CHAPTER FOUR: MATTER  
Concept of matter  
Matter is anything that has mass (weight) and occupies space. Example: stones,  
vegetation, air, food, water and animal bodies.  
Matter is everything that is found within our environment such as stones, vegetation,  
air, food, water and our bodies.  
Mass is a measure of quantity of matter in an object. It is measured in kilogram (kg)  
or grams (g).  
States of matter  
There are four fundamental states of matter which are;  
(i) Solid  
(ii) Liquid  
(iii) Gas  
(iv) Plasma  
•
The solid, liquid and gas states are  
composed of particles called atoms  
while plasma state is composed of  
charged particles.  
•
The liquid, gases and plasma are  
classified as fluids because their  
particles have ability to flow due to  
their constant random motion.  
Solids  
Solid is a substance that has definite shape and size. Solid also has definite volume. It  
is usually hard and not easily deformed. Example; stone, wood, sugar, sand, paper,  
iron, table, charcoal, cooking pot and pencil.  
Liquids  
Liquid is a substance which flows easily and has definite volume. A liquid takes the  
shape of the container holding it. Examples of liquids are water, kerosene, petrol,  
diesel, spirit (alcohol), milk, blood, juice, paints and oil.  
Gases  
Gases have no fixed shape or size. They flow easily and expand indefinitely to occupy  
the space in which they are held. Examples of gases are oxygen gas, hydrogen gas,  
carbon dioxide, water vapour, nitrogen gas, chlorine gas and ammonia gas.  
Plasma  
Plasma is a state of matter which occurs when a gas is extremely heated to form a  
mixture of positively charged ions and free electrons. Plasma is a charged gas that is  
less dense than solids or liquids and lacks the fixed shape and volume.  
Plasma occurs naturally in phenomena like  
(i) Stars and lightning  
(ii) Industrial processes  
(iii) Manufactured products like plasma televisions (TV’s)  
Lightning  
EXERCISE  
1. What are the conditions for a substance to be called matter?  
2. Why are liquids and gases categorized as fluids?  
3. Describe solids, liquids and gases in terms of shape and volume.  
4. Why do gases expand more than solids for the same increase in temperature?  
CHANGE IN STATES OF MATTER  
Matter may change its state from one form to another. This can be caused by change  
in temperature and pressure of matter. For example, when heated some solids melts  
to liquids, while liquids changes to gas (vapour) and vapour changes to plasma under  
high temperature due to ionization of vapour. An example of a substance which exists  
in all four states of matter is water.  
Processes involved in changes of states of matter  
(i) Melting and freezing  
Melting is a process in which a substance changes from a solid to liquid.  
When a solid is heated, the particles gain energy and vibrate fast and finally they  
break free from their fixed position and begin to move in clusters.  
Melting point is the temperature at which the solid changes to liquid at standard  
temperature and pressure.  
For example, melting point of ice (water) is 0oC. Substances with strong force of  
attraction between their particles have high melting points and the ones with weak  
force of attraction between particles have low melting point.  
Freezing is the process in which a substance changes from a liquid to a solid. It is  
associated with extremely cooling of liquids  
Freezing point is the temperature at which a liquid change to a solid.  
The freezing point of water is 0oC which is also the melting point of ice. Freezing  
point is slightly affected by change in atmospheric pressure of a place.  
(ii) Evaporation (vapourization)/ boiling and condensation  
Evaporation (vapourization) is the conversion of a substance from a liquid to a  
vapour. When a liquid is heated, the particles move faster as their average kinetic  
energy increases. Some of the particles at the surface of the liquid gain enough  
kinetic energy and escape into the air.  
Boiling is a change of state of matter from liquid to (gas) vapour state. The  
temperature at which the liquid starts to boil is called boiling point.  
Boiling point is the temperature at which the vapour pressure of the liquid is equal  
to the atmospheric pressure.  
Note:  
•
The boiling point describes how strongly the particles are held together in the  
liquid. Liquids with high boiling points have stronger forces of attraction between  
their particles than liquids with low boiling points.  
•
Boiling point of a liquid is affected by atmospheric pressure. Liquids have low  
boiling points at low pressure and high boiling points at high pressure. For example  
at low pressure water may vapourize even at room temperature, ie it boils at very  
low temperature.  
Differences between evaporation and boiling  
Evaporation  
Boiling  
(i) Occur at any temperature  
Occur at one particular  
temperature (boiling point).  
