Material and Their Properties
Everything that we see around us is made up of material. Material is the substance or substances of which a thing is made or composed such as metal, wood, plastics, glass and fabrics. Each material is made up matter, matter is a physical substance which occupies space and has some weight.
Physical Properties of Matter
The properties of matter refer to the qualities/attributes that distinguish one sample of matter from another.
Look – How do you recognize anything? We usually see its size, shape, position and feature to recognize a particular thing.
Feel – Touch an iron rod, a piece of paper and a plastic bag. What do you observe? Do they feel different? Yes, object made of different material feel different.
Smell – Smell hair oil, cooking oil and kerosene. Do they smell same? No, each of these has a unique smell, which helps us to distinguish them.
Taste – Every material differ in taste. Example: sugar tastes sweet, salt taste salty, lemon taste sour. We must be careful while tasting anything as it could poisonous such as lead, mercury etc.
Density- We may have observed that things of same size have different weights, like feather, a sponge or a wood. This is because the material out of which the object is made, are packed more densely or closely than other.
Solubility – It describes how well a substance dissolves in another substance. Solubility is a measure of how easily the substance dissolves in water.
Experiment: Measuring the solubility of different substances
Take a piece of wood, 1 spoon of salt and 1 spoon of sugar in three different containers. Pour water in all the three containers. Stir them.
Which of these dissolve more easily in water?
Salt dissolves more quickly.
Materials that dissolve in water are called soluble substances. Example: sugar, salt, milk powder etc. Materials that do not dissolve in water are called insoluble substances. Example: wood, stone etc.
What is matter made of?
Matter is made up of tiny particles called molecules. Molecule is a group of atoms bonded together. Atoms are so small, that they cannot be seen by naked eye. The molecules of every substance are different from the molecules of any other substance.
Observe a tiny grain of a sugar and a salt using a magnifying glass. You will find that sugar crystal is very different from salt.
Three states of matter
Matter can exist in one of three main states: solid, liquid, or gas.
Solid – Material that retains its shape and volume is called solid. Example: building, stone, tin box etc.
A solid's particles are packed closely together. Particles cannot move freely; they can only vibrate. As a result, a solid has a stable, definite shape and a definite volume.
Liquid – Material that does not retain its fixed shape is called liquid. Liquid matter is made of more loosely packed particles. It will take the shape of its container. Particles can move about within a liquid, but they are packed densely enough that volume is maintained.
Pour equal amount of liquid into containers of different sizes. What do you observe?
Liquid can be poured as it has flow and take the shape of container. It takes up space, has weight and has fixed volume.
Gas – Our atmosphere contains a large mixture of gases, which occupy much of the space around the globe. Gaseous matter is composed of particles packed so loosely that it has neither a defined shape nor a defined volume. It assumes the shape and volume of its container. Gas can flow and expands to fill all the space available to it. A gas can be compressed. When gas is compressed, its molecules have to huddle together. Pretty soon they're bonding to form a liquid. Further compression will lock them together tightly to make a solid.
When a sample of matter in the gaseous state is heated, the atoms or molecules gain energy and move more rapidly. When a sample of gaseous matter is cooled, the atoms or molecules lose energy and move more slowly.
Experiment: Try to lift a cylinder filled with gas and then lift an empty cylinder at home. What do you observe? It is difficult to lift a cylinder filled with gas than an empty cylinder. This shows gas has weight.
Change in state of matter
Matter changes its form under certain conditions, like heating or cooling.
When we take out ice cubes from freezer, they are hard and solid. After a few minutes, it starts melting and turns into a liquid. Why is it so?
Matter changes its state from solid to liquid or to a gas because of the change in their molecules. Heating can change solids into liquids or gases. On heating temperature rises and molecules absorb heat to become freer and move apart. Most solids melt into liquid when they are heated.
When we boil water in a kettle it changes to vapor. Why is it so?
This happen because water molecules in the kettle become restless on heating and move further apart and comes out from the spout in the form of vapor. Liquid evaporates into a gas when it is heated.
On freezing water (liquid), it changes to ice (solid). Why is it so?
On freezing water molecules give up their heat and settle closer together. Thus liquid water becomes solid and hard. A liquid freezes into a solid when it is cooled and a gas condenses into a liquid when it is cooled.
These changes from one substance to another are called changes in state of matter.
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