INTRODUCTION
24 Sep 2021

• There is a massive form of objects everywhere.
  
• All objects around us are made from one or more materials.
  
• A thing are often made from different materials.
  
• Many things may be made up of an equivalent material.

Eg: Pencil, Pen, Dustbins, Desk and chair and so on.

Properties of Materials

Materials are often classified as:

• Solid
• Liquid
• Gas

Some examples are:

Solid→ Stone, Sand and steel

Liquid→ Milk, Oil and Water

Gas → Oxygen, Steam and Nitrogen

Classification on Basis of Look or Appear

Materials are often classified on the basis of how they look or appear to be. Some of the materials are:

Classification on the basis of Soft or Hard

Materials that may be easily compressed or scratched are called Soft.

• For example: Paper, clothes, vegetables etc

Materials that can't be scratched and are difficult to compress are termed as Hard.

• For example: Wood, Plastic, Steel etc.
  

Classification on the basis of Soluble or Insoluble

Materials which will be dissolved in water upon stirring are said to be soluble materials.

Materials that can't be dissolved in water despite how much we stir them are said to be

insoluble materials.

Note:

Not just solid materials, even liquids have the property of being soluble or insoluble.

For Example: lemon juice can easily dissolve in water while oil doesn't dissolve and deposits as a thin layer on the uppermost layer of water.

Objects may float or sink in water

There are some insoluble objects or materials which sink to rock bottom of the surface when dissolved in water while some other float on the surface of the water.

For Example:

Objects may float or sink in water

There are some insoluble objects or materials which sink to rock bottom of the surface when dissolved in water while some other float on the surface of the water.

For Example:

Transparent or Opaque

Objects or materials which may be seen through are said to be transparent objects.

• For Example: Some Plastics, Glass

Objects and materials through which things are often seen but only partially are called

translucent objects.

• For Example: Frosted Glass and Butter paper

Objects which can't be seen through are referred to as opaque objects.

• For Example: Wood, Metals, and Cardboard

Metals and Non-Metals

What is meaning of Classification

The process of sorting and grouping things consistent with some basis.

What are the uses of materials?

What are the explanations we want to group objects?

We need to group objects for variety of reasons:

NCERT SOLUTIONS

1. Name five objects which can be made from wood.

Solution:

Table

Chair

Doors

Desk

Box

2. Select those objects from the following which shine: Glass bowl, plastic toy, steel spoon, cotton shirt

Solution:

The objects that shine are:

Glass bowl,

Steel Spoon

3. Match the objects given below with the materials from which they could be made. Remember, an object could be made from more than one material and a given material could be used for making many objects.

Solution:

Objects	Material
Book	Paper, Wood
Tumbler	Glass, wood, plastic
Chair	wood, plastic
Toy	Glass, Wood, Paper, Plastics, Leather
Shoes	Leather, Plastic

4. State whether the statements given below are True or False.

(i) Stone is transparent, while glass is opaque.

(ii) A notebook has lustre while eraser does not.

(iii) Chalk dissolves in water.

(iv) A piece of wood floats on water.

(v) Sugar does not dissolve in water.

(vi) Oil mixes with water.

(vii) Sand settles down in water.

(viii) Vinegar dissolves in water.

Solution:

i) False                   ii) False                  iii) False       iv) True        v) False          vi) False       vii) True

viii) True

5. Given below are the names of some objects and materials:

Water, basket-ball, orange, sugar, globe, apple and earthen pitcher. Group them as:

(a) Round shaped and other shapes (b) Eatables and non-eatables

Solution:

(a) Round shaped – Basketball, Orange, Globe, Apple, Earthen pitcher

Other shapes – Water, Sugar

(b) Eatables – Water, Orange, Sugar, Apple

Non eatables – Basketball, Globe, Earthen pitcher

6. List all items known to you that float on water. Check and see if they will float on an oil or kerosene.

Solution:

Few items that float on water are as follows:

Sponge’s piece, Plastic bottle, Paper’s piece, Thermocol’s piece, Wood, Plastic ball, Cork

However, these items will not float on an oil or kerosene

7. Find the odd one out from the following:

a) Chair, Bed, Table, Baby, Cupboard

b) Rose, Jasmine, Boat, Marigold, Lotus

c) Aluminum, Iron, Copper, Silver, Sand

d) Sugar, Salt, Sand, Copper sulphate

Solution:

a) Baby – others are made up of wood

b) Boat – others are flowers

c) Sand – others are metals

d) Sand – others are soluble in water