Occur both inside and on the  
surface of the liquid.  
Takes place faster  
(ii) Occur on the surface of liquid  
(iii) Takes place slowly  
(iv) Bubble are not necessary formed  
(v) Has cooling effect. I.e maintain body  
temperature and cool it when it get too hot.  
Bubbles are formed  
Has no cooling effect  
Condensation is the process of changing gas to liquid on cooling. During  
condensation, the particles lose kinetic energy and hence the force of attraction  
between particles becomes significant (operative).  
(iii) Sublimation and deposition  
Sublimation is a process of changing a solid directly into a gas without passing  
through liquid on heating.  
Deposition is the process of changing gases directly to solid without passing into  
liquid state on cooling.  
NB:  
In sublimation and deposition, the liquid state is bypassed.  
(iv) Ionization and deionization  
These processes are involved in the formation and deformation of plasma.  
Ionization is a process which occurs when neutral atoms lose electrons forming ions  
(charged particles). Ionization occurs when a gaseous state of matter is subjected to  
a very high temperature.  
Deionization is the recombination of free ions and electrons of the plasma to form  
atoms that finally combine to form gas molecules.  
OR  
Deionization is a process which occurs when the ions and free electrons in the  
plasma recombine to form neutral atoms or molecules.  
Deionization occurs when temperature is decreased leading to the free ions loosing  
kinetic energies.  
Kinetic energy is the energy possessed by an object because of its motion.  
SUMMARY ON THE CHANGES OF STATE OF MATTER FOR FOUR STATES  
SUMMARY ON THE CHANGES OF STATE OF MATTER FOR ONLY SOLID,  
LIQUID AND GAS  
OR  
EXERCISE  
1. Describe melting and freezing according to the states of matter  
2. Briefly explain the following terms:  
(a) Melting  
(b) Freezing  
(c) Boiling  
(d) Evaporation  
(e) Sublimation  
(f) Deposition  
3. Describe the differences between evaporation and boiling.  
4. Differentiate between sublimation and deposition.  
IMPORTANCE (SIGINIFICANCE) OF THE CHANGES IN STATES OF MATTER  
The following are the importance of change in state of matter in our daily lives:  
1. Water cycle  
Water cycle is the movement of water on, above and below the earth’s surface. In  
water cycle water changes from liquid to vapour by evaporation, from vapour to  
clouds by condensation and finally clouds to rain. Therefore, rain is formed mainly  
through evaporation and condensation  
2. Drying of materials  
Drying of materials occurs through evaporation whereby the liquid contained in the  
material changes to vapour. For example, drying of clothes and food stuffs such as  
vegetables, cassava and maize. Farmers in the village often spread crops on the  
ground to dry. Evaporation is also used to dry wet clothes suspended on a cloth line  
as a result of the heat produced by the sun.  
3. Refrigeration / air conditions  
Refrigerators use refrigerants which are chemicals whose change in state involves the  
change in energy. The change of state of refrigerants from liquid to vapour absorbs  
heat from the surroundings and thus causing the cooling. Air conditions work in the  
same way.  
4. Steam engines  
Steam engines use steam as working fluid to perform work. The change of state from  
liquid water to steam makes steam engines to operate. Steam engines were used in  
early trains and ships.  
5. Metallurgy (purification of metals)  
Metallurgy involves the extraction and purification of metals from their ores and the  
manufacture of alloys. The change of state from solid to liquid and from liquid to solid  
make metallurgy possible.  
6. Separation of mixtures  
Different mixtures can be separated by processes such as distillation, sublimation,  
evaporation and condensation. Example; A mixture of two or more substances with  
different boiling points e.g. water and alcohol can be separated by fractional  
distillation which involves evaporation and condensation.  
7. Refinery  
Petroleum refinery and distillery work under the principle that the liquids can change  
to vapour and then vapour can be cooled to liquids. While simple distillation is used in  
distilleries, fractional distillation is applied in petroleum refineries.  
8. Production of electricity  
Coal is used to heat water in closed system of pipes into vapour. The produced  
vapour is led by pipes to drive the turbines that in turn produce electricity.  
9. Cooling of our bodies in hot weather  
During hot weather, our bodies perspire a lot (undergo sweating). When water  
evaporates from the body, it takes up heat. This brings about the cooling effect, as  
heat is lost from the body surface.  
