CHAPTER 4: COMMBUSTION – SCIENCE STANDARD FOUR NOTES

CHAPTER 4: COMMBUSTION – SCIENCE STANDARD FOUR NOTES

Explain the concept of combustion

Combustion is the chemical reaction involves the burning of a substance in the presence of oxygen to produce heat and light.

• Material which catch fire and burn easily is called combustible
• Examples of combustible materials are Wood
• Wood
• Cooking gas
• Cloth
• Charcoal
• Petroleum
• Enclosed space (closed system) in which combustion takes place, especially in an engine or furnace is called combustion chamber
• Different material are combustible but some burn up faster than others

Application of combustion (Effects of combustion)

It’s applied in many areas, includes Industries

1. i. Engine or furnace
2. In large boilers
3. Incinerators for burning wasters
4. welding and smelting (extract metal) Domestic
5. v. Cooking
6. vi. Heating homes
7. vii. Burning wastes Laboratory
8. viii. Sterilization
9. ix. During experiments

Make simple scientific observations

Investigate life cycle of insect vectors

(b)Action which destroy insects which transmit diseases

• Some insects are useful and others are harmful.
• In order to understand the insect properly, we have to study their growth and development.
• The growth and development of an insect is called metamorphosis.
• Insects undergo two types of metamorphosis,
• Complete metamorphosis and,
• Incomplete metamorphosis.

Complete metamorphosis:

• It is a developmental growth where the insect undergoes four stages in their life cycle.
• A female adult lays egg.
• The eggs hatch into a larva (singular larva).
• The larvae then change into pupae (singular pupa).
• The pupa is called resting stage because it does not feed.
• The pupa now develops into an adult insect (imago).

Examples of insects that undergo complete metamorphosis include;

1. Mosquitoes,
2. Butterfly
3. Houseflies,
4. Honeybees,
5. Tsetse fly.

In short form MOBUHOBE

Insect	Egg	Larva	Pupa	Adult insect (imago)
Butterfly Mosquito Housefly Honeybees	Egg Egg Egg Egg	Caterpillar Wrigglers Maggots Grub	Chrysalis Pupa Pupa Pupa	Adult Butterfly Adult Mosquito Adult Housefly Adult Honeybees

INCOMPLETE METAMORPHOSIS:

• Incomplete metamorphosis is a kind growth where an insect undergoes three stages of growth in its life cycle, i.e.

Egg Nymph Adult

• The eggs hatch into a nymph which looks like the adult insect.
• The insects which undergo incomplete metamorphosis include;
• Cricket
• Cockroach
• Locust,
• Grasshoppers etc.
• In short form is (CRICOLGRA)

Exercise

1. Write two insects that undergo a complete metamorphosis

2. Write insects which spread the following diseases:

a) Elephantiasis

b) Sleeping sickness

c) Malaria

d) Yellow fever

IMPORTANCE OF INSECTS

1. Sources of food – some insects like locust, grasshopper and termites are a good source of protein to human beings.
2. Pollination – insect are good agents of pollination. Farmers keep honeybees in their arms to aid in pollination of their crops.
3. Other insects like ants, and termites aerate and decompose dead materials in the soil, making it fertile for farming.
4. Source of income -farmers keep honeybees which produce honey and wax for commercial purposes, hence generating income.

HARMFUL EFFECTS OF INSECTS

1. Some insects are destructive to vegetation e.g. locust and butterfly larva (caterpillar).
2. Other insects like bees, wasp and black ants produce poisonous sting.
3. Other insects cause damage to human property e.g. termites destroy wooden furniture, timber and other useful equipment leading to enormous losses.
4. Some insects are vectors. Vectors are organisms which carry and spread the disease-causing organisms (germs).

CHAPTER 4: COMMBUSTION – SCIENCE STANDARD FOUR NOTES

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