Question

E Answer the following questions,
1. Give two examples of changes in which energy
is evolved.
2. What type of change is involved in heating sugar?
3. State five physical changes observed by you.
4. Write important differences between physical and chemical changes.
5. Give two examples of physical changes and two examples of chemical changes.
6. Changes involve energy. Explain it,
7. Burning of a candle is considered as a physical as well as chemical change. Explain.
8. What happens when water is added to quick lime? What kind of change is it?​

Answer 1

Answer:

1. When sodium carbonate is mixed with water heat is evolved.

when we light a stove heat is evolved.

2. when we heat sugar it's start to being black in color.

3. Melting if ice

Drying of clothes

Boiling of water

Formation of water vapour

Melting of ice cubes

Formation of instrument form their sourses.

4. The physical changes are temporary while the chemical changes are permanent.

5. physical changes:

Stool from wood

Nails from steel

Chemical changes:

Burning of wood

Corrosion of steel

6. The changes in which energy evolved are the exothermic chemical reaction

Example: Reaction of H2O with NA2CO3.

7. The burning of candles is physical change because the we can convert that wax with new candle.

The burning of candles is chemical change because the rope in it burns completely and can't be came in use.

8. When water is added to quick lime, slaked lime as a precipitate is formed and heat is evolved. It is chemical change because it is permanently change it's state.

Explanation:

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