EXERCISE  
1. Explain the roles of temperature in the changes of states of matter  
2. Why do cold foods not smell from distance? Explain  
3. Provide real world examples of how the knowledge of changes in states of matter  
is applied in industries.  
PARTICULATE NATURE OF MATTER  
Matter is made up of particles. This was proved by the phenomenon known as  
Brownian motion which can be observed in liquids and gases.  
Brownian motion  
In 1827, a botanist called Robert Brown observed through a microscope that pollen  
grains suspended in water moved short distances in an irregular zigzag manner.  
This is because they are constantly bombarded by particles of water which cannot be  
seen even through a laboratory microscope. This shows that matter is particulate in  
nature.  
Brownian motion state that  
“
Matter is made up of tiny particle that are in a  
state of continuous random motion  
”
Other examples which show that matter is made up of particles that are in constant  
motion include:  
(a) The spread of the smell of the food being cooked from the kitchen to  
considerable distance,  
(b) Diffusion of potassium permanganate particles in water  
(c) The spread of perfume due to diffusion of perfume vapour into the air.  
Diffusion is the movement of particles from an area of high concentration to the  
area of low concentration.  
Question  
Fatuma placed a large crystal of potassium permanganate (VII) in the bottom of a  
beaker of cold water and left it for several hours.  
(a) Explain what she must have observed after five minutes. Explain  
(b) Describe what she likely observed after several hours. Explain  
(c) Name the two processes which have taken place  
(d) From that experiment give two conclusions about matter.  
ANSWER  
(a) After five minutes the colour of the solution become dark purple due to dissolution  
and diffusion of KMnO4 particles.  
(b) After several hours the colour of the solution may change to purple shade that is  
lighter than the initial colour. This is because the solution of water and KMnO4 is  
made up of very tiny particles which get dispersed and spread amongst  
themselves  
(c) The two processes which have taken place are dissolution, diffusion and  
dispersion.  
(d) From that experiment two conclusions that can be made are;  
•
•
Matter is made up of tiny particles  
Particles of matter are constantly moving.  
KINETIC NATURE OF MATTER  
The kinetic nature of matter refers to the idea that “All matter is made up of tiny  
particles called atoms and molecules that are in constant motion”.  
It explains the behaviour and properties of matter in terms of the motion of its  
particles which determines the properties of solids, liquids and gases.  
Key points of the kinetic nature of matter are  
(a) All matter is made up of tiny invisible particles (atoms and molecules)  
(b) The particles in matter are always in constant motion, i.e moving all the time.  
(c) The particles of matter are held together by force of attraction in which solids  
have strong electrostatic forces.  
(d) The movement of particles is due to kinetic energy which depends on  
Temperature.  
(e) Heavier particles move more slowly than lighter particles at the same  
temperature.  
(f) There are empty spaces between the particles of matter  
NB: The idea about the way particles behave in solids, liquid and gases is  
called kinetic molecular theory.  
BEHAVIOUR OF PARTICLES IN MATTER  
All matters are made up of small particles. The behaviour of these particles differs in  
the three states of matter. In solids particles are firmly packed, in liquid particles are  
close together while in gas particles are far apart from each other.  
Properties of Solids  
(a) Particles very closely (firmly) packed together  
(b) Has definite shape and volume  
(c) Has strongest inter-particle force  
(d) Particles are not free to move  
(e) Particles cannot be compressed.  
(f) Particles vibrate in fixed position.  
(g) Has high forces of attraction between the particles  
(h) It does not flow  
Properties of Liquids  
(a) Particles are close together  
(b) Have definite volume  
(c) Has medium density due to medium volume  
(d) Does not have definite shape, it takes the shape of the container  
(e) Molecules in a liquid can move in all direction with medium motion  
(f) Inter-particle force is weak  
(g) It can flow easily.  
(h) Particles in liquids cannot be compressed because are close together  
Properties of Gases  
(a) Particles are far apart from each other  
(b) Has no definite shape  
(c) Has no definite volume  
(d) Particles have largest distance from each other  
(e) Has low density due to largest volume  
(f) Has weakest inter particle force  
(g) Particle moves in all directions with high speed  
(h) The particles are randomly arranged.  
(i) It can flow easily.  
(j) Particles in gases can be compressed because are far apart.  
Properties of plasma state  
(a) Has no definite shape.  
(b) Has no definite volume, takes volume of its container.  
