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Classifications: 1 Mark each
$\begin{array}{ccc}\text{S.No}& \text{Changes}& \text{Type of Change}\\ 1& \text{Melting of Ice}& \text{Physical}\\ 2& \text{Dissolving sugar in water}& \text{Physical}\\ 3& \text{Burning rubber}& \text{Chemical}\\ 4& \text{Burning camphor}& \text{Chemical}\\ 5& \text{Melting of wax}& \text{Physical}\end{array}$

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Definition of physical change: 1 Mark
Definition of chemical change: 1 Mark
Examples : 1 Mark
Physical changesare the changes that change the physical traits of the substancewithout making any change in their internal structure.
Example : Melting of ice cubes.
On the other hand, achemical changeis one that affects the internal structure of the substanceso as to form a new substance.
Examlpes : Burning of wood.

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Preparation of curd: 1 Mark
Statement: 1 Mark
Kind of change: 1 Mark
Milk is taken in a vessel and a small quantity of curd is added into it. It is stirred and kept aside for few hours without any disturbance. Finally, the milk is converted into curd.
However, curd formed cannot be converted into milk again.
This indicates that it is an irreversible change.

Answer: Option B. -> False
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B
Not all changesaround us are desired. There are many changes which can harm us. For example, global warming changes the temperature of our planet. However, if the temperature of the earth increases beyond a certain limit, it will become inhabitable for mankind.

Answer: Option B. -> False
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B
When a melted chocolate is kept in a refrigerator it solidifies on cooling. However when it will be kept at room temperature, it will absorb heat and melt again. Hence, it is a reversible process..

Answer: Option B. -> False
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B
On heating a metal expands. However on cooling it contracts. Hence, the given statement is false.

Answer: Option A. -> Both statements are correct
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A
When a metal is heated, it expands and when it is cooled, it contracts. So, heating and cooling both brings about a change.Hence, both the statements are correct.

Answer: Option A. -> irreversible
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A
Changes which can't be reversed are called irreversible changes.
When we cook an omelette, the raw egg gets converted into a semi-solid substance which has different chemical properties. We cannot get the raw egg back from the omelette. Hence, it is an irreversible change.

Answer: Option B. -> False
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B
Making stars by cutting it out from a paper isn't a reversible change because once you cut out a star you can't join it back to make the same paper. Since we started making the stars out of a plane big sheet of paper and ended up with the stars, we cannot join the star back to get the complete sheet of paper back.

Answer: Option B. -> True
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B
A paper boat can be made from a paper and then by unfolding it, it can be converted back to the same paper. Thus, this is a reversible change. Melting of ice, folding of paper, water turning into vapour, inflation of balloon are some of the examples of a reversible change.