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प्रश्न
A burning candle shows both physical and chemical changes. Explain ?
Burning of a candle is both a physical and chemical change.
उत्तर १
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.
उत्तर २
When a candle is lighted, some of the solid wax first melts and turns into liquid, then it turns into vapours to produce a flame. New substances CO2 and H2O vapours are formed along with the evolution of light and heat energy. This shows a chemical change. When some of the molten wax drops to the floor, it again solidifies. Which shows a physical change. Thus the melting of candle wax is a physical change and the production of CO2 and H2O represents chemical change.
संबंधित प्रश्न
Tick the most appropriate answer.
3. Physical changes are
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- periodic,
- temporary
- irreversible.
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Changes that occur in nature are called ........................
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lighted match stick is brought near the mouth of the test tube containing hydrogen gas.
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Chemical change occurs as a result of __________ between two substances.
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Heat is ________ by a gas during the process of condensation.
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Classify the following as physical or chemical changes :
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Classify the following as a physical or a chemical change.
Boiling of water
Distinguish between the following.
Physical change and chemical change
Change is the law of nature and occurs in our everyday life, at all times and in all places.
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The term involved in the change of state from – ‘water to ice’ – which is a physical change.
Select the chemical changes from the following list of changes
Glowing of an electric bulb.
Match the examples of changes in List I with the correct type of change in List II.
| List I | List II |
| 1. Burning of paper | A: Physical change |
| 2. The ringing of an electric bell | B: Chemical change |
| 3. Curdling of milk | |
| 4. Electric light is switched on | |
| 5. Melting of butter |
Classify the following changes as physical and chemical changes
A rough piece of wood is sanded and polished resulting in change in texture, Rusting of a iron nail, Painting the grill, Bending a paper clip, Pounding silver into thin plate, Rolling the chappathi dough into thin wire, Occurrence of day and night, eruption of volcano, burning of matchstick, dosa from the batter, blinking of eyelids, occurrence of a thunderstorm, rotation of the earth, formation of eclipses.
| Sr. No. | Physical changes | Chemical changes |
| 1. | ||
| 2. |
Give an example of a physical change in which the color of the substance changes.
