Page 98 - Chemistry_Form_2

Chemistry
for Secondary Schools

Combustion reactions are essential for energy production, heating, and
transportation, making them indispensable in everyday life. These reactions
release energy by burning fuels or materials, driving many practical applications.
Some processes related to combustion reactions include:
FOR ONLINE READING ONLY
(a) Burning of fuel: Burning fuel such as coal, oil, and natural gas is a combustion
reaction, where hydrocarbons react with oxygen to produce carbon dioxide,
water, and energy. For example, in the combustion of coal, carbon reacts
with oxygen to form carbon dioxide and heat energy.

(b) Cooking with gas stoves using natural gas (methane): Methane reacts with
oxygen to produce carbon dioxide, water and heat energy. Its combustion
reaction equation is:

The energy released heats the food during cooking.

(c) Candle burning: When a candle burns, the wax, usually made of paraffin (a
hydrocarbon), reacts with oxygen from the air, resulting in the production of
carbon dioxide, water, and heat.

(d) Respiration in living organisms: Cellular respiration is a slow combustion
reaction where glucose reacts with oxygen to release energy needed for body
functions.

Displacement reactions
A displacement reaction is a chemical reaction in which a more reactive element
displaces a less reactive element from its compound (Appendix 3). This reaction
is expressed in the general form as:

Two reactants yield two different products. For example, when zinc reacts with
hydrochloric acid, it displaces hydrogen to produce zinc chloride and hydrogen
gas.

Student’s Book Form Two 91

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