Structure, bonding and properties of matter
Structure, bonding and properties of matter
Level: AS Levels, A Level, GCSE – Exam Boards: Edexcel, AQA, OCR, WJEC, IB, Eduqas – Chemistry Revision Notes
Structure, bonding and properties of matter
Exam Boards:
The three states of matter
The three states of matter are solid(s), liquid(l) and gas(g).
Note: An aqueous (aq) solution is formed when a substance is dissolved in water.
These states of matter can be represented using simple diagrams (models) where the particles can be represented by solid spheres.
. 
. 
Solid Liquid Gas
(Diagrams: Twinkle)
The particles in a solid: |
The particles in a liquid: |
The particles in a gas |
| · have a regular pattern
· vibrate in a fixed position · cannot flow · are tightly packed · have low kinetic energy · cannot be compressed (no space between particles)
|
· have a random arrangement
· are able to move around and slide over one another · can flow · take the shape of their container · have more kinetic energy than in a solid · cannot be compressed (not enough space between particles)
|
· have a random arrangement and are far apart
· can move around in all directions · can flow · fill the container they are in · can be compressed (particles have space between them to move into)
|
Limitations of the particle model:
- forces between spheres are not shown
- all particles are shown as spheres
- the spheres are shown to look solid and inelastic
- forces and collisions between particles cannot be represented
Changing States
For a substance to change state, energy must be transferred.
Diagram:
Heating a substance gives the particles more energy.
- Some of the attractive forces between particles are broken and the distance between particles increases.
- The arrangement of the particles becomes more random.
- Boiling takes place at the boiling point.
- Melting takes place at the melting point.
To evaporate or boil a liquid, energy is needed to overcome the intermolecular bonds between the particles.
Evaporation: particles leave the surface of the liquid.
Boiling: bubbles of gas form before rising to the surface and escaping.
Cooling a substance means particles move less so less energy is needed.
- The distance between particles decreases and their arrangement becomes less random.
- Freezing takes place at the melting point.
- Condensing takes place at the boiling point.
The amount of energy required for a change of state depends on the strength of the forces between particles. The stronger the forces of attraction, the more energy needed to break them apart.
Substances that have strong attractive forces between particles generally have higher melting and boiling points.
Identifying the state of a substance
- If the temperature is lower than the melting point, the state of the substance will be solid.
- If the temperature is between the melting point and boiling point, the substance will be a liquid.
- If the temperature is higher than the boiling point, the substance will be a gas.
Substance |
Melting Point (oC) |
Boiling Point (oC) |
State at room temp (21oC) |
| w | -18 | 42 | liquid |
| x | 145 | 870 | solid |
| y | -185 | -84 | gas |
| z | -56 | 16 | gas |
Question 1 (AQA)
The table below gives information about four alcohols.
| Alcohol | Formula | Melting point in °C |
Boiling point in °C |
| Methanol | CH3OH | −94 | 65 |
| Ethanol | CH3CH2OH | −118 | 78 |
| Propanol | CH3CH2CH2OH | −129 | 97 |
| Butanol | CH3CH2CH2CH2OH | −89 | 118 |
Which alcohol in the table is liquid over the greatest temperature range?
__________________________________
Answer: propanol
Question 2
What does the amount of energy required for a change of state depend on?