(i)

A compound is a substance which contains two or more elements chemically combined and cannot be separated by any physical method.

Examples of compounds

1. Water/H₂O
2. Common salt/Sodium chloride/NaCl
3. Carbon dioxide/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/Carbon (IV) oxide/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)

An element is a pure substance made up of atoms of the same kind.

OR

An element is chemically a simplest substance that cannot be broken down into any simpler form by any known chemical means.

Examples of elements (First 20 elements)

(i)

Differences between electrical insulators and electrical conductors

(ii)

A simple electrical circuit made up of a cell and a switch connected to two electric bulbs connected in parallel

i)

Hazard is a danger/risk that could result in physical harm to people/damage to property or is any source of potential damage/harm/adverse health effect on something/someone.

ii)

Precautions against hazard

1. Wearing of protective clothing/boots/goggles
2. Routine maintenance of equipment
3. Closing all taps before leaving the laboratory
4. Switching off all electrical points
5. Mounting hazard signs of dos and don'ts in the laboratory/working area etc.
6. Avoid skin and eye contact with chemicals
7. Use equipment only for its designated purpose
8. All containers must have appropriate labels. Unlabeled chemicals should never be used
9. Do not taste or intentionally sniff chemicals
10. Never consume and/or store food or beverages or apply cosmetics in areas where hazardous chemicals are used or stored
11. Wash exposed areas of the skin prior to leaving the laboratory
12. Do not work alone in a laboratory if the procedures being conducted are hazardous

i)

Weather is atmospheric conditions at a place over a short duration of time or day to day conditions/changes of the atmosphere/environment

ii)

Differences between weather and season

i)

Fertilse soil is a soil that has an abundance of plant nutrients/minerals organic matter to support plant growth or it contains all the major nutrients for basic plant nutrition as well as other to support plant growth.

ii)

Causes of loss of soil fertility

1. Loss of top soil by erosion
2. Nutrient mining/depletion/removal of nutrients by crops
3. Sand winning/physical degradation of soil/poor soil structure/water logging/compaction
4. Decreased soil bioactivity
5. Soil acidification/salinization/alkalization
6. Leaching
7. Overgrazing
8. Overcropping
9. Soil erosion
10. Excessive burning/bush burning/wildfires
11. Soil pollution/indiscriminate use of agrochemicals
12. Inefficient soil management practices

(i)

Separation of common salt and sand

1. Dissolve the common salt by adding water to the mixture in a beaker
2. Stir the mixture
3. Filter the sand from the salt solution using filter paper in a funnel
4. Using a Bunsen burner, heat the salt solution to retrieve the salt in an evaporating dish

(ii)

Separation of muddy water

1. Fold a filter paper into a funnel
2. Pour the muddy water into the funnel and filter
3. The water is then collected by a beaker and sand is left on the filter paper

i)

ii)

Common solvent used in the home

1. Water
2. Alcohol
3. Turpentine
4. Kerosene
5. Petrol

i)

Ration is the amount/quantity of food allowed an animal for a day/specific period of time.

ii)

Dehorning is the removal of the horns of animals to reduce fighting among them.

i)

An element is a substance that is made up of atoms of the same kind.

OR

An element is a substance that cannot be broken down into any simplier form (by any known chemical means).

ii)

i)

Mixed farming is a type of farming in which animals and plants are produced on the same piece of land at the same time.

ii)

Mixed cropping is the cultivation of more than one type of crop on the same piece of land at the same time.

(i)

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

(ii)

Types of pollution

(i)

Vegetative reproduction is a form of reproduction whereby plants produce young ones from growing parts/buds of the parent plant.

(ii)

Examples of plants that reproduce vegetatively

1. Potato
2. Yam
3. Cocoyam
4. Canna lily
5. Onion
6. Plantain
7. Banana
8. Ginger
9. Pineapple
10. Bryophyllum
11. Sugar cane
12. Cassava
13. Fern
14. Elephant grass
15. Tiger nuts
16. Garlic

(i)

Parts of an atom and their electrical charges

(ii)

Work is said to be done when the point of application of a force moves an object through a distance in the direction of the force.

OR

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

OR

Work is the product of force and the distance moved in the direction of the force.

OR

Work = Force x distance moved in the direction of the force

(iii)

Differences between heat and temperature

Heat is the energy which causes rise in temperature of bodies while temperature is the degree of hotness or coldness of a body.

The unit of heat is joules and temperature is kelvin or degree celsius

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