Changes around us Worksheet-8

Changes around us Worksheet-8

 

Multiple-Choice Question:

  1. Which of the following statement is TRUE?

(A) A physical change is always an irreversible change

(B) A chemical change is always a reversible change

(C) Both of these

(D) None of these

 

  1. When chlorine is added to water in the swimming pool, it dissolves.______ change will take place.

(A) Physical         (B) Chemical        (C) No

 

  1. When jelly cubes are heated, they melt.

(A) It’s a reversible change             (B) It’s an irreversible change

(C) None of these

 

  1. When wood is left in water, it rots.

(A) It’s an irreversible change        (B) It’s a reversible change

(C) None of these

 

  1. Roasting of chicken is:

(A) None of these                            (B) A chemical change

(C) A physical change

 

  1. When petrol is burned, it powers a car.

(A) It is a physical and irreversible change

(B) It is a chemical and reversible change

(C) It is a physical and reversible change

(D) It is a chemical and irreversible change

 

  1. An ironed shirt to wrinkled shirt is a/an:

(A) Irreversible change          (B) None of these

(C) Reversible change

 

Comprehension:

Take 100 ml of water and some amount of salt. Gradually add the salt to the liquid until it has completely dissolved and a saturated solution is formed. Take four saucers and put about 30 ml of this saturated solution in each one. Place one saucer (a) on a sunny window sill, (b) one near the heated and (c) one on a shelf away from the sunlight. Cover the fourth saucer with a plate and place it anywhere in the room. Answer the following questions on the basis of observation after one week.

  1.  In which saucer water has evaporated completely?
  2. In which saucer most of the liquid is remaining?
  3. In the saucers where the liquid is evaporated completely, what is left behind?
  4. Is the salt left behind different from the salt you mixed into water?

 

Answer Key:

  1. (D)
  2. (B)
  3. (B)
  4. (B)
  5. (B)
  6. (D)
  7. (C)
  8. The liquid in the saucer kept on a sunny window sill  evaporated completely and the salt remained stuck to the saucer.
  9. The solution in the saucer furthest from the heat evaporated least.
  10. Salt is left behind.
  11. No, it is not different from the salt we mixed with water.