Available Answers

1. 1.

   In the following table, tick mark on the changes those are reversible:

   Changes	Reversible	Irreversible
   Steam into water
   Milk into curd
   Growth of a plant
   Dough changing into chapati

    

2. 2.

   Fill in the blanks.

   1. Melting of ice is a ___________ change.
   2. The change in weather occurs due to ___________.
   3. In ___________ changes, the new object can get back to its original form.
   4. In ___________ changes, the altered forms of substances cannot regain their original forms.
   5. Changing of milk into curd is an ___________ change.
   6. When we cool steam, it ___________ to form water.
   7. In ___________ changes, new substances are formed.
   8. In ___________ changes, no new substances are formed.
   9. A child grows into an adult, it is a ___________ change.
   10. Bursting of a balloon is a ___________ change.
3. 3.

   Tick (√) the correct answer:

   1. Melting of ice is
      1. an irreversible change
      2. a physical change
      3. a chemical change
      4. none of these
   2. A new substance is formed in
      1. a slow change
      2. a physical change
      3. a chemical change
      4. a fast change
   3. Chemical changes are
      1. always reversible
      2. always irreversible
      3. mostly reversible
      4. mostly irreversible
   4. A change in a substance can be brought about by
      1. heating
      2. burning
      3. freezing
      4. all of these
   5. Growth in living being is
      1. a physical change
      2. a chemical change
      3. a slow change
      4. a fast change
4. 4.

   Fill in the blanks:

   1. _______________ change can easily be carried out in reverse direction.
   2. _______________ change cannot be easily carried out in reverse direction.
   3. Combustion is a _______________ change.
   4. When some solids are heated, they change directly into vapour. This process is called _______________.
   5. On heating some substances expand in size. This is known as _______________.
5. 5.

   Write 'T' for true and 'F' for false:

   1. Cooking of food is a chemical change.
   2. Liquids contract on heating.
   3. Tearing of paper is irreversible.
   4. The evaporation of liquid is an irreversible change.
   5. Sugar is soluble in water.
   6. Physical changes can be reversed.
   7. Most chemical changes cannot be easily reversed.
6. 6.

   Match the following:

   Column I	Column II
   1. Changes	a. Objects revert to original form
   2. Change in weather	b. Temporary changes
   3. Day and night	c. Permanent changes
   4. Reversible changes	d. Rotation of Earth
   5. Physical changes	e. Revolution of Earth
   6. Chemical changes	f. Continuous process