Correct Option
The correct option is (d).
Explanation
A chemical change is a process where one or more substances are transformed into new substances with different chemical properties. Unlike physical changes, chemical changes involve the breaking and making of chemical bonds and are generally irreversible.
Statement-wise Analysis
- 1. Photosynthesis: Correct. This is a biochemical process where green plants synthesize nutrients from carbon dioxide and water in the presence of sunlight and chlorophyll. New substances (glucose and oxygen) are formed, making it a chemical change.
- 2. Digestion of food: Correct. Digestion involves the breakdown of complex food molecules (carbohydrates, proteins, fats) into simpler substances (glucose, amino acids, fatty acids) through the action of enzymes and acids. Since the chemical composition of the food changes, it is a chemical change.
- 3. Fermentation of grapes: Correct. Fermentation is a metabolic process where enzymes (often from yeast) convert sugars into alcohol (ethanol) and carbon dioxide. This results in the formation of entirely new chemical compounds.
- 4. Ripening of fruits: Correct. Ripening involves a series of chemical reactions, such as the breakdown of starch into sugars and the degradation of chlorophyll. These reactions alter the taste, texture, and color of the fruit permanently, constituting a chemical change.
Key Takeaway: Any process that results in the formation of new substances with distinct chemical identities and cannot be easily reversed by physical means is classified as a chemical change.