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

Write this

down

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