Question

give scientific reasons ​

Answer 1

Explanation:

1. Because chemical composition of water i.e H2O remains same.

2. bcoz Ash can't be turned back to paper, so, its irreversable.

3. Curd can't be changed back to milk, as lactic acid is produced.

4. bcoz Co2 is released, its a chem. reactiom

5. bc. only the state is changed, however, the chem prop. remains the same.

6. it causes pollution

7. it rotates at equal intervals in occilatory motion.

8. it takes place rapidly.

hope it helps!!

Answer 2

1. A physical change is reversable. As water can be converted into water vapour by heating it and again water vapour can be converted to water by the process of condensation.So,it's a physical change.

2. By burning a paper turned it into ashes. As ash can't convert into paper. So,it's a irreversible change.

3. Milk turn into curd by a bacteria named lactobacillus. During this conversion the bacteria break down the milk and form it into curd. As the curd can't change into milk . So, it's a chemical change.

4. Fermentation is an anaerobic process in which yeast breakdown sugar molecules into alcohols.

As there is a change in molecular formula. So it's a chemical change.

5. Sublimation is a typical condition in which some material directly change from solid into has without going into liquid form and again by compression at low temperature and high pressure it can convert into its solid form. So it's a physical change.

6. Yes, burning fuel mostly those who are highly inflammable can lead to undesirable change. It's can happen in some certain conditions. Like if the oxygen and surface for burning is high then it may leads to a vigorous flame on the other hand if oxygen is low and surface area is less then it will lead to a normal fire.

7. Rotation of fan is a period change because if we observe a single blade of fan then we can not that a single blade of fan took some time to complete a full circle and repeat the same motion.

8. Normally cooking gas like LPG are highly inflammable. So when it is burned it's molecules get excited which leads to a fast change.

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