i)

Personal hygiene is the practice of keeping one's self/body and environment clean.

ii)

Ways by which personal hygiene could be maintained

1. Washing of hands with soap before preparing food, eating and after visiting the toilet
2. Fingernails and toenails should always be kept short and clean
3. Bathing frequently
4. Washing the hair frequently
5. Changing and washing of clothes frequently
6. Cleaning of teeth at least twice daily and preferably after each meal
7. Combs and hair brushes should not be shared
8. Drinking clean/treated water
9. Washing of hands after urinating
10. Cleaning the surroundings
11. Wearing of shoes and sandals to prevent cuts and infections

i)

A compound is the substance formed as a result of the chemical combination of two or more elements.

OR

A compound is a substance which is made up of two or more elements chemically combined.

Examples of compounds

1. Water/H₂O
2. Common salt/Sodium chloride/NaCl
3. Carbon dioxide/Carbon (IV) oxide/CO₂
4. Ammonia/NH₃
5. Cupric oxide/Copper (II) oxide/CuO
6. Sulphuric acid/H₂SO₄
7. Sodium hydroxide/NaOH
8. Ammonium chloride/NH₄Cl
9. Hydrochloric acid/HCl
10. Copper (II) sulphate/Copper (II) tetraoxosulphate (VI)/CuSO₄
11. Iron (II) chloride/FeCl₃
12. Magnesium chloride /MgCl₂
13. Iron (II) sulphide/FeS
14. Ammonium hydroxide/NH₄OH
15. Calcium carbonate/CaCO₃
16. Calcium chloride/CaCl₂
17. Silver chloride/AgCl
18. Sodium tetraoxosulphate (VI)/Na₂SO₄
19. Sodium nitrate/Sodium trioxonitrate (V)/NaNO₃
20. Potassium sulphate/Potassium tetraoxosulphate (VI)/K₂SO₄

ii)

A mixture is the substance formed as a result of the physical combination of two or more elements

OR

A mixture is formed as a result of the physical combination of two or more other substances which can be separated by physical means.

Examples of mixtures

1. Air
2. Salt solution
3. Sugar solution
4. Common salt and sand mixed together
5. Muddy water
6. Alcohol and water mixed together
7. Powdered charcoal and iron filings mixed together
8. Powdered chalk and water mixed together
9. Iodine and sand mixed together
10. Sodium chloride/common salt and sand mixed together
11. Sawdust and iron filings mixed together
12. Powdered charcoal and water mixed together
13. Brass
14. Bronze

i)

A machine is a device that makes work easier or faster

OR

A machine is a device which enables a small force (effort) to overcome a large force (load).

ii)

i)

A satellite is an object which moves around a planet in space

ii)

Uses of satellite

1. For exploring the planets/moons
2. For scientific research/experimental research/internet
3. To study the universe
4. For communications/broadcasting/telephone call
5. For weather forecast/collecting information on the weather
6. Map making
7. Spying
8. For navigation/satellite for navigation
9. Military purposes

i)

An ion is an atom/group of bonded atoms that has lost or gained electron(s) or a charged atom/group of bonded atoms

ii)

Methods of softening hard water

1. Boiling
2. Destillation
3. Addition of washing soda/Na₂CO₃/Sodium carbonate
4. Use of ion exchange resin/deionization

i)

Difference between pests and parasites

Pest is any organism which causes damage to crops/animals (beneficial to man) while a parasite is a living organism which lives on the surface/inside the body of another organism/host and gets its food from it and in so doing causing harm to the host.

ii)

Examples of pests and parasites

i)

Work is said to be done when a force moves a body through a distance in the direction of the force or is the product of force and distance moved in the direction of the force.

ii)

Work = Force x Distance

Force = 10 N
Distance = 5.2 m

Work done = 10 N x 5.2 m = 52 Joules(J)

(i)

Temperature of boiling water

100^o C or 373 K or 212^oF

(ii)

Nail 1 will fall off first followed by nail 2, 3 and 4 in that order.

(iii)

A will have the highest temperature followed by B then C and D will have the lowest temperature.

(iv)

Conduction

(v)

Effects of heat that is associated with the experiment

1. Heat transfer
2. Wax melts/water vaporizes
3. Expansion of metal/water
4. Decrease in density for metal/water
5. Water evaporates faster

(vi)

Aim of the experiment

To show that metals are good conductors of heat

OR

Heat travels through metals

(i)

To remove air/oxygen

(ii)

The oil on top of the water in set-up B is to prevent air/oxygen from dissolving back into the water.

