NCERT Class- 6 Science Chapter- 4 Notes

Objects around us

There is a lot of variety in our food and clothes. Everywhere there are many things of different types from it.
We see in our four orders chairs, bullock carts, cycles, cooking utensils, books, clothes, toys, water, stones, and many other things. The shapes, colors, and guns of all these objects are different.
The things around us are made up of one or more substances. It is made of materials. These materials can be glass, metals, plastics, wood, cotton, paper, mud, and dead.
Sometimes an object is made of only one substance, then it also happens that one thing can be made of many things by using many things.

If we make a glass of cloth, it will not prove to be proper. To make glass, we need glass, plastic, metal, or any such material which can hold water.
Similarly, using paper for making cooking utensils will also not be considered a wise act. Then we see that the choice of material by us to make an object depends on the properties of that material and the purpose of the object to be used.

Substances often appear different from each other. Wood looks completely different from iron. Appears to be different from iron, copper, or aluminum. But still iron, copper, and aluminum can have some similarities, that wood cannot have.
Instead of cutting, you can rub the surfaces of the materials with sand to see if they are useful or not.
Substances in which this type of dust is present. Some metals often lose their luster and appear neutral. This is due to the reactions of moisture on them. Therefore, we should try to look only at the freshly cut pages and see whether they are free or not.

When we press different substances with our hands, some of them are difficult to press, while others are easily compressed.
Take a metal key and try to scratch the surfaces of wood, aluminum, stone, nail, candle chuck, and many other objects or objects with it. You can do some easy and it will not be so easy to do some.
Those substances which are difficult to compress easily are called hard materials.
Those which are easily scratched are called soft materials.

An object can float in water, so there are some things that can sink in water.
Whatever object is light in weight, that object can float easily in water, some smooth objects like oil can also float in water.
Objects floating in water- dry grass, dry leaves, dry wood, balls, mustard oil, hair, foil, etc.
Anything that is heavy in weight cannot float in water.
Objects that can be submerged in water – Pebble, iron nails, marble, piece of stone, steel spoons, keys, sticks, coconut, fruit, etc.

The substances or materials through which objects can be seen are called transparent. Glass, air, and some plastics are examples of transparent materials.
Often shopkeepers like to keep other food items like biscuits, sweets, toffee, etc. in transparent glass or plastic sheets.
On the contrary, there are some substances through which you cannot see things. These substances are called opaque.
You cannot tell what is kept inside a closed wooden box, what is inside a steel bottle, or what is inside a black foil, all these are examples of opaque materials.

If you can see through, then that object allows light to pass through it. Such an object is called transparent and the substance through which objects can be seen but cannot be seen very clearly, that is, the substance that allows only some part of the light to pass through them are called translucent.
Oiled paper, eroded glass, butter paper, sunglasses, and plastic are examples of subliminal.

We can divide the substances into groups as opaque, transparent, and translucent.
We have always seen this in the shops, in the stores, in the markets, different types of goods are kept separately. So that it is easy for us to recognize the goods and it looks good and easy to see.
By dividing the substances into such groups, it becomes convenient to study their properties and observe any patterns in these properties.