Term 2: Matter and Materials Grade 6 (NST)

Introduction
Solids, liquids and gases are the three main states of matter. Materials and substances are made
of matter. Matter is made of particles. The way the particles are arranged makes the matter a
solid, a liquid or a gas. Matter is made of very small particles.

A particle is the smallest part of a substance.

Particles move. Particles move all the time. Sometimes they move slowly, sometimes they move
fast. The speed and distance they move in determines if the material or substance is a solid, a
liquid or a gas.

Solids
When matter is solid, it has a fixed shape. The particles of solids are packed closely together.
There is very little space between the particles. The particles vibrate or move in one place. Eg.
Coin.

Liquids
Matter in the liquid state is able to flow. The substance will take on the shape of the container it is
in. The particles are packed close together, but they have no fixed shape. There are small spaces
between the particles. The particles can move around each other.

Gas
When matter is in the gas state, it fills the available space around it. The particles in gas are far
apart from each other and move fast. There is a lot of space between the particles. The particles
move in all directions.

Mixture: Mixtures of Materials

When two or more different substances (or materials) are combined, the result is a mixture. The
substances or materials can be in the solid, liquid or gas state.

Separating Mixtures
There are many different ways to separate mixtures so that the materials are visible again. It is
easier to separate substances we can see. We can physically separate these substances by
sieving, filtering, hand sorting, settling or decanting.

Method 1: Sorting by hand

Pouring the mixture onto newspaper or a piece of plastic
Using your fingers or a pair of tweezers
Picking out one of the materials from the others

Method 2: Using a sieve

Pouring the mixture through a sieve into a bowl
Shaking the sieve so that the small materials fall through
The larger material will remain in the sieve.

Method 3: Settling and decanting

Stirring the mixture
Leaving the mixture in its container
Allowing the mixture to stand until the two materials separate
Carefully pouring off the top material from the other material
Method 4: Filtering
Placing a funnel in a bottle
Placing filter paper in the funnel
Pouring the mixture through the funnel
Allowing the liquid material to flow through the filter

Solutions as Special Mixtures: Solutions

A solution is a special mixture of a liquid and a solid. Solutions are uniform in appearance

Dissolving a solid
Dissolving is the process of mixing a solid and a liquid so that the solid is no longer visible. If the
solid dissolves in the liquid, it is said to be soluble. If it does not dissolve, it is insoluble.

Dissolving uses mixing to combine a solid and a liquid.

Melting uses heat to convert one solid into a liquid.

Dissolving a solid: Solutes and Solvent

Solids that can dissolve are called solutes. The liquid in which a solute dissolves is called the
solvent. Water is a unique solvent as so many substances can dissolve in it.

The making of Sea Salt

Salt from the land has washed into the sea. The salt has dissolved in the sea and tastes salty. The
seawater is the solvent. The salt is the solute. The solution is the mixture of the salt and water.

Solutions as Special Mixtures: Saturated Solutions

When substances dissolve, solute particles become dispersed in the spaces between the solvent
particles. When the spaces are full, there is nowhere else for the solute to go. The solute particles
that are left out can be seen in the solvent.
Saturated – when a solution has no more space for any more particles of the solute.

Solutions as Special Mixtures: Insoluble Substances

Water is known as a universal solvent. Many different substances can dissolve in water and
makes water very useful. Substances that do not dissolve in water are insoluble. Oil is insoluble in
water. Oil and water do not mix and oil will float on water.

Insoluble Substances as Water Pollution

Oil and sand are only two of many substances that are insoluble in water. Waste such as plastic
bags, tins and bottles are all insoluble. They pollute our rivers and seas.

Dissolving: Rates of Dissolving

The speed at which a solute dissolves is called the rate of dissolving

There are three factors that affect the rate of dissolving:

Temperature of mixtures
Substances will dissolve faster in warmer water than in colder water. In warm water, there are
more spaces between the particles of water.

Stirring versus shaking the mixture

Stirring and shaking are both ways of mixing a solute with a solvent. Stirring is better at mixing the
solute with the solvent than shaking the solution.
Grain size of the solute
A large grain of solute will take longer to dissolve than a small grain. The larger the grain, the
slower the rate of dissolving will be.

