Page 74 - Science Class 06

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i Changes are always going on everywhere in nature.
i Change is the spice of life indeed.
i Change can be classified in view of various factors— speed, utility, time-pattern,
permanency, reversibility and the types of reactions.
i The chemical changes in which heat energy is absorbed are called endothermic changes.

i The new substance produced in a chemical reaction cannot be reversed in order to obtain the
original reactants.
i No change can take place at all, anywhere, in any manner, unless there is an interaction
between two things or among more than two things.

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Exercise
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A. Tick (3) the correct op on.
1. An earthquake is a change that is said to be:
(a) reversible (b) beyond our control
(c) non-periodic (d) desirable
2. Rus ng of iron is a:

(a) slow chemical change (b) fast physical change
(c) reversible change (d) exothermic change
3. Burning of a matchs ck is a:
(a) fast physical change (b) fast chemical change

(c) slow chemical change (d) periodic change
4. Produc on of hydrogen and oxygen from water is a:
(a) physical change (b) chemical change

(c) reversible change (d) none of these
B. Name the correct term for.
1. the change that occurs over a period of me : _____________________________
2. the change that is not worth desiring : _____________________________
3. the change that lasts forever : _____________________________
4. the change that is not reversible : _____________________________
5. the changes that are useful to mankind : _____________________________
6. the changes that can be reversed : _____________________________
7. behaviour of energy in change of vapour into water : _____________________________
8. change that take place unexpectedly : _____________________________
C. Tick (3) the chemical changes.
1. dissolving of salt in water 2. burning of incense
3. evapora on of water 4. bending of a thin wire

5. ripening of a mango 6. mending a pencil

74 Science-6