Particle model

• What is the formula for density?

  $\rho =$$\frac{m}{V}$
• What are the units of density?

  kgm⁻³
• How does density depend on the spacing of atoms in matter?

  Density is influenced by how closely packed the atoms are in a substance.
• Why do solids and liquids have similar densities?

  Because the space between particles does not change significantly in solids and liquids.
• What is the main exception to the rule that liquids usually have a lower density than solids?

  Ice and water.
• Why do gases have a far lower density compared to solids and liquids?

  Because the spacing between atoms increases significantly, leading to a larger volume and lower density.
• 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?

  20g.
• Why are changes of state considered physical changes rather than chemical changes?

  Because the material retains its original properties when reversed.
• What happens to the energy of particles when a system is heated?

  The amount of energy the particles have increases, causing them to vibrate more.
• What is the relationship between temperature and state change in a system?

  The temperature of the system increases or the system changes state.
• What are the different states of matter and their changes?

  • Solid to Liquid: Melting
  • Liquid to Gas: Evaporating
  • Liquid to Solid: Freezing
  • Gas to Liquid: Condensing
  • Solid to Gas: Sublimation
• What is specific heat capacity?

  The energy required to raise the temperature of 1kg of a substance by 1°C.
• What is the formula for calculating energy in relation to specific heat capacity?

  $E =$$mc\Delta T$
• What are the units for specific heat capacity?

  Jkg⁻¹°C⁻¹
• What is specific latent heat?

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

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

  The energy required to boil or condense a substance.
• What happens to energy during melting and evaporating?

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

  Energy is released.
• What is the formula for calculating energy in relation to specific latent heat?

  $E =$$ml$
• What are the units for specific latent heat?

  Jkg⁻¹
• What is the effect of thermal insulation on energy transfer?

  It reduces the amount of energy lost to the surroundings.
• How do reflective coatings help in insulation?

  They reflect infrared radiation (heat) back into the system.
• What is pressure in a gas?

  Pressure is the force per unit area.
• What happens when gas particles collide with a wall?

  They change velocity and exert a force on the wall.
• How does temperature affect the kinetic energy of gas particles?

  Increased temperature means more energy is given to the particles, increasing their speed.
• What is the relationship between temperature and pressure in a gas at constant volume?

  As temperature increases, pressure also increases due to more frequent and forceful collisions with the walls.
• What is absolute zero in Kelvin and Celsius?

  0 Kelvin or -273°C.
• What occurs at absolute zero?

  Particles have no energy and do not vibrate at all.
• How do you convert Kelvin to Celsius?

  $T_{kelvin} =$$T_{centigrade} +$$273$
• If the temperature is 4K, what is it in Celsius?

  • 269°C.
• If the temperature is 0°C, what is it in Kelvin?

  273K.
• What happens to gas pressure when the volume decreases?

  Pressure increases as the gas is compressed into a smaller volume.
• What happens to gas pressure when the volume increases?

  Pressure decreases as the gas expands into a larger volume.
• What is the relationship between pressure and volume in a gas?

  Pressure is inversely proportional to volume.
• What is the equation that relates pressure and volume for a gas at fixed mass and temperature?

  $P_1V_1 =$$P_2V_2$
• What happens to the temperature of a gas when work is done on it?

  The temperature of the gas increases.
• What is the formula for work done on a gas?

  $W_D =$$\text{Force} \times \text{distance}$
• How does adding more particles to a fixed volume affect gas pressure?

  It increases the pressure due to more collisions with the walls.