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States of MatterSOLID LIQUID GAS
Kinetic molecular theory
Explains the behaviour of the particles in all 3 states of matter
TB. pg 56
Model (textbook page 56)
1. PARTICLES
2. CONSTANT MOTION
3. SPACES
4. FORCES
5. COLLISIONS
6. AVERAGE KINETIC ENERGY CONSTANT
TB. pg 56
Robert Brown
“Brownian Movement”
The random movement of microscopic particles suspended in a liquid or gas, caused by collisions with molecules of the surrounding medium.
TB. pg 45
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Important Definitions
Diffusion
Movement of the particles of a substance in between particles of a second substance – from an area of highconcentration to an area of lowconcentration
TB. pg 46
SOLIDS• Particles only vibrate
• Extremely small spaces between the spaces
• Very strong forces between the particles
• Diffusion does not occur
• Cannot be compressed
• Retains its shape
• Particles arranged in a crystal lattice
• Has a specific melting point under standard conditions
TB. pg 47
LIQUIDS• Particles move randomly but in a restricted fashion
• Smaller spaces between the particles than in gases
• Forces between the particles are weaker than in solids
• Diffusion occurs
• Collisions between the particles
• Fills the base of the container
• Takes on the shape of the bottom of the container
• Liquids exert pressure in all directions
• Has a specific boiling point and freezing point under standard conditions
TB. pg 47
GAS• Particles move randomly and quickly
• Huge open spaces between the particles
• Weak or negligible forces between particles
• Diffusion occurs and it is faster than in liquids
• More intense collisions occur between particles than in liquids
• Is compressible
• Gas exerts pressure in all directions
• Has a specific condensation point under standard circumstances
TB. pg 47
STATE CHANGE
WHAT IS THIS?
TB. pg 47
The possible state changes are:
1.Melting
2.Evaporating
3.Condensing
4.Freezing
5.Crystallizing
6.SublimationTB. pg 47
• Melting point: The temperature at which a solid completely changes into a liquid.
• Freezing point: The temperature at which a liquid completely changes into a solid.
• Boiling point: The temperature of a liquid at which the pressure of the vapour inside the bubbles (vapour pressure) is equal to the surrounding atmospheric pressure.
TB. pg 47
• The chemical composition stays the same
• Particle size
• Particle Shape
• Number of particles
During a phase changeThe physical properties change
Forces between particles are
weakened or broken.
In molecular substances – weak
intermolecular forces broken first –
requires small amounts of energy
• More organised structure = greater
forces between particles
• Less organised structure = less force
between particles
TB. pg 47+49
INTERMOLECULAR
FORCES
INTRAMOLECULAR
FORCES
H
H
HH
O
O• Requires a lot more
energy
• Strong forces• Requires little energy
• Van de Waals forces
• No chemical bonds made
• Can be reversed
Phase change
TB. pg 48
Looking inside molecules during a
STATE CHANGE
TB. pg 49
During condensation…
• Speed of particles: Slow down
• Spaces: Decrease
• Collisions: Less intense
• Forces: Stronger
• Arrangement: Still random
TB. pg 49
During Freezing…
• Speed of particles: Slow down
even more
• Spaces: Decrease (almost touch)
• Collisions: Vibrate
• Forces:Very strong
• Arrangement: Orderly
TB. pg 49
During Melting…
• Speed of particles: Speed up
• Spaces: Increase
• Collisions: Increase
• Forces: Weaker
• Arrangement: Less orderly
TB. pg 49
During Evaporation…
• Speed of particles: Extremely fast
• Spaces: Large (far apart)
• Collisions: Severe (high velocity)
• Forces: Very weak
• Arrangement: Random
TB. pg 49
Energy changes during a
STATE CHANGE
TB. pg 49
• It’s a Solid• fixed positions: vibrate (forces of attraction and
repulsion)
• heated: vibrate more energetically = increases
average kinetic energy = temperature rises
• doesn’t change phase yet:
• Has “kinetic and potential energy”
TB. pg 49
• It’s still a solid • Heated to a temperature at which melting begins –
further heat transfer does not increase kinetic
energy but potential energy.
• Lattice is now breaking apart into liquid phase –
particle more free to move
• Only when ALL have broken free – heat makes
kinetic energy increase and temperature now
increases
TB. pg 49
• Now it’s a liquid• When liquids temperature reaches boiling point –
temperature remains constant until all liquid bonds
broken and all has been changed into vapour.
• Heat added during boiling – increases potential
energy
• Usually takes more energy to vaporise than to
melt….WHY?
TB. pg 49
the heating / cooling curve
Represents phase change on a graph
If read from left to right: HEATING CURVE
If read from right
to left: COOLING
CURVE
DRAW THISEXPLANATION PG. 50
TIME (s)
To remember:During a phase change:
- Average kinetic energy remains the same
- Speed does not change
- Temperature remains constant
- Energy is used to break bonds between
particles from existing structure rather than to
make them move faster.
Potential energy
increases.
0
5
10
15
20
25
30
35
40
TB. pg 50
CLASS
ACTIVITY
1.1 What will the phase be of substance X at room temperature? (1)
1.2 What is the boiling point of substance X? (1)
1.3 Substance X was heated for 27 minutes. Why does the temperature
between time 4 – 8 minutes stay constant although heat was added? (2)
1.4 What happens to the particles of substance X between 0 – 4 minutes? (1)
1.5 At what stage (I, II, III, IV and V) will the particles have the most energy?
Give a reason for your answer. (3)
1.6 Is the substance Water? Why or why not? (2)
[10]
• 1.1 Liquid √ (1)
• 1.2 55°C √ (1)
• 1.3 Energy that is added is used to break particles out of their existing structure / state √ and not to make the particles vibrate / move faster √ (2)
• 1.4 The particles are in a solid state and as energy is added the particles start vibrating more until they are able to “break” out of the solid structure and form a liquid. √ (1)
• 1.5 V √ Highest temperature √ indicates highest kinetic energy √ (3)
• ONLY 1 mark if say: particles are in the gaseous phase.
• 1.6 NO √ - Water boils at 100°C and not 55°C √ (2)
: Heating and
Cooling curves
Determining the state of a substances by looking at melting
and boiling points
M BSOLID LIQUID GAS
Eg. Water 0 ºC 100 ºC
ice Water vapour
Which state is water at:
78℃?-8℃?
10℃?
10𝟏℃?
TB. pg 51
Practice: Use the table on page 51
According to the melting and boiling points in the table,
determine the state of the following compounds:
1.HF at 0℃?
2. Chlorine at -100℃?
3. Ammonia at -24℃?
4. HBr at -66℃?
TB. pg 51
HomeworkExercise 3 pg. 52-53Exercise 4 pg. 57-60
TB. pg 53-60
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