SORTING MTERIALS INTO GROUPS (POST-3) (HOTS included)

GOOD MORNING BOYS !
In the last class you learnt about some common characteristics of materials. 
Answer the following questions orally to check how much can you  recall.
1.What are the three states matter exists in?
2. What is the characteristic shine that metals  possess called?
3. Give an example of immiscible liquids.
4. Are chalk and sand soluble substances?

LEARNING OUTCOMES OF THIS CLASS-
By the end of this class you will be able to-
- understand  why do  some objects float and some sink in water.
-distinguish between transparent ,translucent and opaque materials.
-distunguish between good, poor and non- conductors of heat.

MATERIALS MAY FLOAT OR SINK IN WATER
Materials that are lighter than water float on water. Materials that are heavier than water sink into it.

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TRANSPARENCY
You must have seen sunlight coming into your room through the glass window- pane. You can also see things outside your room through your glass window.  Can you see things outside your room through the wall ? Definately not ! This is because light cannot pass through the wall.
 Materials can be classified into three types, depending on whether they allow light to pass through them or not.



NOW TRY THIS !
Given below are different objects.  Classify them into opaque , transparent, transculent objects-

WOODEN DOOR   OILY PAPER   CLEAR WATER    BOOK

AIR    METAL    GROUND GLASS     GLASS      BAG


HOTS !

Will transparent or opaque objects form shadows? ( Hint: For a shadow to be formed the path of light has to be blocked. )

CONDUCTION OF HEAT
 You must have noticed that  utensils used for cooking are made of metals but their handles are usually made of wood or plastic. Have you ever wondered why ?
This is because metals conduct heat and plastic and wood do not conduct heat. 
GOOD CONDUCTORS OF HEAT ( CONDUCTORS ) - These are materials like aluminium, cpopper, stainless steel ,iron etc which conduct heat quickly.
NON-CONDUCTORS OF HEAT ( INSULATORS)- These are materials like wood, plastic,air , bakelite which do not conduct heat.


POOR CONDUCTORS OF HEAT - These materials like water and glass that conduct heat very slowly.

HOTS!
Why does you mother sometimes use a cotton cloth to pick up a hot utensil?

DO THE QUESTIONS GIVEN BELOW IN YOUR NOTE BOOK

6. Give reasons for the following statements.
a) A piece of plastic floats in a bucket of water but a 10 rupee coin sinks into water.  -  because the piece of plastic is lighter than water but the 10 rupee coin is heavier than water.

b) Cooking utensils are made of metals but their handles are made of plastic  -  because metals are good conductors of heat and will pass the heat to the food that is in the utensil and has to be cooked. The handles are made of plastic as  plastic is an insulator and we will be able to hold /lift  the  hot utensil by not burning our hand.

c) A ball of cotton is very light, but when it is put into a mug of water ,it sinks into the water -  because the air spaces in the cotton ball get filled with water ,thus making it heavy, and it sinks into water.

7. Distinguish between the following-
a)  TRANSPARENT    TRANSLUCENT      OPAQUE
       MATERIALS           MATERIALS               MATERIALS
  -light can pass          -light can pass         - light cannot pass
   through them           through them            through them at all.
   totally.                      partially.
 eg.glass                      eg. oiled paper       eg. wood

b)  CONDUCTORS OF                NON-CONDUCTORS OF
      HEAT                                        HEAT (INSULATORS)
  -allow heat to pass through       -do not allow heat to pass 
   them.                                            through them.
   eg. metals                                     eg. plastic,wood

This is all for todays class ! Have a good day !