i)

I → Crown or Enamel
II → Dentine
III → Cement or Periodontal membrane
IV → Jaw bone or Root
V → Pulp Cavity

ii)

Functions of I (Crown or Enamel)

1. Protect teeth from harmful bacteria
2. Enables teeth withstand pressure of chewing
3. Cutting/chewing/protect dentine/protect pulp cavity

Functions of III (Cement or Periodontal membrane)

Holds tooth firmly in socket or jaw bone or supports the tooth

iii)

The part affected by tooth decay is V (Pulp Cavity)

iv)

Prevention of Tooth decay

1. Avoid using sharp-pointed objects
2. Avoid having dry mouth
3. Use water containing flourides to wash teeth/mouth
4. Avoid smoking
5. The teeth should be cleaned regularly after each meal/remove food particles from the teeth/flossing
6. Wash the mouth vigorously after each meal
7. Regular visit the dentist
8. Avoid eating too hot food
9. Avoid eating too much sugary food
10. Avoid eating too cold food

i)

The phenomenon illustrated is refraction of light

ii)

I → Normal
II → Incident ray
III → Angle of incidence
IV → Angle of refraction
V → Refracted ray

iii)

Why object appears closer to surface

Rays from the object at the bottom are bent away from the normal as they come out of the water. In a straight line, these rays appear to come from a point above the bottom

i)

I → Retort/clamp stand
II → filter paper
III → funnel

ii)

Function of II (Filter paper)

1. To filter solid or insoluble particles or residue
2. To separate the mud,solid or insoluble particles from the water
3. To prevent residue/solid/insoluble particles/mud from entering the filtrate

iii)

Name of filtrate is water

iv)

Physical properties of filtrate (Water)

1. It has a density of 1 gcm^-3 or 1000 kg m^-3
2. It boils at 100 ^oC
3. It freezes at 0 ^oC (at 1 atm)
4. It is colourless
5. It is tasteless or insipid
6. It is odourless
7. It has a high surface tension
8. It is a universal solvent
9. It is transparent
10. It has a neutral pH or pH of 7
11. It exists in three states (solid, liquid and gas)

v)

Other materials that could be used instead of filter paper

1. Cotton wool
2. Foam
3. Glass wool
4. Clean/white cloth

i)

Process likely to occur is erosion

ii)

Farming practices that could lead to the process occuring (erosion)

1. Bush burning
2. Deforestation
3. Continuous cropping
4. Crop removal
5. Excessive use of chemicals or inorganic fertilizers
6. Overgrazing
7. Cultivating or ploughing along slope

iii)

Farm practices that could control the process (erosion)

1. Planting cover crops
2. Terracing
3. Cultivating or ploughing slope or contour
4. Heavy mulching
5. Construction of drainage channels
6. Planting trees beside farm
7. Strip cropping
8. Contour bunding

iv)

Soil resources depleted

1. Soil organisms
2. Nutrients
3. Mineral matter
4. Soil particles or mineral matter
5. Growing crops
6. Air
7. Organic matter or humus

(i)

Stages in the life-cycle of a mosquito

1. Egg
2. Larva
3. Pupa
4. Adult

(ii)

Stage at which feeding does not take place

Pupa

(i)

Magnetic pole

Point/area on a magnet where the magnetic force is greatest or where all lines of force appear to enter.

(ii)

Uses of temporary magnets

1. Loudspeaker
2. Electric bell
3. Telephone earpiece
4. Generators/electric motors

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)

Classes of food

1. Carbohydrates
2. Proteins
3. Fats and oils
4. Vitamins
5. Mineral salts
6. Water

(ii)

Starch → Carbohydrate
Milk → Protein
Margarine → Fat and oil
Sugar → Carbohydrate

(i)

calcium hydroxide → Ca(OH)₂

(ii)

zinc chloride [zinc (II) chloride] → ZnCl₂

(iii)

sodium nitrate [sodium trioxonitrate (V)] → NaNO₃

(iv)

calcium carbonate [calcium trioxocarbonate (IV)] → CaCO₃

(v)

potassium sulphate [potassium tetraoxosulphate (VI)] → K₂SO₄

(i)

Viscosity is defined as the internal force that opposes the movement of liquid molecules.

(ii)

An experiment to compare the viscosities of two liquids A and B

1. Liquid A and B are both poured into two separate identical measuring cylinders to the same level
2. Two identical metal balls are dropped into each of the measuring cylinders and the time taken for each ball to reach the bottom/base of the cylinders of liquids A and B are recorded
3. The liquid in which the metal ball took a longer time to reach the base/bottom of the measuring cylinder is more viscous

i)

Soil erosion is the washing away/removal of the top soil by water or wind

ii)

Methods of controlling soil erosion

1. Terracing
2. Strip cropping
3. Contour ploughing
4. Wind breaks/afforestation/tree planting
5. Mulching
6. Cover cropping
7. Practising crop rotation
8. Bush fallowing/land rotation

α)

Adaptation is the ability of an organism to survive in a given environment using special features

β)

Endangered species are plants and animals facing extinction/numbers are decreasing.

i)

Examples of hard water

1. Well water
2. Sea water/lagoon water
3. Borehole

ii)

Why it is advisable to drink hard water

1. It contains ions of calcium which are good for strong bones and teeth
2. It helps to reduce heart ailments

i)

Magnetic field is the area around a magnet where the effect of the force of a magnet can be felt/experienced.

ii)

Methods of making magnets

1. Hammering/strong heating in the earth's magnetic field
2. Stroking
3. Electrical
4. Induction

(i)

I → Cell/battery
II → Key/switch
III → Ammeter
IV → Lamp/bulb
V → Rheostat/variable resistor
VI → Voltmeter

(ii)

II/Key/Switch

(iii)

The lamp (IV) will light

OR

The ammeter (III) will deflect

OR

The voltmeter (VI) will deflect

(iv)

Chemical energy (of cell) → Electrical energy (in wires) → Light/heat energy (in bulb)

(v)

Parallel connection

(i)

Distillation/Fractional distillation

(ii)

Y → Alcohol because it has a lower boiling point than water/it boils off/evaporates first before water.

(iii)

Function of the thermometer

Is used to note/measure/determine the temperature (at which the mixtures boil/separate)

OR

It is used to note/measure/determine the boiling points of the mixtures

Function of the water jacket X

It is used to condense/cool the vapour

(iv)

Liquid →heat Vapour →cool Liquid

OR

Heating → Vaporisation → Condensation

(v)

Water and alcohol have different boiling points.

(i)

A → Starch
B → Oil/Fat/Lipid
C → Reducing/simple sugar/glucose

(ii)

A (Starch) → Glucose/fructose
B (Oil/Fat/Lipid) → Fatty acids/glycerol
C (Reducing/simple sugar/glucose) → Glucose/No digestion occurs/remains the same

(iii)

A → Mouth
B → Duodenum/small intestine
C → Not digested/passes through the system

(iv)

C (Reducing/simple sugar/glucose) is absorbed in the small intestine (ileum)