(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)

Density is the mass per unit volume of a substance

OR

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

(ii)

Determination of the density of 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)

Alcohol and water → Distillation/fractional distillation

(ii)

Salt and water → Distillation/Evaporation and condensation

(iii)

Powdered charcoal and iron filings → Use of magnet

(iv)

Powdered chalk and water → Filtration/decantation

i)

Aerobic respiration is the process of cellular respiration that takes place in the presence of oxygen gas to produce energy from food.

OR

Aerobic respiration is the breakdown/oxidation of organic food substance/glucose in the presence of oxygen to release large amount of energy, water and carbon dioxide as by-products.

ii)

Aerobic respiration requires oxygen while anaerobic respiration does not require oxygen.

OR

In aerobic respiration oxygen is used while in anaerobic respiration oxygen is not used.

i)

Potential difference also known as voltage, is the external work needed to bring a charge from one location to another location in an electric field.

OR

Is the work done in moving a unit of positive electric charge from one point to another.

ii)

Potential Difference (V) = Current x Resistance

V = IR
Where V = potential difference, I = current and R = resistance

Potential difference = 250 V
Resistance = 100 Ω

250 = I x 100

Divide both sides by 100 to solve for I.

I = $\frac{250}{100}$ = 2.5 A

The current flowing through the resistor is 2.5 A

i)

Cocoa

ii)

Causative organism of the swollen shoot disease

Virus/Cacoa swollen shoot virus

iii)

Method of spread of the swollen shoot disease

Virus transmitted by nymphs of mealy bugs from infected plant to healthy plants.

iv)

Ways of preventing the spread swollen shoot disease

1. Destroy infected trees
2. Regular inspection of seedlings/planting materials
3. Use of quarantine/cordin sanitaire (leaving 10m wide cocoa free zone around area
4. Barrier cropping
5. Using partly tolerant hybrids/using resistant varieties
6. Removing host free species

i)

Electronic configuration for Y = 2:7

ii)

X⁺/L⁺

Note: The ion formed is cation. It can lose the one electron in its last shell to be make it more stable with only two electrons.

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)

Physical properties of water

1. Odourless
2. Colourless
3. Tasteless/insipid
4. Freezes at 0^oC
5. Boils at 100^oC
6. Universal solvent
7. Exists in three states
8. Has a density of 1g/cm³ (at 4^oC)
9. It is transparent
10. It has a neutral pH/pH = 7
11. High surface tension

ii)

Why water is neutral

When red litmus paper or blue litmus paper is dropped in a sample of water, there is no change in colour.

i)

Functions of nitrogen in plants

1. For plant growth/vegetative growth
2. Increases yield of straw
3. A constituent of organic compound of plants
4. For plant development
5. Increases seed and fruit production
6. To make proteins
7. To make chlorophyll

ii)

Functions of potassium in plants

1. Plays an important role in plant metabolism
2. Plays an important role in translocation of starch to growing parts
3. Plays an important role in carbohydrate formation
4. Neutralization of organic acids
5. Strengthens straw and stalk of plants
6. Aids absorption of nutrients
7. Helps to reduce diseases in plants
8. Helps to produce quality fruit and promotes seed development
9. Activates enzymes for photosynthesis and respiration
10. Helps build proteins
11. Aids absorption of nutrients

i)

Human activities that disrupt the carbon cycle

1. Destruction of forest/cutting of trees/lumbering
2. Bush burning
3. Burning of fossil fuels

ii)

Effects of the disruption of the carbon cycle on the environment

1. Global warming/rise in temperature/greenhouse effect/affects climate
2. Reduction in oxygen
3. Rise in sea level/flooding/melting of ice
4. Animals/plants become endangered/extinct
5. Prolonged drought
6. Reduction in rainfall

i)

Density is the mass per unit volume of a body

OR

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

ii)

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

Density x Volume = Mass

Divide both sides by Density

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

Mass = 50 kg
Density = 2kg/m³

Volume = $\frac{50}{2}$ = 25 m³

(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