Properties of matter – upper primary science

Bbosa Science 07/09/2020 15:22 1

PROPERTIES OF MATTER

Matter

Matter is anything that occupies space and has mass. Mass is what matter is made up of. Matter exists in three states commonly known as solids, liquids and gases.

Characteristics of matter

The different states of matter have different characteristics in regard to shape, volume and mass.

Solids have a definite shape, volume, and mass. Examples of solids are brick, sand, shoe
Liquids unlike solids have no definite They take the shape of the container they occupy. However, have definite volume and mass. Example of liquids are water, milk, petrol.
Gases like liquids have no definite They take the shape of the container they occupy. They have no definite volume and compressed. They however have mass.

Effects of heat on matter

Effects of heat on solids

When solids are heated the following things may take place:

expands or increase in size
melts or change into liquid
sublime or changes directly to gas without going through a liquid
on cooling the solid contraction .

Effects of heat on liquids

When the liquid is heated it evaporates into a gas. On cooling the gas condenses into a liquid or sublimes into a solid.

Summary of effect of heat no matter

Air

Air is a mixture of gases i.e.

nitrogen 78%
oxygen 21%
inert gases 0.97%
carbon dioxide 0.03%
Note that air contains certain varying amounts of water and dust particles.

Component of air	Used for
Oxygen	Breathing, burning, rusting and germination
Carbon dioxide	Photosynthesis (Making plant food), preserving soft drinks, putting out fire (fire extinguishers),
Nitrogen	Used by legumes to fix nitrogen into the soil
Inert gases	Used in electric bulbs or tube

Wind

This is moving air

Effects of moving air (wind)

Wind as negative effects on our surroundings particularly when it is very strong. Some effects of winds are:

blowing soil away (erosion)
blowing roofs away
felling trees

Uses of moving air (wind)

We normally make use of wind in many ways. Some uses of wind are:

Winnowing – this is the process of separating chaff from grains by using the The grains are tossed in the air and if the wind is blowing the chaff are blown away by the wind leaving the grains. One can also blow
away the chaff using the mouth.
Sailing boats and canoes –some boats and canoes have sail (a large piece of very strong cloth) that they use to catch the wind in order for the boat or canoe to move forward,
Turning windmills – a windmill is a structure that has blades attached to its roof and is driven by the wind
in order to turn and drive a machine attached to it. A wind mill can be used to generate electricity.

Experiment to show that air occupies space

When air is blown into a balloon, the balloon expands.
When the glass is inverted in a basin of water, the water does not enter the glass because air occupies space in glass

3. Air bubbles out of an empty jerry can or bottle before water enters.

Experiment to show that air has weight.

A deflated balloon is lighter than a balloon that contain air

Experiment to show that air exerts pressures

Density of substance

Density is mass / volume

Mass is object is determined by weighing balance

Volumes of regular objects can be determined from the formulas

Volumes of irregular objects

Volume using displacement method

Using overflow can

Example

Find the density of acube of side of 2cm³ and mass of 10g

Volume = l x w x h = 2 x 2 x 2 = 8cm³

Density = mass/volume = 10/8 =1.25gcm^-3

Note that the density of water = 1gcm^-3 or 1000kg/m³

Floating and sinking in a liquid

A substance denser than a liquid sinks while that less dense than a liquid float,

A substance that sinks displaces amount of a liquid equal to its volume.

A substance that float displace amount of a liquid equal to its weight.

For example stones, metals sink in water because it is denser than water while paraffin floats in water because it is lighter than water.

Pressure in liquids

The force that makes the liquid to flow is called pressure. The refusal of the difficult of a liquid to flow is viscosity. Pressure in liquids increase with depth as shown in the diagram below

Pressure increases with depth

The diagram shows that the jet at the bottom of the container (3) has more pressure than all the others. This is because it is the deepest among the others. Therefore the pressure increases with depth.

Mixtures

A mixture is a combination of two are more mixture

Examples

Solid mixture such as maize and bean
Suspension is made of insoluble solid powder in a liquid
Solution is made of a two miscible liquids such a petro and paraffin or a soluble solid in a liquid such as sugar in water. The liquid that dissolves a solid is called a solvent while a solid that dissolves in a liquid is a solute

Methods of separating mixtures

Winnowing – the wind is used to separate chaff, small sticks, and dry leaves, from grains or seeds by blowing the chaff away. Chaff are usually lighter than the grains.
Sieving – a sieve is used to separate mixtures of particles of different For example stones from flour. The larger particles remain on the sieve while the finer ones pass through.
Picking /sorting– Here the large particles are separated from smaller ones by observing them and using the hands to remove the unwanted ones. For example stones are separated from rice or beans in this way.
Filtering- this method is used to separate a liquid from particles that cannot dissolve in it. For example separating sand from water using filter paper or piece of cloth.
Decanting – this is when a liquid is separated from large particles of solids by pouring the liquid out For example pouring off kerosene that has mixed with tiny ball bearings.
Using a magnet – a magnet is used to separate magnetic materials that may have mixed up with powder or other non-magnetic materials. For example a magnet is used to separate iron fillings from sugar.
Evaporation- a solid that has dissolved in a liquid is separated in this The liquid is heated until it evaporates and the solid is left behind, For example salt dissolved in water can be recovered by evaporation.
Miscible liquids are separated by a separating funnel

Physical and chemical changes

A physical change: Is one in which no new substance is formed.

Examples of physical change are

Melting of wax
Melting of ice
Boling of water
Expansion of metal
Evaporation
Sublimation of iodine, ammonium chloride, iron (III) chloride

A chemical change:

Is one in which a new substance is formed.

In many chemical changes, heat and light are given out.

In a chemical change, it is difficult or impossible to change the new substance back to their original composition.

Examples of chemical changes

Burning of candle wax

It requires oxygen to take place

Rusting

Rusting

When iron is left in damp air for some time it become covered with a brown coat called rust. Chemically rust is hydrated iron III oxide Fe₂O₃.xH₂O.

Disadvantage of rusting

Weaken objects made of iron
Makes objects made of iron look ugly

Conditions necessary for rusting

Oxygen not air
Water

Experiment to show that oxygen and water is necessary for rusting

The experiment is set up as shown above and left for several days

Test tube A contains nails and moist air
Test tube B contains nails and dry air because moisture is removed by anhydrous calcium chloride
Test tube C contains nail and air free water; boiling removes dissolved air from water while a layer of oil prevents entry of air into water

Observation after several days

In test tube a rusting took place because there is both oxygen and water necessary for rusting to take place.
In test tube B rusting did not take place because there was not water
In test tube C rusting did not take place due to absence of air

Conclusion

Both oxygen and water are necessary for rusting to take place

Method of preventing rusting

Keeping iron and steel equipment in air or water free environment, i.e., in the dry places (from water).
Oiling (protects equipment from water and oxygen).
Painting (protects from both air and water)
Tin plating protects iron from both air and water; however, tin-plate is only effective provided the layer of tin remains intact
Galvanizing: this is coating iron with zinc. Zinc protects iron because it is passive in air but also it can reduce iron III to ion.
Alloying

An alloy is a mixture of two or more metals

Examples of alloys

Alloy	Composition	uses
Steel	Iron and carbon	Making cooking utensils, bridges
Bronze	Copper and tin	Ornaments, coins
Brass	Copper and zinc	Coins, ornament
Solder	Tin and lead	Welding

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