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Question
Give two examples for each of the following cases:
Physical changes which are not reversible.
Solution
(i) Cutting of paper
(ii) Breaking of glass
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Tick the most appropriate answer.
3. Physical changes are
- permanent.
- periodic,
- temporary
- irreversible.
Solve this crossword by using the clues that follow.
Across
1. Energy in the form of sunlight is absorbed by the green plants in this process.
4. The reddish-brown substance formed over iron in the presence of oxygen and moisture.
5. This change is permanent and irreversible.
6. The process in which a solid directly changes into gaseous state.
Down
1. It is the change that takes place in case of swinging pendulum of a clock.
2. Occurrence of this is a non-periodic change as well as a natural change.
3. It is a physical change
State whether the following is physical or chemical changes.
mixing oil with water —
Fill in the blank
Heat is ________ by a gas during the process of condensation.
Which of the following are physical changes and which are chemical changes?
Burning of candle wax, Melting of candle wax, Mixing of iron filings and sand, Burning of wood, Breaking a piece of chalk, Burning a piece of paper, Cutting a piece of paper.
Fill in the blank.
A change, which alters the composition of a substances, is known as a___________ change.
Distinguish between the following.
Physical change and chemical change
Give the reason why the following is considered as chemical changes.
An iron nail kept open in the atmosphere rusts.
What type of change is colouring of a paper?
Paheli’s mother made a concentrated sugar syrup by dissolving sugar in hot water. On cooling, crystals of sugar got separated. This indicates a
