NCERT SCIENCE CLASS 6--sorting materials into groups -chapter 4- study material

SORTING MATERIALS INTO GROUPS- CHAPTER 4 -IMPORTANT TOPICS

NCERT SCIENCE CLASS 6--sorting materials into groups -chapter 4- study material

Look at this picture. How nicely the hats are arranged on each shelf! Have you ever wondered why we are sorting and arranging things? What is the need for sorting different materials and which are the criteria for sorting? Is sorting materials into groups makes our task easier?

In this session, we can discuss the sorting of materials into groups based on their properties. The objects we see around us are made up of one or more materials like metal, plastics, glass, wood, mud, etc. You can make a list of materials that are around you and group them according to the material by which it is made up of.

Certain objects that we choose may be using different materials. For example, you may have chairs made up of wood, plastic, or metals at home.

plastic chair

wooden chair

Similarly, we can find that a plate, pen, or cot made of different materials. Make a list of objects and the materials by which each one can be made.

Contrary to this, we can think about a material like wood or plastic and list out objects made by this. For example, using cotton, we can make clothes, bed sheets, bags, curtains, etc. Make a table of items like this and find out five items each.

So we can find that objects around us are made of different materials and one material could be used for making many different objects.

PROPERTIES OF MATERIALS

When we are choosing a material for making an object, we need to consider many things like its availability, properties, cost factor, manufacturing methods, etc. Among this, the most important factor is the properties of the material. If we know the properties, sorting of materials into groups is easy. Some of the properties that are discussed here are appearance, hardness, solubility, floating, and transparency.

(a) Appearance

copper

Materials are always different in their appearance and we can make out it from its texture and luster. Metal looks different from wood. Metals like gold, silver iron, copper, etc are lustrous. On exposure to air for a long period of time, iron and copper may become dull. But when it is freshly cut, it shines.

(b) Hardness

Certain objects around you can be compressed easily whereas other objects are difficult to compress. A sponge is easily compressible. You can make a mark on wood with an iron nail by scratching on it. That means iron nail is more hard than wood.

Materials that can be compressed or scratched easily are called soft material and materials which are not easy to compress are called hard materials.

soft sponge

hard rock

    (c) Solubility

You might have noticed that some of the objects dissolve completely in water and some of them do not dissolve. This is one of the important properties for sorting materials into groups. On dissolving salt or sugar in water, it gets soluble easily. If you are adding and mixing chalk powder in water, it may not be dissolving completely.

The substances that are completely dissolving are called soluble substances. Substances that do not mix with water and do not dissolve even after stirring are called insoluble substances.

Solubility is applicable to liquids and gases also. On mixing water and vinegar, it is easily miscible. But on mixing oil and water, we will get two separate layers. Some gases like oxygen are soluble in water. We know that aquatic living things are depending on dissolved oxygen in the water.

fish need oxygen

   (d) Floatation

ice floating

We have seen ice floating on water. Depending on the density, objects can float or sink. The object which is less dense will float. Ice is less dense than water. Similarly, a dry leaf thrown into a pond floats in water, while a stone sinks. When a few drops of honey are poured into a glass of water, it sinks.

 (e) Transparency

transparent glass

Can you see through these glass tumblers? Yes, they are transparent. Substances or materials through which things can be seen are called transparent materials. In our daily life, we come across many transparent materials.

frosted glass

When we are looking through frosted glass, we can not the other side clearly. It allows the light to pass through it partially. Such materials through which objects can be seen partially, not clearly are called translucent. You can think about more examples of this.

wooden plank

Are you able to see the other side when you look through these wooden logs? The materials like wood and metals will not allow the light to pass through it. Hence we can not see the other side. These materials are called opaque materials. List out more examples of opaque objects.

 So we can sort different materials into different groups based on the similarity of their properties. Grouping or sorting is done for our convenience. In shops, libraries, textile,s and even at home, we store different things by sorting things for our easy access. Grouping or sorting of materials into groups is helpful to study the properties of groups and to observe the pattern in these properties.