Which of the following are chemical changes?
(i) digestion of food
(ii) liquefaction of air
(iii) ripening of fruit
(iv) dissolution of sulfur in carbon disulfide
(v) freezing of water
(vi) electrolysis of water
(i) to (iv) all
(i), (iii), (v)
(i), (iii), (vi)
(iii), (iv), (vi)
Which of the following are chemical changes?
(i) digestion of food
(ii) liquefaction of air
(iii) ripening of fruit
(iv) dissolution of sulfur in carbon disulfide
(v) freezing of water
(vi) electrolysis of water
(i) to (iv) all
(i), (iii), (v)
(i), (iii), (vi)
(iii), (iv), (vi)
The correct option is C (i), (iii), (vi)
Solution:
Physical change:
A physical change is a temporary and easily reversible change in which the physical properties (e.g., physical state, shape, size, appearance, density, etc.) of a substance change.
Chemical change:
A chemical change is a permanent change in which the chemical composition of a substance is changed, and one or more new substances with different chemical compositions and different properties are formed and the change is not easily reversible.
(i) Digestion of food is considered a chemical change because enzymes in the stomach and intestines break down large macromolecules into simpler molecules so that the body can more easily absorb the food.
(ii) Liquefaction of air: Air is liquefied by the Linde process, in which air is alternately compressed, cooled, and expanded, each expansion results in a considerable reduction in temperature, with the lower temperature, the molecules move more slowly and occupy less space, so the air changes phase to become liquid and this is a physical change because physical change affecting the form of a chemical substance but not it's chemical composition.
(iii) Ripening of fruit: During the process of ripening, the pigment present in the skin of the fruit changes, and this cannot be reversed back. Ripening of fruit is a chemical change because the fruit reacts with the atmosphere and gets ripen so a chemical change is involved.
(iv) Dissolution of sulfur in carbon disulfide: It is a physical change because on dissolving sulfur to the carbon disulfide no formation of a new compound takes place so it is not a chemical change.
(v) Freezing of water: Freezing is the withdrawal of heat from a substance to change that substance from a liquid to a solid. The temperature must be below or at the substance's freezing point for the change to occur. Freezing of water is a example physical change because water molecules remain as water molecules only.
(vi) Electrolysis of water: Electrolysis of water is a chemical process as it involves the conversion of water to 'hydrogen and oxygen where we cannot change them to water, and there is a chemical bond 'breaking' and 'formation' of different bonds happen, so it's considered as a chemical change.
Hence, digestion of food, ripening of fruit, and electrolysis of water are chemical changes.
Final answer:
Hence, Option (C) is correct.
(i), (iii), (vi)
Solution:
Physical change:
A physical change is a temporary and easily reversible change in which the physical properties (e.g., physical state, shape, size, appearance, density, etc.) of a substance change.
Chemical change:
A chemical change is a permanent change in which the chemical composition of a substance is changed, and one or more new substances with different chemical compositions and different properties are formed and the change is not easily reversible.
(i) Digestion of food is considered a chemical change because enzymes in the stomach and intestines break down large macromolecules into simpler molecules so that the body can more easily absorb the food.
(ii) Liquefaction of air: Air is liquefied by the Linde process, in which air is alternately compressed, cooled, and expanded, each expansion results in a considerable reduction in temperature, with the lower temperature, the molecules move more slowly and occupy less space, so the air changes phase to become liquid and this is a physical change because physical change affecting the form of a chemical substance but not it's chemical composition.
(iii) Ripening of fruit: During the process of ripening, the pigment present in the skin of the fruit changes, and this cannot be reversed back. Ripening of fruit is a chemical change because the fruit reacts with the atmosphere and gets ripen so a chemical change is involved.
(iv) Dissolution of sulfur in carbon disulfide: It is a physical change because on dissolving sulfur to the carbon disulfide no formation of a new compound takes place so it is not a chemical change.
(v) Freezing of water: Freezing is the withdrawal of heat from a substance to change that substance from a liquid to a solid. The temperature must be below or at the substance's freezing point for the change to occur. Freezing of water is a example physical change because water molecules remain as water molecules only.
(vi) Electrolysis of water: Electrolysis of water is a chemical process as it involves the conversion of water to 'hydrogen and oxygen where we cannot change them to water, and there is a chemical bond 'breaking' and 'formation' of different bonds happen, so it's considered as a chemical change.
Hence, digestion of food, ripening of fruit, and electrolysis of water are chemical changes.
Final answer:
Hence, Option (C) is correct.