(iii)

The purpose of the rubber stopper in set-up C is to prevent water/moisture from entering the test tube.

(iv)

The nail in set-up A rust because oxygen/air and water/moisture were present.

(v)

Aim for the experiment

To show that air/oxygen and water/moisture are necessary for rusting to take place.

(vi)

Oil or grease prevents air/oxygen and water/moisture from coming into contact with the metal for rusting to occur.

(i)

I → To kill the cells of the leaf/to stop all chemical reactions in the leaf
II → To decolorize the leaf/to remove the green pigment/chlorophyll from the leaf
III → To soften the leaf/remove or wash off alcohol from the leaf
IV → To test for the presence of starch in the leaf

(ii)

Leaf A changes from whitish/brownish to blue-black.

(iii)

Leaf A was in sunlight and therefore photosynthesis occurred but leaft B was in darkness so photosynthesis did not occur.

OR

Leaf A produced starch but leaf B did not produce starch.

(iv)

Aim for the experiment

To show that sunlight was necessary/important for photosynthesis/starch formation to occur.

i)

Fertilization is the fusion of the male and female sex cells to form a zygote.

ii)

The processes that lead to fertilization in humans after mating

1. The sperms move through the vagina, cervix and uterus to the fallopian tube
2. Only one of the millions of sperms succeeds to penetrate the membrane of the ovum
3. The nuclei of the sperm and ovum unit/fuse to form a zygote

i)

Density of a substance is the mass per unit volume of the substance.

OR

Density = $\frac{\mathrm{Mass\; (M)}}{\mathrm{Volume\; (V)}}$

ii)

Determination of the density of a stone

1. Measure/weigh the mass of stone by means of a beam/chemical balance as M g
2. Fill a large measuring cylinder with water to a suitable level and record the volume as V₁ cm³
3. Tie the stone with thread and gently lower it into the water in the measuring cylinder and record the new volume as V₂ cm³

The density of the stone is then calculated as follows:

Volume of stone = V₂ cm³ - V₁ cm³

Mass of stone = M g

Density = $\frac{\mathrm{Mass}}{\mathrm{Volume}}$

Density of the stone = $\frac{\mathrm{M\; g}}{({\mathrm{V}}_2-{\mathrm{V}}_1){\mathrm{cm}}^3}$

i)

An element is a substance that cannot be broken down/split into simpler substances by any known chemical means.

ii)

(i)

The process by which green plants manufacture their food is called photosynthesis

(ii)

Factors necessary for photosynthesis

1. Chlorophyll/green matter in the leaf
2. Sunlight/light
3. Water (H₂O)
4. Mineral salts
5. Carbon dioxide/Carbon (IV) oxide/ (CO₂)
6. Suitable temperature

(i)

Devices that could be used to carry a heavy body onto a truck

1. Inclined plane
2. Pulley
3. Crane
4. Lifting magnets/Electromagnet
5. Forklift

(ii)

Simple levers used in everyday life

1. Wheel barrow
2. Can opener
3. A pair of scissors
4. Nutcrackers
5. Forceps
6. Sugar tong
7. Bottle opener
8. Crowbar
9. Claw hammer
10. A pair of pliers
11. Knife
12. Paper cutter
13. A pair of pincers
14. See saw

(iii)

Note: any of the above diagrams represents labelled lever.

(i)

General preparation of ammonia gas

1. Ammonia gas can be prepared by heating powdered ammonium chloride and sodium hydroxide/calcium hydroxide
2. The ammonia gas produced is dried by passing it through calcium oxide

(ii)

Chemical equation for the preparation of ammonia gas

NH₄Cl + NaOH → NaCl + H₂O + NH₃

OR

2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2H₂O + 2NH₃

(i)

In the depths of the ocean where it is always dark, there are no green plants

Light does not get to those depths and therefore photosynthesis cannot occur there.

(ii)

On an island where there are no insects and birds, the pawpaw plant produces only flowers but no fruits

Insects and birds transfer pollen grains for pollination of pawpaw flowers and in their absence fertilization does not occur and there is no fruit formation.

OR

Insects and birds are agents of pollination/transfer pollen grains. In their absence no fertilization and no fruit formation occur.

(i)

Laws of reflection

1. The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane
2. The angle of incidence is equal to the angle of reflection

(ii)

A labelled diagram to show the reflection of light on a plane mirror