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प्रश्न
Compare the energy changes involved during a physical and a chemical change.
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उत्तर
- Physical change: No gain or loss of energy during physical change.
The energy required for completion of a physical change is released when the change is reversed. - Chemical change: Energy is either absorbed or evolved during the chemical change.
The energy in the form of light, percussion (pressure), or generally heat energy is required for a chemical change.
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संबंधित प्रश्न
When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.
Write true or false for the statement
A natural change can also be a desirable change
Write short answer.
Give two examples of periodic changes
What are reversible and irreversible changes ? Give one example for each.
What do you observe when :
lighted match stick is brought near the mouth of the test tube containing hydrogen gas.
Classify the following as a physical or a chemical change.
Drying of wet clothes
Given reason:
Burning of paper is a chemical change.
What will you take into account while identifying the following?
A physical change in a substance.
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.
Give a reason why
Freezing of water is a reversible change while burning of a candle – an irreversible change.
