Changes and its classification - class-VII

When a nail is added to acidic copper sulphate solution, the colour changes from blue to green.
Copper sulphate reacts with iron to form iron sulphate.

The statement (A) is true.
Melting of ice is reversible change.
Burning of magnesium is irreversible change.
Rusting of iron is irreversible change.

A physical change may be reversible. For example, melting of ice is a reversible change.
Also, a chemical change may be reversible. For example, the reaction between $\displaystyle N _2$ and $\displaystyle H _2$ to form $\displaystyle NH _3$ is a reversible chemical change.

Physical changes are generally reversible (e.g., melting ice), whereas chemical changes are generally irreversible. Therefore, the statement that physical changes are not reversible is incorrect.

Cooking of rice is both irreversible and endothermic reaction. i.e once cooked rice cannot be made rice back and the rice absorbs heat from the external sources and utilizes for its cooking so it is endothermic.

The growth of seedlings in a crop is a desirable change i.e the changes which are beneficial to nature or which does not cause any harm to nature.

A seed growing into a tree is an example of a slow and natural process. Slow because it takes days to sometimes months for a seed to develop into a sapling and then years to a develop into a tree. All these processes occur naturally using all natural resources like water, sunlight, soil.

The planets around the sun, blinking of traffic lights and motion of blades of a fan rotating at uniform speed are all periodic changes.
Changes which are repeated after regular intervals are called periodic changes.

According to transition state theory, two molecules interact with each other when they are aligned in a proper orientation.

It is a periodic change $-$ because changes that occur after a fix interval of time is known as periodic change.

It is true.

When a nail is added to acidic copper sulphate solution, the color of the deposit on the iron nail is brown. Copper sulphate reacts with iron to form iron sulphate and copper. Brown colored copper deposits on nail.

A change in which a substance changes its physical properties like appearance, texture, colour, odour, melting points, boiling points, density, solubility, polarity etc... are called physical changes. 

When a substance cools off, the size of substance, vibrations, a temperature of the substance decreases, as the heat is dissipated out resulting in the decrease in the size of the substance, and the internal vibrations between the molecules also decrease as the temperature decreases, due to the loss of heat.

All metals have a property of expansion when heated. Since the metal ball is heated, it will expand and will not pass the ring now.

Things or processes which cannot be reversed are called irreversible process Burning of coal is irreversible as it will not produce coal again.

Galvanization(Coating
of non-reactive metal on iron) and painting prevents iron to get in contact with moisture thus prevent it from rusting. 

A chemical change is permanent. A new substance is formed.

Vapor is another physical state of water. Water can be obtained from the  condensation of vapor. This is a physical and reversible change.

Magnesium ribbon burns with dazzling light in air and forms magnesium oxide.
$2Mg+O _2\rightarrow 2MgO$.
The above change is a chemical changes as new substance is  formed after change. Original
substances cannot be retrieved by simple physical processes.So it is chemical change.
Hence option A is correct.

A
chemical change is the process in which chemical composition of the
substance is changed,and physical composition may or may not changed burning of coal that is carbon(C) in presence of oxygen gives a different chemical substance $CO _2$. So, it is a chemical change. Hence option A is correct.

In melting of wax, only the physical state of the wax changes from solid to liquid. Solid wax can be obtained from molten wax. Molten wax can be again converted to solid wax. This is an example of physical and reversible change. Hence, option A is correct.