IGCSE Chemistry
1 The particulate nature of matter
1 Demonstrate understanding of the terms atom and molecule.
atom –
element –
molecule –
compound –
particle – any small piece of a substance; it could be a molecule or billions of
molecules
mixture –
solute –
solvent –
solution –
solution –
filtrate –
residue –
saturated solution –
concentration –
colorless –
purity -
4.1 States of matter
State the distinguishing properties of solids, liquids and gases.
4.2 Molecular model
Describe qualitatively the molecular structure of solids, liquids and
gases.
Relate the properties of solids, liquids and gases to the forces and
distances between molecules and to the motion of the
molecules.
solid
liquid
gas
description
fixed volume,
own shape
fixed volume,
takes shape of
container
any volume takes
shape of
container
arrangement of
particles
in a regular patter
called a lattice
random
random
separation of
particles
close together,
touching
movement of
particles
vibration around
a fixed position
attractive forces
between particles
stronger than the
liquid phase
still close
together, just
slightly farther
apart than those
in the solid phase
slow movement
in a random way
from place to
place, sliding past
each other
slightly weaker
than the solid
phase
separated, far
apart
fast random
movement
no attractive
forces between
particles
When the temperature of a solid increases, so does the energy of the
particles.
At the melting point the particles have enough energy to move past each
other and change positions.
Liquids can flow and change their shape.
When a liquid is heated, the energy of the particles increases.
At the boiling point the intermolecular forces can no longer hold the
particles together, so the particles separate & become a vapor or gas.
The particles can change position and move apart.
Gases can flow and expand to fill any space.
supply heat
energy
solid
supply heat
energy
liquid
heat energy
given to
surroundings
gas
heat energy
given to
surroundings
Interpret the temperature of a gas in terms of the motion of its
molecules.
The higher the temperature, the faster the speed of the molecules.
Temperature is a measure of the average speed of the molecules.
Temperature is how hot something is; heat is energy that flows from hot
substances to cold substances.
Describe qualitatively the effect of a change of temperature on the
pressure of a gas at constant volume.
The higher the temperature, the larger the volume of gas at a constant
pressure.
Describe qualitatively the pressure of a gas in terms of the motion
of its molecules.
At a constant temperature, gas molecules move at a constant average speed,
so that the force of the collision is the same ( on average ).
If the gas is compressed into a smaller volume, there are more frequent
collisions on each unit of area, so that the total force per unit area
increases and the pressure increases.
If a gas expands to a greater volume at a constant temperature, the pressure
decreases.