The chemical changes are: a. growth of a plant, b. rusting of iron, d. cooking of food, e. digestion of food, and g. burning of a candle.
Explanation: A chemical change occurs when the composition of a substance changes, creating a new substance with different properties.
Growth of a plant:
Plants undergo complex chemical reactions like photosynthesis to produce organic compounds, thus changing their composition.
Rusting of iron:
Iron reacts with oxygen and moisture to form iron oxide (rust), a new chemical compound.
Cooking of food:
Heat alters the chemical structure of food proteins and carbohydrates, creating new flavors and textures.
Digestion of food:
Enzymes break down complex food molecules into simpler ones that can be absorbed by the body, a chemical process.
Burning of a candle:
Wax undergoes a combustion reaction, breaking down into carbon dioxide and water vapor.
Why “c. mixing of iron filings and sand” is not a chemical change:
Mixing iron filings and sand is a physical change because the substances remain separate and their individual chemical compositions do not change.