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प्रश्न
Change is the law of nature which occurs in everyday life.
State when a substance [i.e. matter] undergoes a kind of change.
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उत्तर
Change is the law of nature that occurs in everyday life. A substance [i.e. matter] undergoes a kind of change when subjected to energy changes.
The matter is said to undergo certain changes when energy is added to the matter or removed from the matter.
Examples of Changes are:
- Ice melts on supplying heat to it.
- Milk changes into curd when a little curd is added to hot milk.
APPEARS IN
संबंधित प्रश्न
Fill in the blank.
Heat is .................... by a gas during the process of condensation.
State whether the following is physical or chemical changes.
(energy produced) dissolving sugar in water —
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.
Classify the following as physical or chemical change :
Condensation of steam
Differentiate between a physical change and a chemical change with reference to – Energy change taking place during the respective change.
Explain the term – ‘sublimation’. Is sublimation of naphthalene – a physical or a chemical change. Give reasons.
State why addition of sodium chloride to water is considered a physical change, while addition of dilute sulphuric acid to zinc is considered a chemical change.
Give the reason why the following is considered as chemical changes.
A piece of magnesium strip is dropped into a beaker containing dilute hydrochloric acid.
Digestion of food is a physical change.
Cutting a log of wood into pieces is a chemical change.
