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CHEMISTRY [3 Mark Question Answer]

Physical and Chemical Changes · ICSE STD 8 (ICSE - English Medium). 5 questions.

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[3 Mark Question Answer]

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5 questions · timed · auto-graded

Question 13 Marks
Given reason: Burning of paper is a chemical change.
Answer
When a piece of paper is burnt a new substance ash is produced. Even when the burning is stopped, the ash cannot be changed back into paper. This shows that the formation of the ash from paper is a permanent and irreversible change.
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Question 23 Marks
A burning candle shows both physical and chemical changes. Explain ? Burning of a candle is both a physical and chemical change. 
Answer
A burning candle produces wax vapours which solidify and form wax again is physical change. At the same time wax on burning produces water vapours and carbondioxide which escape into the atmosphere which are new substances with new properties. It is a chemical change.
Hence burning of candle shows both physical and chemcial changes.
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Question 33 Marks
Given reason: Freezing of water to ice and evaporation of water are physical changes.
Answer
Freezing of water to ice and evaporation of water are physical change because water can be brought back to its original $($liquid$)$ form by
$1.$ We can heat the ice to bring it back to water.
$2.$ We can cool down the vapours to bring it back to water.
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Question 43 Marks
Define a chemical change. Give two examples of the above changes.
Answer
A permanent change in which new substances are formed whose composition and properties are completely different from those of the original
substances.
Chemical change:
$(i)$ Burning of wood.
$(ii)$ Breathing.
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Question 53 Marks
Define physical change. Give two examples for the above changes.
Answer
Physical chagne : A temporary change in which no new substance is formed, the composition of substance remains the same, though its state, shape and size may change.
Example of Physical change:
$(i)$ Change of water into its vapours.
$(ii)$ Heating of iron rod.
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[3 Mark Question Answer] - CHEMISTRY STD 8 Questions - Vidyadip