1. Physical change
Describe the rearrangement of molecules that occurs during physical changes e.g. the sublimation of iodine and the boiling of water; show using both labelled diagrams and equations how:
o   molecules are separated  
o   disordering of particles due to breaking of intermolecular forces  
o   energy change are small in relation to chemical changes find energy values
o    mass and numbers of atoms and molecules as being conserved during these physical changes.

2. Phases of Matter PLASMA GAS LIQUID Solid
The FOUR states of matter are determined by the amount of …………………. available. +
PLASMA
GAS
LIQUID
Solid

3. Phases of Matter LIQUID Solid INCREASING ENERGY PLASMA GAS
o   molecules are separated
  spaces increase
o   disordering of particles due to breaking of intermolecular forces  strong forces weak forces
o   energy change are small in relation to chemical changes find energy values
Energy of Vaporisation: 2270 kJ/kg
118 kcal to decompose 2 moles of H2O 493.7kJ = kJ/kg
o    mass and numbers of atoms and molecules as being conserved during these physical changes.
H2O(s)  H2O (l) no atoms or mass lost!
H2O +
PLASMA
Highly disordered
INCREASING ENERGY
GAS
LIQUID
Highly ordered
Solid
The FOUR states of matter are determined by the amount of ENERGY available.

4. Phases of Matter SOLID LIQUID GAS PLASMA POSITION/ ArrangementShape
FORCES
ENERGY/ Movement

5. Phases of Matter SOLID LIQUID GAS PLASMA POSITION/ ArrangementShape
Fixed
Random Take shape of container
Random Fill any container
Changing
FORCES
Very Strong
Weakened
Very weak
None
ENERGY/ Movement
Low energy vibrate
Higher Slide over each other
High – Rapid random motion
High – particles breaking up

6. Phase changes GAS LIQUID Solid o molecules are separated
  spaces increase
o   disordering of particles due to breaking of intermolecular forces  strong forces weak forces
o   energy change are small in relation to chemical changes find energy values
Energy of Vaporisation (Physical change)
H2 O(l)  H2O (g) : 2270 kJ/kg
Chemical Change 118 kcal to decompose 2 moles of H2O
493.7kJ = kJ/kg
H2 O(l)  H2 (g) + O2 (g)
o    mass and numbers of atoms and molecules as being conserved during these physical changes.
H2 O(s)  H2O (l) no atoms or mass lost!
GAS
LIQUID
Solid

7. Phase Changes Solid Liquid Liquid  Gas Solid  GAS Process
PARTICLE (positions)
FORCES
Force
ENERGY

8. Energy required/taken or put in
Phase Changes
Solid Liquid
Liquid  Gas
Solid  GAS
Process
Evaporation or boiling
sublimation
PARTICLE (positions)
Random  more random
Slide over each other completely free movement
Fixed  random rapid completely free
FORCES
Forces weakened
Forces broken
Broken
ENERGY
Energy required/taken or put in

9. Melting (Fusion) Melting
When a solid melts the particles need to undergo a number of changes:
Solid --> Liquid:
the spaces between the particles increase
The energy of the particles increases
The forces between the particles are weakened
Each of these changes requires energy to be put in.
The temperature stays constant because the extra energy is being used to weaken the forces.
Melting

10. Boiling/(Evaporation)
When a liquid boils the particles need to undergo a number of changes:
Liquid --> Gas:
the spaces between the particles increase
The energy of the particles increases
The forces between the particles are weakened
Each of these changes requires energy to be put in.
The temperature stays constant because the extra energy is being used to weaken the forces.
Gas
Boiling/ (Evaporation )
Liquid

11. Condensation When a gas condenses:
the spaces between the particles decrease.
The energy of the particles decreases (move slower).
The forces between the particles are strengthened.
Each of these changes requires energy to be taken out. (Given off).
Gas
Energy given off
Energy given off
Condensing
Liquid
The temperature stays constant because strengthening forces releases energy which replaces that which has been removed.

12. Freezing
When a liquid freezes (fuses) the particles need to undergo a number of changes:
Liquid --> solid:
the spaces between the particles decrease.
The energy of the particles decreases (move slower).
The forces between the particles are strengthened.
Each of these changes requires energy to be taken out. (Given off).
Energy taken out
Energy taken out
Fusion
The temperature stays constant because strengthening forces releases energy which replaces that which has been removed.

13. Phase Change - Snow
Explain why the air is warmer when it snows than when the snow is thawing (melting).
This energy is lost to the surrounding air as heat which makes it feel warmer.

14. Phase Change - Snow
When water freezes to form snow – the particles (water molecules) must lose energy.
This energy is lost to the surrounding air as heat which makes it feel warmer.
The reverse process makes it feel much colder when the snow begins to melt.

15. Boiling vs Evaporation
GAS
Wind
LIQUID
Water molecules (high energy) escape from the surface of the liquid.
The remaining particles have less energy - lower temperature
ENERGY IS REMOVED FROM THE WATER (Cooling Effect).
All liquids have their own vapour (gas).
This vapour has a pressure which increases with temperature.
When the vapour pressure equals the pressure outside the liquid the liquid boils.
IN BOILING ENERGY MUST BE PUT IN.
The temperature of the water does not change as the energy is used to change the phase.

16. Phase Changes Bonds inside particles (intramolecular) do NOT break! H
High energy molecules escape! O H
Molecule escapes!
GAS
Wind
Forces broken! O H O H O H
Boiling & evaporation are both phase changes – intermolecular bonding is involved in phase changes – intra molecular bonding is not. O H
Forces between particles (intermolecular) breaking.

17. Phase Changes Solid Liquid Liquid  Gas Solid  GAS Process
PARTICLE (positions)
FORCES
ENERGY

18. Boiling vs Evaporation
Similarities
Change water to water vapour
Particles undergo same changes (increase spaces, energy, weaker forces)
Differences
High Temp
Energy put in
Affected by atmospheric pressure
Low Temp
Energy taken out.
Not affected by pressure.

19. Graph of temperature change vs time for the heating of a sample of ice.
Heating Curve
During a phase change the energy is used to overcome forces between the particles and increase the spaces between them - the temperature stays the same so the graph is flat.
Water boiling
Temperature o C
Water heating up
Ice - melting

20. Phases Task
Find out the melting point and boiling points of the following substances.
Hydrogen oxide (H2O) Mp: 0oC, Bp: 100oC
Nitrogen - gas 80% of the air
(N2) Mp: -210oC, Bp: -195oC
Mercury - liquid Mp: -39oC, Bp: 357oC
What factors can affect the boiling point of water?
Altitude (pressure) - higher (alt) --> lower (bp)
Dissolved substances --> raise the boiling point.