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प्रश्न
Define a chemical change. Give two examples of the above changes.
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उत्तर
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.
संबंधित प्रश्न
Classify the following as chemical or physical change:
Burning of paper and wood
Classify the following changes as physical or chemical: curdling of milk
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
Tick (√) the correct alternative from the choice given for the following statement.
A substance which can not sublime is
True or false
Change of seasons is a non-periodic change.
True or false
Dissolving of a solid in liquid is a physical change.
Classify the following as physical or chemical change :
Formation of curd from milk
Which of the following are physical changes and which are chemical changes ?
Freezing of water
Classify the following as a physical or a chemical change.
Melting of wax
Classify the Following as a Physical Or a Chemical change.
Glowing of an Electric Bulb
Read the paragraph and note down the various types of changes it mentions.
It was nearing six o'clock in the evening. The sun was setting. A breeze was blowing. Leaves on the tree were shaking. Sahil was sitting in the courtyard, rolling balls of wet soil, and shaping them into various toys. Then he felt hungry and went into the house. Mother made a dough from wheat flour and fried purees. While eating hot purees, his attention was drawn outside the window. It had started raining. There was lightning, too. Sahil was enjoying his dinner in the dim light.
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.
Periodic and non-periodic change
Ammonium chloride is also a sublimable solid. Give a reason why the sublimation of ammonium chloride involves a physical and a chemical change.
Photosynthesis is a natural process by which green plants manufacture food in the presence of sunlight.
State the conclusions which can be drawn, to represent photosynthesis as a physical or a chemical change.
Fill in the blank with the appropriate word of the statement given below:
Germination of seeds is considered a __________ 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.
Compare the energy changes involved during a physical and a chemical change.
Select the chemical changes from the following list of changes
Respiration in mammals.
Name the following.
The gaseous product of the chemical change which takes place during respiration in living organisms.
What type of change is colouring of a paper?
