All objects around us are made of one or more materials.
Grouping is done on the basis of similarities or dissimilarities of materials.
The properties of materials are Appearance, Hardness, Solubility, Transparency, etc.
Some materials can be lustrous or non-lustrous in appearance.
Lustrous materials are diamond, freshly cut metals, gold foil, etc.
Some metals often lose their shine and appear dull, because of the action of air and moisture on them. We therefore, notice the lustre, only on their freshly cut surface.
Non-lustrous materials are wood, rusted iron, blackboard, etc.
Materials which can be compressed or scratched easily are called soft. For eg: cotton, sponge.
Materials which are difficult to compress are called hard. For eg: Wood, Stone.
In appearance, materials can have different properties, like lustre, hardness, be rough or smooth.
Some substances completely disappear or dissolve in water. They are known as soluble substances. Eg: Sugar, Salt.
Some substances do not mix with water and do not disappear even after we stir for a long time are known as insoluble substances. Eg: Chalk powder, Sand.
Some liquids mix with each other completely, are known as miscible liquids. Eg: Chocolate syrup with milk.
Some liquids do not mix with each other and form a separate layer, are known as immiscible liquids. Eg: Oil and water.
Water plays an important role in the functioning of our body because it can dissolve a large number of substances.
Those substances or materials, through which things can be seen clearly, are called transparent. Eg: Clean water, Plain glass.
Some materials through which you are not able to see. These materials are called opaque. Eg: Book, Wooden door.
The materials through which objects can be seen, but not clearly, are known as translucent. Eg: Coloured glass, Butter paper.
We often group materials for our convenience.
Dividing materials in groups makes it convenient to study their properties and also observe any patterns in these properties
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