Mixtures and Water Resources: Water Pollution

All water eventually runs into a river somewhere. If it is polluted water, it will carry the pollution to
the river. When pollution mixes with water it can dissolve and form a solution of solutes and
solvents which is poisonous to organisms in the water. Some pollution is insoluble but still mixes
with the water but is seen on the surface.

Insoluble Substances
Insoluble substances cannot dissolve in water and are harmless. Things like oil, plastic, tyres, tins,
glass and sewage waste are bad for the water and people using the water.

Oil Pollution
Oil can also pollute large amounts of water. Oil spreads as a thin layer on top of water. The oil kills
wildlife and plants that depend on the river. Oils make the water undrinkable and it is impossible to
remove.

Preventing Water Pollution

 Never throw waste into a river or on the ground.
 Never pour oil down a drain sink.
 Most insoluble items can be removed from a river by hand.
 Organised river clean-ups can remove many insoluble pollutants from our rivers.

Soluble Substances
Soluble substances dissolve in water. This means it is very difficult to know if they are in water or
not. They are virtually impossible to remove and cause pollution, which then makes the water
undrinkable.

Examples of soluble pollution are:

 Fertilisers and insecticides used by farmers
 Chemicals used by factories
 Soap powder used for washing clothes
 Soap used by people to wash themselves

Impact of Fertilisers on Rivers

The effect of these pollutants is to poison the water so that nothing can live in it we call this
eutrophication. Eutrophication is when small plants called algae feed of the fertilisers, soaps and
even some chemicals. The algae grow very fast and turn the rivers and lakes green. The water
cannot be used for drinking. Some algae secrete poisons that make the water poisonous.

Preventing Water Pollution:

 Use as little soap and detergents as possible.
 Use as little fertiliser as possible in your garden.
 Avoid using pesticides and herbicides in the garden.
Living Germs
Germs are living creatures that cannot be seen with the naked eye. Even clean looking water can
have germs. Germs cause diseases and cause people to become ill. The most common illness
carried by water is diarrhoea. The sewage from people is washed into rivers. People drink the
water and become ill. This forms a cycle of infection.
To avoid contracting diseases that are transported in water…
 Do not play in or drink polluted water
 Wash your hands with soap before eating
 Report broken toilets

Mixtures and Water Resources: Importance of Wetlands

A wetland is shallow body of water with plants such as reeds. Other names for wetlands are
marshes, swamps, seepage areas and food-plains. The water in a wetland can be salty or fresh
water. The slow flowing water allows insoluble substances to settle. Sand and silt sink to the
bottom of the wetland. The water becomes clear. Plants absorb nutrients from the water. Water
may become drinkable after flowing through a wetland.

Process to Purify Water: Clean Water

Animals and water
All animals would eventually dehydrate without water. Not only does water keep an animal cool
but water is also needed to digest food and remove waste. Without clean water, people would also
not be able to grow food, keep clean or be healthy.

Plants and Water

Plants need the nutrients that are dissolved in water. The waste contains nutrients that the plants
can use. The plants absorb the nutrients through their roots and the nutrients are used to make
food for the plants.

The Importance of clean water

Water management is everyone’s responsibility but the municipality officials of towns and cities
have the responsibility of looking after the water treatment facilities. The municipality must purify
water to keep people healthy.
M 2022
How a water treatment facility works
Water treatment plants are places where water from dams, rivers and aquifers are cleaned. To
clean the water the following steps are taken:
 Water is pumped to the water treatment plant.
 Water is filtered through a sieve.
 Water is then filtered through a very fine material called a membrane.
 A chemical called chlorine is added to kill any germs.
 Other chemicals are added to remove any bad tastes or smells.
 The water is pumped to factories and houses.
There are four ways to purify water:
Boiling Water
Boiled water is heated to kill any germs in the water.

Filtering Water
Pouring water through a funnel and filter paper removes most of the insoluble pollution.

Settling Water
Water that is allowed to settle will appear to be clean but not all the insoluble pollutants will settle.

Chemical Treatment
Chemicals or iodine added to water to kill germs but they are expensive and water taste awful.