Kids Learning Science

 

4th Standard Science Term-I

Matter and Materials

  I. Materials  

Everything in the universe is a matter.  We need to explore many different materials to make sense of our world.

The matter from which a thing is made of is called material.  

For example : Chair is made of wood, Eraser is made of rubber, Candle is made of wax.

  II. Properties of Materials  

We can measure, see or feel the materials.  Different types of materials have different properties that make them useful for various purposes.  Most materials have more than one property.  They can be hard or soft, shiny or dull, smooth or tough and flexible or rigid.

  1. Hard and Soft Materials  

Materials which cannot be easily compressed, cut, bent or scratched are called hard materials.  

Example : Brick, bone and steel.

Materials which can be easily compressed, cut, bent or scratched are called soft materials.

Example : Foam, clay and skin.

  2. Shiny and Dull Materials  

Materials which reflect the light well are called shiny materials.  

Example : Stainless steel, gold and diamond.

Materials which do not reflect the light well are called dull materials.

Example : Candle, Paper and jute bag.

  Try to Answer  

Collect some objects from your house and classify them as shiny or dull materials.

  3. Rough and Smooth Materials  

Materials which have ups and downs on their surface are called rough materials.  

Example : Brick, rock and tyre.

Materials which do not have ups and downs on their surface are called smooth materials.  

Example : Mirror, silk cloth and tiles.

  4. Flexible and Rigid Materials  

Materials which can be bent or stretched easily are known as flexible materials. 

Example : Rubber band, electric wire and cycle tube.

Materials which cannot be or stretched easily are known as rigid materials.  

Example : A stick, wooden scale and stone.

  5. Waterproof Materials  

Materials that do not allow water to pass through them are called waterproof materials.

Example : Raincoat and aluminium foil of tablet strip.

  Think and Answer  

  Do you have a raincoat? What is its use?  

  Activity  

Take a glass bowl.  Fill three fourth of it with water.  Put an orange fruit with peel and a orange fruit without peel.  Observe which orange floats? Why?

  III. Transparent, Translucent and Opaque objects  

  Have you ever seen through the bus window?  

Some objects allow light to pass through them.  This helps us to see through them as the window of a bus.  Let us see how different objects behave with light.

  1. Transparent Objects  

Transparent objects allow the light to pass through them.  So, we can see other objects clearly through transparent objects.  Example : Air, glass and pure water.

  2. Transparent Objects  

Some light passes through

                                       Vegetable oil

Translucent objects allow some light to pass through them.  So, we cannot see objects clearly, but we see them as blurred images through them.

Examples : Paper soaked in oil, snow and vegetable oil.

  3. Opaque objects  

Opaque objects do not alIow light to pass through them.  So, we cannot see through these objects.

Examples : Wood, Stone and metals.

  Think and Answer  

  Why should we build the walls of the house with bricks (opaque material) instead of glass (transparent material)?  

  IV. Reflection of Light  

We see the world around us with the help of light.  Where do we get the light from? Light may come either from the Sun or from other sources like an electric lamp or a bulb.   The objects that give off light are called light sources.

When light falls on a transparent material it passes through it.  However when light falls on a polished surface of an opaque material, it does not pass through it.  It bounces back.  The bouncing of light by any smooth or polished surface is called reflection.

When you look into the mirror, you can see your own face on the mirror.  What you see is a reflection of your face in the mirror.  We also see reflections of other objects that are in front of the mirror.  These reflections are formed by light and they are called images.

  Try to Answer  

Try to see your face on some materials like mirror, exam pad, new stainless steel plate, table top and water in a plate.  What are the materials that show your face clearly? Do you know why?

  Activity  

Reflection of Light

Material Required/Needed

A plane mirror and a torch light.

How to do?

1. Make your room dark by closing the door and windows.

2. Ask your friend to hold a mirror in his/her hand at one corner of the room.

3. Stand at another corner with a torch in your hand.

4. Switch it on.

5. Direct the light from the torch onto the mirror.

6. Answer the following from your observation.

a) When you change the angle of the mirror, what happens to the light?

b) Are you able to direct the reflected light using the mirror?

  More to Know  

Mirrors can reflect sound waves too.  So they were used in the Second World War to detect sounds coming from enemy aircraft.