Question

Classify the changes involved in the following processes as physical or chemical changes.
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Bumping of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f) Digestion of food.

Answer 1

Hint:Physical changes are only responsible for changes in the physical properties of the substance and are also reversible. Chemical changes are only responsible for changes in the composition or the structure and are also irreversible in nature.

Complete step-by-step answer:As discussed in hint, Physical changes are only responsible for changes in the physical properties of the substance and are also reversible. Chemical changes are only responsible for changes in the composition or the structure and are also irreversible in nature.

(a) Photosynthesis:
      As it is irreversible, so it comes under chemical change.
(b) Dissolving sugar in water:
      It is reversible, hence physical change.
(c) Bumping of coal:
      It is irreversible, therefore chemical change.
(d) Melting of wax:
      It is reversible by cooling, so physical change.
(e) Beating aluminium to make aluminium foil:
      It is physical change as malleability (beating metal into thin sheets) does not really change composition.
(f) Digestion of food:
      It is a chemical change.

Additional Information:
Chemical changes occur whenever a substance is combined with another to produce a new substance, known as chemical synthesis or, also, chemical decomposition into 2 or more different substances. These processes are known as chemical reactions and, generally, are not actually reversible except by further chemical reactions.
A physical change is actually a change to the physical properties, as opposed to chemical properties of a substance. They are generally reversible in nature. The physical properties of a substance involve characteristics such as shape (volume and size), colour, texture, flexibility, density, and mass.

Note:As discussed in the hint, a physical change is actually a change to the physical properties while chemical changes are only responsible for changes in the composition or the structure. Based on their nature, options can be categorized.