Teacher Pali’s IGCSE resources Chemistry (0625)- lesson based on specification and past
paper questions and key.
1: The particulate nature of matter
Matter is all the substances and materials that the universe is made from.
There are many millions of known chemical substances. All can be classified as solid, liquid or gas. They are
made of particles. As particles move they collide with each other and bounce off in all directions. This is
called random motion.
All types of matter are composed of tiny particles which are in constant motion; the physical properties of
matter are dependent on the movement of these constituent particles
Solids, Liquids and Gas properties
Properties Solid Liquid Gas
Bonds Strong intermolecular Relatively strong Very weak intermolecular
bonds intermolecular bonds; bonds
slightly weaker than those
of a solid
Fixed shape There is a fixed shape There is no fixed shape; There is no fixed shape;
liquids take the shape of gases take the shape of
their container their container
Fixed Volume There is a fixed volume Liquids have fixed volume Gases do not have a fixed
volume`
Arrangement of Particles are close Particles are close together Particles are far apart and
particles together and vibrate but not as close as solids bounce randomly around in
around a fixed point the container
Density Fixed and quite high Fixed and quite high Variable and quite low
Inter-particle Forces of attraction Forces of attraction Forces of attraction much
forces greater than average comparable to average less than average energy of
energy of particles energy of particles particles
Particle separation Particles held close Close but slightly separated Widely separated
together
Illustration
, Teacher Pali’s IGCSE resources Chemistry (0625)- lesson based on specification and past
paper questions and key.
Different states of matter in terms of kinetic particle theory
The smallest particle that cannot be broken down by chemical means is called an atom. In some substances,
particles are just single atoms. For example the gas argon, found in air, is made up of single argon atoms. ·In
many substances, particles chemically bonded together. These are called molecules. In other substances,
particles consist of atoms or groups of atoms that carry a charge. These particles are called ions.
The kinetic theory can be used as a scientific model to explain the different states of matter and the
interrelationship between them:
• Solids. The constituent particles are held close together by inter-particle attractive forces, the
particles have little freedom of movement and they can only vibrate around a fixed position
• Liquids. The constituent particles are held close together but the forces are weaker and the particles
have more freedom of movement. The particles have more energy and they move around in a
random manner, often colliding with one another.
• Gases. The forces of attraction between the constituent particles are so weak and their individual
energy is so high that forces of attraction become ineffective and the individual particles are free to
move around, restricted only by the walls of the container they are kept in. The particles move
randomly at very high speeds, colliding with each other and with the walls of the container in the
process.
, Teacher Pali’s IGCSE resources Chemistry (0625)- lesson based on specification and past
paper questions and key.
Interconversion of different states of matter in terms of kinetic particle
theory
The kinetic theory can be used to explain how a substance undergoes change from one state to another
If energy in the particles of a solid is increased (e.g. by heating), the attractive forces binding the particles
together are weakened. The particles are able to move around more freely. These results in a flexible shape
the solid shape gradually changes into a liquid one. The temperature at which this transition occurs from
solid to liquid is the melting point of the solid. The process gains heat energy so the process is endothermic.
If the liquid is further heated, the energy of the particles is increased even further. This causes faster
movement and the subsequent thinning of the liquid. A stage is reached when the particles at the surface
acquire enough energy to overcome the forces of attraction holding them together. They escape to form a
gas. The temperature at which this transition occurs from a liquid to gas is known as the boiling point. This
process gains energy so the process is endothermic.
The process of conversion from liquid → gas is called evaporation
The process of conversion from solid → gas is called sublimation
The process from solid → liquid → gas can be reversed by decreasing the temperature of the gas.
paper questions and key.
1: The particulate nature of matter
Matter is all the substances and materials that the universe is made from.
There are many millions of known chemical substances. All can be classified as solid, liquid or gas. They are
made of particles. As particles move they collide with each other and bounce off in all directions. This is
called random motion.
All types of matter are composed of tiny particles which are in constant motion; the physical properties of
matter are dependent on the movement of these constituent particles
Solids, Liquids and Gas properties
Properties Solid Liquid Gas
Bonds Strong intermolecular Relatively strong Very weak intermolecular
bonds intermolecular bonds; bonds
slightly weaker than those
of a solid
Fixed shape There is a fixed shape There is no fixed shape; There is no fixed shape;
liquids take the shape of gases take the shape of
their container their container
Fixed Volume There is a fixed volume Liquids have fixed volume Gases do not have a fixed
volume`
Arrangement of Particles are close Particles are close together Particles are far apart and
particles together and vibrate but not as close as solids bounce randomly around in
around a fixed point the container
Density Fixed and quite high Fixed and quite high Variable and quite low
Inter-particle Forces of attraction Forces of attraction Forces of attraction much
forces greater than average comparable to average less than average energy of
energy of particles energy of particles particles
Particle separation Particles held close Close but slightly separated Widely separated
together
Illustration
, Teacher Pali’s IGCSE resources Chemistry (0625)- lesson based on specification and past
paper questions and key.
Different states of matter in terms of kinetic particle theory
The smallest particle that cannot be broken down by chemical means is called an atom. In some substances,
particles are just single atoms. For example the gas argon, found in air, is made up of single argon atoms. ·In
many substances, particles chemically bonded together. These are called molecules. In other substances,
particles consist of atoms or groups of atoms that carry a charge. These particles are called ions.
The kinetic theory can be used as a scientific model to explain the different states of matter and the
interrelationship between them:
• Solids. The constituent particles are held close together by inter-particle attractive forces, the
particles have little freedom of movement and they can only vibrate around a fixed position
• Liquids. The constituent particles are held close together but the forces are weaker and the particles
have more freedom of movement. The particles have more energy and they move around in a
random manner, often colliding with one another.
• Gases. The forces of attraction between the constituent particles are so weak and their individual
energy is so high that forces of attraction become ineffective and the individual particles are free to
move around, restricted only by the walls of the container they are kept in. The particles move
randomly at very high speeds, colliding with each other and with the walls of the container in the
process.
, Teacher Pali’s IGCSE resources Chemistry (0625)- lesson based on specification and past
paper questions and key.
Interconversion of different states of matter in terms of kinetic particle
theory
The kinetic theory can be used to explain how a substance undergoes change from one state to another
If energy in the particles of a solid is increased (e.g. by heating), the attractive forces binding the particles
together are weakened. The particles are able to move around more freely. These results in a flexible shape
the solid shape gradually changes into a liquid one. The temperature at which this transition occurs from
solid to liquid is the melting point of the solid. The process gains heat energy so the process is endothermic.
If the liquid is further heated, the energy of the particles is increased even further. This causes faster
movement and the subsequent thinning of the liquid. A stage is reached when the particles at the surface
acquire enough energy to overcome the forces of attraction holding them together. They escape to form a
gas. The temperature at which this transition occurs from a liquid to gas is known as the boiling point. This
process gains energy so the process is endothermic.
The process of conversion from liquid → gas is called evaporation
The process of conversion from solid → gas is called sublimation
The process from solid → liquid → gas can be reversed by decreasing the temperature of the gas.
