Which of the following is not a physical change?(a) Boiling of water to give water vapour(b) Melting of ice to give water(c) Dissolution of salt in water(d) Combustion of Liquefied Petroleum Gas (LPG

The answer is (d) Combustion of Liquefied Petroleum Gas (LPG).

Here's why:

(a) Boiling of water to give water vapour: This is a physical change because it's a change in the state of matter (from liquid to gas), but the substance itself (water) remains the same.

(b) Melting of ice to give water: This is also a physical change because it's another change in the state of matter (from solid to liquid), but the substance itself (water) remains the same.

(c) Dissolution of salt in water: This is a physical change because the salt is simply dissolving into the water, not chemically reacting with it. The salt can be recovered by evaporating the water.

(d) Combustion of Liquefied Petroleum Gas (LPG): This is not a physical change, but a chemical change. Combustion is a chemical reaction, specifically an exothermic reaction (it releases heat). In this case, the LPG reacts with oxygen in the air to produce heat, light, carbon dioxide, and water. The original substances (LPG and oxygen) are transformed into new substances (carbon dioxide and water).

The answer is (d) Combustion of Liquefied Petroleum Gas (LPG).

Here's why:

(a) Boiling of water to give water vapour: This is a physical change because it's a change in the state of matter (from liquid to gas), but the substance itself (water) remains the same.

(b) Melting of ice to give water: This is also a physical change because it's another change in the state of matter (from solid to liquid), but the substance (water) remains the same.

(c) Dissolution of salt in water: This is a physical change because the salt is not chemically altering the water or being chemically altered by the water. It's simply being dispersed evenly throughout the water.

(d) Combustion of Liquefied Petroleum Gas (LPG): This is not a physical change, but a chemical change. Combustion is a chemical reaction, specifically an exothermic oxidation-reduction reaction. When LPG burns, it reacts with oxygen to produce heat, light, carbon dioxide, and water vapor. This is a change in the chemical composition of the substance, not just a change in its physical state or appearance.

To determine which of the given options is not a physical change, we need to understand the difference between physical and chemical changes.

A physical change refers to a change in the physical properties of a substance, such as its shape, size, or state, without altering its chemical composition. On the other hand, a chemical change involves a transformation at the molecular level, resulting in the formation of new substances with different chemical properties.

Let's analyze each option:

(a) Boiling of water to give water vapor: This is a physical change. When water is heated, it changes from a liquid state to a gaseous state, but its chemical composition remains the same.

(b) Melting of ice to give water: This is also a physical change. When ice is heated, it melts and changes from a solid state to a liquid state, but its chemical composition remains unchanged.

(c) Dissolution of salt in water: This is a physical change as well. When salt is added to water, it dissolves and forms a homogeneous mixture. The salt molecules are dispersed throughout the water, but their chemical composition remains the same.

(d) Combustion of Liquefied Petroleum Gas (LPG): This is a chemical change. Combustion involves the reaction of LPG with oxygen, resulting in the release of heat, light, and the formation of new substances, such as carbon dioxide and water vapor. Therefore, option (d) is not a physical change.

In conclusion, the correct answer is (d) Combustion of Liquefied Petroleum Gas (LPG).