[Short Notes] NCERT Class VI – Sorting Materials into Groups – Chapter 4
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All objects around us are made of one or more materials.
These materials may be made up of glass, metal, plastics, wood, cotton, paper , mud , soil.
An object could be made up of different materials & One material can be used to make many different objects.
Materials usually look different from each other. At the same time there may be some similarities between them.
Cut each material into pieces and look at the freshly cut pieces or rub the surface of material with a sand paper & you can see its lustre.
Materials which have lustre are usually metals.
Example: Iron , Copper, Gold
Some metals often lose their shine & appear dull because of the action of air & moisture. So we can see lustre only on their freshly cut surface.
While pressing different materials, we can feel that some materials are Hard to compress and some are easily compressible.
Materials which can be compressed or scratched easily are called soft while some other materials which are difficult to compress are called hard.
For example, cotton or sponge is soft while iron is hard.
Soluble or Insoluble
When some materials are added to water and stirred, we find that it completely disappears. these
substances are soluble in water.
Other substances do not mix with water and do not disappear even after stirring for a long time. long time. These substances are insoluble in water.
Water plays an important role in the functioning of our body because it can dissolve a large number of substances.
Some gases are soluble in water whereas others are not. Water, usually, has small quantities of some gases dissolved in it. For example, oxygen gas dissolved in water is very important for the survival of animals and plants that live in water.
Those substances or materials, through which things can be seen, are called transparent.
Glass, water, air and some plastics are examples of transparent materials.
There are some materials through which you are not able to see. These materials are called opaque.
Wood, cardboard and metals, are examples of opaque materials.
The materials, through which objects can be seen, but not clearly, are known as translucent.
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