4.3.2.3 Changes of State and Specific Latent Heat

Question 1

Heating curve (heating a system + explanation):

Answer 1

• Solid
  
  • temp increase as kinetic E of particles increase
• Melting
  
  • changing state
  • potential E increase (so increasing internal E store of system but not changing temp as average kinetic E of particles stays the same)
  • temps is constant
  • energy being put into system is weakening or breaking the forces of attraction between the particles allowing the substance to change state to a liquid
• Liquid
  
  • temp increase as kinetic E of particles increases
• Boiling
  
  • changing state
  • potential E increase (so increasing internal E store of system but not changing temp as average kinetic E of particles stays the same)
  • temps is constant
  • energy being put into system is weakening or breaking the forces of attraction between the particles allowing the substance to change state to a gas
• Gas
  
  • temp increase as kinetic E of particles increases

Question 2

Cooling curve (cooling a system):

Answer 2

Question 3

Latent heat:

Answer 3

the energy needed for a substance to change state

Question 4

Specific latent heat:

Answer 4

the specific latent heat of a substance is the amount of energy required to change the state of one kg of the substance with no change in temperature

Question 5

Specific latent heat of fusion:

Answer 5

the energy required to change 1kg of a substance from a solid to a liquid (or liquid to solid) with no change in temp

Question 6

Specific latent heat of vaporisation:

Answer 6

the energy required to change 1kg of a substance from a liquid to vapour (or vapour to liquid) with no change in temperature

Question 7

Formula to calculate energy for change of state:

Answer 7