Particle Model of Matter

• What is the formula for density?

  $\rho =$$\frac{m}{V}$
• What units are used for density?

  Density is measured in kilograms per metre cubed (kg/m³).
• How does density depend on the spacing of atoms in matter?

  Density depends on the spacing of the atoms; solids and liquids have similar densities due to minimal spacing change.
• Which usually has a lower density, solids or liquids?

  Liquids usually have a lower density than solids, with the exception of ice and water.
• Why do gases have a far lower density compared to solids and liquids?

  Gases have a far lower density because the spacing between atoms increases significantly, leading to a greater volume.
• What happens to mass during a change of state?

  Mass is conserved during a change of state.
• If 20g of liquid evaporates, how much does the gas produced weigh?

  The gas produced will also weigh 20g.
• What distinguishes physical changes from chemical changes during state changes?

  • Physical changes are reversible.
  • The material retains its original properties when reversed.
• What are the changes of state between solid, liquid, and gas?

  • Melting: Solid to Liquid
  • Freezing: Liquid to Solid
  • Evaporating: Liquid to Gas
  • Condensing: Gas to Liquid
  • Sublimation: Solid to Gas
• What is internal energy?

  Internal energy is the energy stored by particles within a system, including kinetic and potential energy.
• What happens to the internal energy of a system when it is heated?

  Heating increases the energy of the particles, raising the internal energy.
• What is specific heat capacity?

  Specific heat capacity is the amount of energy required to raise the temperature of 1kg of a substance by 1°C.
• What is the formula for change in thermal energy?

  $\Delta E =$$m \times c \times \Delta T$
• What is specific latent heat?

  Specific latent heat is the amount of energy needed to change the state of 1kg of a substance without a change in temperature.
• What is the specific latent heat of fusion?

  Specific latent heat of fusion is the energy required to melt or freeze a substance.
• What is the specific latent heat of vaporisation?

  Specific latent heat of vaporisation is the energy required to boil or condense a substance.
• What happens to energy during melting and evaporating?

  Energy is absorbed when melting and evaporating.
• What happens to energy during freezing and condensing?

  Energy is released when freezing and condensing.
• What is sublimation?

  Sublimation is when a solid goes straight to gas, such as dry ice (solid CO₂).
• Describe the temperature changes of ice as it transitions to gas.

  • At A: Ice (Solid)
  • At B: Reaches 0°C
  • From B to C: No temperature change (melting)
  • From C to D: Liquid state
  • From D to E: Water boiling (takes longer)
  • From E to F: Gas heating
• How is the temperature of a gas related to the average kinetic energy of its molecules?

  The temperature of a gas is related to the average kinetic energy of the molecules; higher temperature means greater average kinetic energy.
• What happens when gas molecules collide with the walls of their container?

  When gas molecules collide with the walls, they exert a force, contributing to gas pressure.
• What is the Pressure law in relation to gas temperature and pressure?

  Changing the temperature of a gas at constant volume changes the pressure exerted by the gas.
• What is Boyle's law regarding gas volume and pressure?

  Boyle's law states that increasing the volume of a gas at constant temperature leads to a decrease in pressure.
• What is the formula that relates pressure and volume for a gas at fixed mass and temperature?

  $P_1 V_1 =$$m c$
• What happens when work is done on a gas?

  Doing work on a gas increases its temperature.
• How does adding more particles to a fixed volume affect gas pressure?

  Adding more particles increases the number of collisions with the walls, thus increasing pressure.
• What occurs when the volume of a gas is decreased?

  Decreasing the volume causes particles to collide with the walls more frequently, increasing pressure.
• How does the kinetic energy of particles change when the volume is decreased?

  The kinetic energy of each particle increases as the velocity increases due to more frequent collisions.