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Which of the following is a reversible change?

A reversible change is a change that can be brought back into its original form. “A substance can return to its original state is classified as reversible change.” No new substance is formed in a reversible reaction. Most of the physical changes are reversible.

An irreversible change is a change that cannot be brought back into its original form. Once it changed, it is permanent in nature. All chemical changes are irreversible changes.

The main difference between reversible and irreversible is that the reversible reaction is only a temporary change while irreversible is mostly permanent in nature.

Q.1 Which of the following is a reversible change?

(a). Burning of the candle

(b). Cutting wood in pieces

(c). Blooming of flowers

(d). Melting of ice

Answer = Option (d)

The melting of ice is a reversible change whereas the burning of candles, cutting of wood into pieces, and blooming of flowers are examples of irreversible change.

Explanation:-

(a). Why is the burning of a candle an irreversible change?

Once the candle is burned, we can’t bring back its burnt candle thread, hence, the change that occurs in the burning of a candle is an irreversible type of change.

(b). Why is the cutting wood in pieces an irreversible change?

Like when we cut the innocent tree wood into pieces then we can’t rejoin the cutting piece into the original wood, hence, cutting wood in pieces is an irreversible process.

(c). Why is the blooming of flowers an irreversible change?

Of course, once the bud blooms and changes into a flower, we can’t make the flower change into a bud again. Hence, it is irreversible.

(d). Why the melting of ice is a reversible change?

Once the ice is melted, it turns from solidified ice to a liquid water state, we can again turn the water into the ice by decreasing the temperature. Hence, the change that occurs in the melting of ice is a reversible change.

Q.2 Which of the following is a reversible change?

(a). Burning of wood

(b). Curdling of milk

(c). Ripening of fruits

(d). Freezing

Answer = Option (d)

The freezing process is a reversible change while the burning of wood, curdling of milk, and ripening of fruit are examples of irreversible change.

Explanation:-

(a). Why is the burning of wood an irreversible change?

When the wood is burned, it changes into a new substance like ash, heat, CO2 gas, etc. that cannot be reverted back, hence, the burning of wood is an irreversible change.

(b). Why the curdling of milk is not a reversible change?

When the milk is changed into curd then the change is permanent in nature as milk loses its chemical properties and distorted the internal structure. Hence, the curdling of milk is an irreversible change.

(c). Why is the ripening of fruit an irreversible change?

“Ripening is associated with a change in composition”. When the ripening of fruit is done then the changes that occur in pigment present in the skin of the fruit are not reversible.

(d). Why is the freezing a reversible change?

Freezing is the process of converting liquid into solid by decreasing the temperature below the freezing point. But we can change the freezing substance into a liquid state by increasing the temperature.

Hence, the freezing process is a reversible process.

Q.3 Which of the following is an example of reversible change?

(a). Evaporation of water

(b). Melting of wax

(c). Germination of seed

(d). Rusting of iron

Answer = Option (a), (b)

The evaporation of water and melting of wax is an example of reversible change while the germination of seed and rusting of iron is an examples of irreversible change.

Explanation:-

(a). Why is the evaporation of the water a reversible change?

When the water in the liquid state is evaporated, it turns into water vapor (gaseous state) then water vapor can also be converted into a liquid state with the help of the condensation process. Hence, the evaporation of water is a reversible process.

(b). Why is the melting of wax a reversible change?

In the melting of wax, only the physical state of the wax changes from solid to liquid. Molten wax can be again converted to solid wax.

(c). Why is the germination of a seed an irreversible change?

The germination of the seed is a chemical process in which many enzymes and hormones work to germinate a seedling from a seed. Once the seedling grows into the plant, it cannot be reversed. Hence, the germination of the seed is an irreversible change.

(d). Why is the rusting of iron an irreversible change?

During rusting of iron, the Fe undergoes an oxidation process and changed into a new substance which is called iron oxide(Fe2O3), this process cannot be reversed, hence, the rusting of iron is an irreversible change.

FAQ

Give some examples of reversible changes?

  • Freezing of water
  • Melting of ice
  • Evaporation of water
  • Melting of wax
  • Adding sweetener to coffee or tea
  • Boiling of water
  • Mixing sand and water
  • Dissolving sugar in water

Is the burning of coal an example of reversible change?

“Coal is made up of carbon and hydrocarbons, which contain energy that can be released through combustion”. When the coal is burned, the carbon is converted into CO2 and hydrogen into water. Hence, new substances are formed that cannot be reversed, therefore, the burning of coal is not a reversible reaction.

Which of these is a reversible change “Boiling an egg” or “Boiling of water”?

Boiling an egg is an irreversible change whereas boiling water is a reversible change.

When the egg is boiled at an elevated temperature then a distortion happens in the internal structure of the egg that causes a change in its molecular structure. Hence, the original egg cannot be brought back, once it is boiled or fried.

When the water is boiled it turns into water vapor. The water vapor can be converted into a liquid state by the action of the condensation process. Hence, the boiling of water is a reversible change.

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