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प्रश्न
Give three reasons why melting of wax, is considered a physical change while burning of a candle, a chemical change.
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उत्तर
Melting of wax is a temporary and reversible change on cooling, wax solidifies, and no new product is formed while burning of a candle is a permanent change i.e. products are not convertible, a new substance is formed having different composition & different properties.
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संबंधित प्रश्न
Name a chemical change which takes place in presence of:
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.
What will you take into account while identifying the following?
A chemical change in a substance.
Change is the law of nature and occurs in our everyday life, at all times and in all places.
Differentiate between the following change with a suitable example.
Natural and man-made change.
Change is the law of nature which occurs in everyday life.
State when a substance [i.e. matter] undergoes a kind of change.
State which of the following pertain to – chemical changes.
- Substance retains its identity.
- The change is permanent.
- No new substance is formed.
- Is easily reversible.
- Produces one or more new substances by a change in its composition.
- The change is temporary.
- The composition and properties of the original substance are not altered.
Select the chemical changes from the following list of changes
Vaporisation of water into water vapour.
Distinguish physical and chemical changes.
Classify the following as physical or chemical properties
Metallic sodium is soft enough to be cut with a knife.
Iron pipes coated with zinc do not get rusted easily.
