Page 149 - Primary Five Science

2. Chemical changes

These are changes where the substance formed is com-

pletely different. These are changes that are irreversible:

Examples of chemical changes

 Burning wood to ash, Rusting, Digestion, Fermenta-

tion, Weathering of rocks, Rotting, Respiration, Boiling

of an egg, Decomposition

Characteristics of Chemical changes

 New substance with different composition are

produced

 The change is not easily reversed

 Chemical and Physical properties of the sub-

stance change

 There is change in mass of final product

Example of chemical changes include;

 Food digestion: The body changes food to glucose

and other substances.

 Combustion or burning of substances.

 Rusting of metals

 Photosynthesis by green plants. Plants change carbon dioxide,
water and light to glucose
Camouflage or mimicry in ani-
 Respiration; Use of Oxygen and glucose to form energy

Shading of leaves in dry season  Dissolving of substances such as salt and water

 Fermentation and decay

 Souring of milk