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)

ii)

Work done = Force x Distance

Force = Mass x Acceleration due to gravity (g)

Mass = 80 kg
g = 10 ms^-2

Force = 80 kg x 10 ms^-2 = 800 N

Distance = 5 m

Work done = 800 N x 5 m = 4000 J

i)

Characteristics of an insect pollinated flower

1. Petals are large
2. Petals are brightly coloured
3. The flower is usually scented
4. The flower has nectar
5. Stigma is inside the flower
6. Stigma is compact and sticky
7. Pollen grains produced per anther are few
8. Pollen grains are sticky, large, rough and heavy
9. Filaments are short and stout

ii)

Characteristics of a wind pollinated flower

1. Have less brightly coloured petals/petals are dull in colour
2. Petals are small in sizes and not easily seen or absent
3. The flower lacks nectar
4. The flower is not scented
5. Large amount of pollen grains are produced per anther
6. Have feathery/hairy stigma
7. Stigma hangs down to be able to catch pollen grains floating in the air
8. Pollen grains are small, light or dry and smooth
9. Filaments are long and flexible

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)

An alloy is a uniform/homogenous mixture of two or more metals or a metal and non-metal.

ii)

Diffusion is the process whereby molecules/particles of a liquid/gas move from a region of higher concentration to a region of a lower concentration until they are uniformly spread throughout an occupied space.

iii)

A colloid is a suspension in which the suspended particles are very small in size but bigger than the molecules of the solvent and are permanently suspended/does not settle on standing.

i)

Examples of alloy

1. Bronze
2. Brass
3. Steel
4. Solder
5. Duralumin
6. Cupronickel

ii)

Examples of colloid

1. Emulsion paint
2. Fog
3. Smoke
4. Milk
5. Toothpaste
6. Mist
7. Soap lather
8. Clay in water
9. Chalk in water
10. Gel
11. Aerosols

i)

Pollution is the release of toxic/harmful/poisonous substances into the environment.

ii)

i)

Potential energy

ii)

Potential Energy = Mass (m) x Acceleration due to gravity (g) x Height (h)

Weight = Mass x Acceleration due to gravity

Potential Energy = Weight x Height

Weight = 50 N
Height = 15 m

Potential Energy = 50 N x 15 m = 750 J