Topic 14-Particle Model

• What is the formula for density?

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

  kgm^-3
• How does density vary between solids, liquids, and gases?

  Solids and liquids have similar densities
• What is the main exception to the density rule between solids and liquids?

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

  Particles are spaced further apart in gases
• 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 weigh?

  20g
• Why are changes of state considered physical changes?

  Materials retain original properties when reversed
• What happens to the energy of particles when a system is heated?

  The energy of the particles increases
• What occurs to the temperature of a system when it changes state?

  The temperature may increase or remain constant
• What are the changes of state for solids, liquids, and gases?

  • 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?

  Energy required to raise 1kg by 1°C
• What is the formula for calculating energy using specific heat capacity?

  $E =$$mc\Delta T$
• What is specific latent heat?

  Energy to change state without temperature change
• What is the specific latent heat of fusion?

  Energy to melt or freeze a substance
• What is the specific latent heat of vaporisation?

  Energy 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 effect of thermal insulation on energy transfer?

  It reduces energy lost to surroundings
• What is the formula for pressure?

  $pressure =$$\frac{force}{area}$
• How do particles in a gas move?

  Randomly in every direction
• What happens when gas particles collide with a wall?

  They change velocity and exert force
• How does temperature affect pressure in a gas at constant volume?

  Increased temperature increases pressure
• What is absolute zero in Kelvin?

  0 Kelvin
• What is absolute zero in Celsius?

  -273°C
• What occurs at absolute zero?

  Particles have no energy and remain still
• How do you convert Kelvin to Celsius?

  $T_{kelvin} =$$T_{centigrade} +$$273$
• What happens to gas pressure when volume decreases?

  Pressure increases as volume decreases
• What is the relationship between pressure and volume for a gas at fixed mass and temperature?

  Pressure is inversely proportional to volume
• What is the formula relating pressure and volume?

  $P_1V_1 =$$P_2V_2$
• What happens when work is done on a gas?

  Its temperature increases
• What is the formula for work done on a gas?

  $W_D =$$F \times d$
• What happens when more gas is added to a fixed volume?

  Pressure increases due to more collisions
• What occurs when the volume of a gas decreases with a fixed number of particles?

  Pressure increases and temperature rises
• What are the effects of compressing a gas?

  • Increases pressure
  • Increases temperature
  • More frequent collisions with walls