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1. 1.

   Write T for the true statement(s) and F for the false one. Correct the false statement(s).

   1. A new substance is formed in a reversible change.
   2. Breaking of glass is a reversible change.
   3. Crushing chalk is an irreversible change.
   4. Blooming of flowers is an irreversible change.
   S A M P L E

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   Answer:

   S A M P L E

   1. False A new substance is not formed in a reversible change.
   2. F
   3. ...
   4. ...
2. 2.

   Identify the following changes as reversible/irreversible.

   1. Changing of water into vapour.
   2. Melting of chocolate.
   3. Growth of a puppy into a dog.
   4. Burning of a firecracker.
   5. Woolen yarn into a knitted sweater.
   S A M P L E

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   Answer:

   S A M P L E

   1. Reversible
   2. Reversible
   3. Irreversible
   4. Irreversible
   5. Reversible
3. 3.

   Choose the correct option.

   1. Which of these is a reversible change?
      1. Dough to chapatis
      2. Burning of candle.
      3. Rice grains to cooked rice
      4. Melting of kulfi
   2. Which of these is an irreversible change?
      1. Melting of wax
      2. Freezing of water
      3. Boiling of water
      4. Burning of paper
   3. Baking a cake is an example of
      1. physical change
      2. irreversible change
      3. chemical change
      4. both (b) and (c)
   4. The order of expansion in solid, liquid, and gas
      1. solid > liquid > gas
      2. solid < liquid < gas
      3. solid > gas > liquid
      4. solid < gas < liquid
   5. Expansion gaps are kept in railway tracks because of
      1. expansion of rails in hot weather
      2. contraction of rails in hot weather
      3. expansion of rails in cold weather
      4. contraction of rails in cold weather
   S A M P L E

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   Answer:

   S A M P L E

   1. (d) Melting of kulfi
   2. (d) Burning of paper
   3. (d) both (b) and (c)
   5. (a) expansion...
4. 4.

   Fill in the blanks with the correct words.

   1. Melting of ice-cream is an example of a/an ____________ (reversible/irreversible) change.
   2. Ripening of fruits is an example of a/an ____________ (reversible/irreversible) change.
   3. Cooking of food is an example of a/an ____________ (reversible/irreversible) change.
   4. Breaking of glass is a ____________ (physical/chemical) change.
   5. ____________ (Heating/Cooling) causes steam to change into water.
5. 5.

   Write one word for the following.

   1. A change that can be reversed.
   2. A  change that cannot be reversed.
   3. A change where no new substance is formed.
   4. A change where a new substance is formed.
6. 6.

   Identify the changes that occur when the following happen.

   1. Freezing of water
   2. Making curd from milk
   3. Boiling on egg
   4. Melting of butter
   5. Tearing of paper