Question

Which of the following is a physical but irreversible change?

• A. Burning of matchstick
• B. Melting of ice cream
• C. Breaking of a flower vase
• D. Lighting up of an electric bulb

Answer 1

The correct option is C

Breaking of a flower vase

Explanation for the correct answer:

C) Breaking of a flower vase

1. Physical changes are changes affecting the form of a chemical substance, but not it's chemical composition.
2. A reversible change is a chemical change where no new materials are created and the original material can be recovered
3. A change is called irreversible if it cannot be changed back again. In an irreversible change, new materials are always formed.
4. Breaking of a flower vase into pieces is a physical change. Because there were no new compounds formed and only the change is in shape and size of the material.
5. This cannot be reversed back into the beautiful flower vase. We cannot stick back all the broken pieces. So that it is a irreversible

Explanation for the incorrect answer:

A)Burning of matchstick

1. The formation of new substances and the formation and breaking of strong chemical bonds characterize chemical change.
2. When we light a match, we emit both carbon dioxide and water, and a residue of inorganic salts(ash) remains.

B)Melting of ice cream

1. Melting ice is a physical change because it involves a change in the physical state of water, from ice to liquid water.
2. Furthermore, no new chemical substances are formed during the transformation, and the transformation is reversible.
3. Simply freezing water will return it to its original state as ice.

D)Lighting up of an electric bulb

1. This is a physical change because in this process, electric energy is being converted into heat & light energy only.
2. There is no change in chemical composition in this process.
3. And also it is a reversible change because when we switch on a light bulb it glows and it is not like it will not glow again.

Hence the answer is option C