfers affect substances?

  They can change the state of the substances
• What is latent heat?

  The energy needed to change 1kg of a substance from one state to another at a constant temperature
• What happens to the molecules of a solid when it is heated?

  The molecules gain kinetic energy and vibrate more
• What occurs when a solid melts?

  The particles gain enough kinetic energy to overcome the forces holding them together