The correct answer is B: boiling of water. Boiling of water is a physical change, not a chemical change. Here's a detailed explanation:
Chemical Change:
A chemical change is a process that results in the formation of new substances with different properties from the original substances. It involves the rearrangement of atoms and the breaking or forming of chemical bonds.
Physical Change:
A physical change is a process that alters the state or form of a substance without changing its chemical composition. It does not involve the formation of new substances.
Now let's analyze each option:
A: Boiling of an egg:
- Boiling an egg involves the denaturation of proteins present in the egg white.
- The heat causes the proteins to unfold and coagulate, resulting in a solid state.
- This is a chemical change because the proteins undergo structural changes.
B: Boiling of water:
- Boiling water involves the conversion of liquid water into water vapor (gas) due to the application of heat.
- The chemical composition of water remains the same, and no new substances are formed.
- This is a physical change as only the state of water changes.
C: Burning of cloth:
- Burning cloth involves a combustion reaction where the cloth reacts with oxygen in the air to produce carbon dioxide, water vapor, and other combustion byproducts.
- The cloth undergoes a chemical change and is converted into different substances.
- This is a chemical change.
D: Burning of paper:
- Burning paper also involves a combustion reaction where the paper reacts with oxygen to produce carbon dioxide, water vapor, and other combustion byproducts.
- The paper undergoes a chemical change and is converted into different substances.
- This is a chemical change.
In summary, the boiling of water (option B) is a physical change, whereas the boiling of an egg, burning of cloth, and burning of paper (options A, C, and D) are all examples of chemical changes.