(c) Particles move freely like in gas and are highly energetic.  
(d) Particles can flow easily.  
Summary of the properties of matter  
Properties  
Shape  
Solid  
Liquid  
Gas  
Plasma  
Has fixed  
shape  
Takes shape of Has no definite Has no definite  
its container  
shape, fills the shape, fills the  
shape of the  
container  
shape of the  
container  
Volume  
Has a fixed  
volume  
Has a Fixed  
volume  
Takes volume  
Takes volume  
of its container of its container  
Movement  
of particles  
Particles do  
not move  
except  
Particles move Particles move Highly energetic  
or slide past  
one another  
randomly in all freely moving  
directions  
and regularly  
colliding  
vibrations  
particles  
Compressibility  
Generally  
Relatively  
Highly  
Highly  
incompressible incompressible compressible  
compressible  
Space  
No free space  
between  
particles  
Little free  
A lot of free  
A lot of free  
between  
particles  
space between space between space between  
particles  
particles  
particles  
Electrical  
Poor electrical  
conductivity,  
except for  
conductive  
solids like  
metals  
Some liquids  
can conduct  
Poor electrical  
conductivity  
High electrical  
conductivity  
because there  
are free  
conductivity  
electricity, but due to lack of  
generally lower free electrons  
than metals  
electrons  
present  
Flow  
Does not flow  
easily  
Flow easily  
Flow easily  
Flows easily  
PHYSICAL AND CHEMICAL CHANGES  
There are two major changes which are physical change and chemical changes;  
Physical change affects the physical properties of matter while chemical change  
affects both physical and chemical properties of matter  
PHYSICAL CHANGE  
Physical change is a change in which no new substance is formed.  
This is a temporary change which involves change in physical properties of matter  
such as colour and shape.  
Examples of physical changes include:  
(a) Melting of ice  
(c) Evaporation of water  
(e) Melting of candle wax  
(g) Crushing  
(b) Freezing of water  
(d) Dissolving salts in water  
(f) Magnetization of iron  
(h) Tearing  
(i) Condensation  
(j) Heating a metal (iron or wire) to red hot  
(k) Sublimation  
CHEMICAL CHANGE  
Chemical change is a change in which a new substance is formed. This is a  
permanent change which involves changes in chemical properties of a matter.  
Examples of chemical changes include:  
(a) Rusting of iron  
(b) Burning of piece of paper  
(d) Cooking of food  
(c) Souring of milk  
(e) Decaying of meat  
(g) Fermentation of fruits  
(f) Rotting of egg  
(h) Burning of candle.  
Differences between physical changes and chemical changes  
Physical change  
1. No new substance is formed.  
2. Are temporary changes.  
Chemical change  
A new substance is formed.  
Are permanent changes.  
3. The change is reversible  
(Return to original state).  
The change is irreversible (cannot be  
reversed).  
4. No energy is given out or absorbed. Energy is given out or absorbed.  
5. Affects only physical properties of  
Matter.  
Affect both physical and chemical  
properties of matter.  
6. There is no change in mass or  
weight of the substance.  
7. Molecules are rearranged while  
their actual compositions remain  
same.  
There is a change in the mass or  
weight of the substance.  
The molecular composition of a  
substance are completely changed.  
USES OF MATTER IN DAILY LIFE  
(a) Matter supports energy.  
(b) Matter used as food.  
(c) Matter helps to sustain our needs.  
(e) Matter helps in rain formation.  
(d) Matter helps in ecology and balance.  
(f) Matter is the basis of all nuclear reactions  
(g) Matter is the material required for starting chemical reactions.  
(h) Matter used in industries to make different products.  
(i) Matter helps in different studies. Pencil, books, pencils are materials for studies.  
EXERCISE  
1. When metals such as copper are heated, it expands. Explain what happens to the  
metal particles during expansion.  
2. Why do gases expand more than solids for the same increase in temperature?  
3. When a container of coffee is opened in a room, people in different parts of the  
room may notice its smell. Use kinetic theory of matter to explain how this  
happens.  
4. Using the idea of particles explain the following observations:  
(a) It is easy to pour a liquid  
(b) A gas will completely fill any container  
(c) A solid expands when it is heated  
5.  
(a) When you open a freezer you may find ice inside on the walls. How does this  
ice form? Explain  
(b) What would happen to a well stoppered bottle full of water left in a deep  
freezer over night? Explain