States of Matter

1. STATES OF MATTER

2. GASES
Gases have no fixed shape or volume. Gas particles:
■■ are far apart, therefore gases can be compressed
■■ are randomly arranged
■■ can move freely from place to place, in all directions.

3. LIQUID
Liquids take the shape of the container they occupy.
Liquid particles:
■■ are close together, so liquids have a fixed volume and can only be
compressed slightly
■■ are arranged fairly randomly
■■ have limited movement from place to place, in all directions.

4. SOLID
Solids have a fixed shape and volume. Solid particles:
■■ are touching each other, so solids cannot be compressed
■■ are usually in a regular arrangement
■■ cannot change positions with each other – they can only vibrate.

5. WHEN WE HEAT A SOLID:
■■ the energy transferred to the solid makes the particles vibrate
more vigorously
■■ the forces of attraction between the particles weaken
■■ the solid changes to a liquid when its temperature is sufficiently
high.
We call this change of state melting.

6. WHEN WE HEAT A LIQUID:
■■ the energy transferred to the liquid makes the particles move
faster
■■ the forces of attraction between the particles weaken
■■ the particles with most energy are the first to escape from the
forces holding them together in the liquid
■■ the liquid evaporates – this happens at a temperature below the
boiling point
■■ the forces weaken enough for all the particles to become
completely free from each other; they move fast and randomly and
they spread out
■■ the liquid boils; this happens at the boiling point.

7. WHEN WE COOL A VAPOUR, THE
PARTICLES:
■■ lose kinetic energy so the molecules move around less quickly
■■ experience increasing forces of attraction
■■ move more slowly and become closer together when the
temperature is sufficiently low; the gas liquefies.
We call this change of state condensation.

8. IONIC SOLID
■■ They are hard. It takes a lot of energy to scratch the surface because of the
strong attractive forces keeping the ions together.
■■ They are brittle. Ionic crystals may split apart when hit in the same direction
as the layers of ions. The layers of ions may be displaced by the force of the
blow so that ions with the same charge come together. The repulsions between
thousands of ions in the layers, all with the same charge, cause the crystal to
split along these cleavage planes.
■■ They have high melting points and high boiling points because the attraction
between the large numbers of oppositely charged ions in the lattice acts in all
directions and bonds them strongly together. The melting points and boiling
points increase with the charge density on the ions. So magnesium oxide,
Mg2+O2–, has a higher melting point (2852 °C) than sodium chloride, Na+Cl–
(801 °C). This is because there is a greater electrostatic attraction between
doubly charged ions than singly charged ions of similar size.
■■ Many of them are soluble in water.
■■ They only conduct electricity when molten or in solution

9. METALLIC LATTICE
We learnt that a metallic lattice consists of ions surrounded by a sea
of electrons. The ions are often packed in hexagonal layers or in a
cubic arrangement.
When a force is applied, the layers can slide over each other. But in a
metallic bond, the attractive forces between the metal ions and the
delocalised electrons act in all directions. So when the layers slide,
new metallic bonds are easily re-formed between ions in new lattice
positions and the delocalised electrons.
The delocalised electrons continue to hold the ions in the lattice
together. The metal now has a different shape. This explains why
metals are malleable (they can be hammered into different shapes)
and ductile (they can be drawn into wires). The high tensile strength
and hardness of most metals is also due to the strong attractive
forces between the metal ions and the delocalised electrons.

10. GRAPHITE
The properties of graphite are related to its structure.
■■ High melting and boiling points: there is strong covalent bonding
throughout the layers of carbon atoms. A lot of energy is needed to
overcome these strong bonds.
■■ Softness: graphite is easily scratched. The forces between the
layers of carbon atoms are weak. The layers of graphite can slide over
each other when a force is applied. The layers readily flake off. This
‘flakiness’ is why graphite is used in pencil ‘leads’ and feels slippery.
■■ Good conductor of electricity: when a voltage is applied, the
delocalize electrons (mobile electrons) can move along the layers.

11. DIAMOND
The properties of diamond are related to its structure.
■■ High melting and boiling points: there is strong covalent bonding
throughout the whole structure. A lot of energy is needed to break
these strong bonds and separate the atoms
■■ Hardness: diamond cannot be scratched easily because it is
difficult to break the three-dimensional network of strong covalent
bonds.
■■ Does not conduct electricity or heat: each of the four outer
electrons on every carbon atom is involved in covalent bonding. This
means that there are no free electrons available to carry the electric
current.

12. BUCKMINSTERFULLERENE

13. NANOTUBES
Nanotubes have characteristic properties:
■■ They have high electrical conductivity along the long axis of the
cylinder. This is because, like graphite, some of the electrons are
delocalised and are able to move along the cylinder when a voltage is
applied.
■■ They have a very high tensile strength when a force is applied
along the long axis of the cylinder. They can be up to 100 times
stronger than steel of the same thickness.
■■ They have very high melting points (typically about 3500 °C). This
is because there is strong covalent bonding throughout the structure.

14. GRAPHENE
Graphene has some of the properties of graphite, but they are more
exaggerated. For example:
■■ Graphene is the most chemically reactive form of carbon. Single
sheets of graphene burn at very low temperatures and are much more
reactive than graphite.
■■ Graphene is extremely strong for its mass.
■■ For a given amount of material, graphene conducts electricity and
heat much better than graphite.

15. CONSERVING MATERIALS
Why conserve materials?
Do a research to find the answer make the notes.

16. QUESTION 1
A. What do you understand by the term ideal gas?
B. Under what condition does a gas not behave ideally? Explain
C Helium is a noble gas . Explain why it has low boiling point and
does not conduct electricity
D. Weather balloon contains 0.500 kg of helium. Calculate the volume
of gas at a pressure of 0.500 * 10^5 pa at temp – 20 C

17. QUESTION 2

18. QUESTION 3

19. QUESTION 4

20. QUESTION 5