(i)

Elements on the periodic table

I → Hydrogen
II → Sodium
III → Beryllium
IV → Magnesium
V → Aluminium
VI → Helium

(ii)

(iii)

Note: the groups are the verticals

I (Hydrogen) → Group 1
II (Sodium) → Group 1
III (Beryllium) → Group 2
IV (Magnesium) → Group 2
V (Aluminium) → Group 13
VI (Helium) → Group 18

(iv)

Note: the periods are the horizontals

I (Hydrogen) → Period 1
II (Sodium) → Period 3
III (Beryllium) → Period 2
IV (Magnesium) → Period 3
V (Aluminium) → Period 3
VI (Helium) → Period 1

(v)

II (Sodium)

(v)

IV (Magnesium)

(i)

I → Egg(s)
II → Larvae
III → Pupa
IV → Adult

(ii)

Activities of the housefly that affect humans

1. They transfer diseases (such as dysentery)
2. They cause food poisoning
3. They are nuisance in the environment

(iii)

How the activities stated in (ii) can be reduced

1. Sanitation: Flies can be controlled by keeping the environment clean such as Keeping trash cans clean and tightly covered
2. Exclusion: They can be kept outside of homes by the use of window and door screens
3. Non-chemical Measures: The use of such devices as ultraviolet light traps, sticky fly traps, fly swatters, baited fly traps, etc. can eliminate flies from inside a home
4. Chemical Control: Spray with/use of insecticides to kill the housefly

(i)

Experiment to demonstration the dispersion of light

(ii)

I → Light/Source of light/white light/sunlight/bulb light
II → Glass prism
IiI → White screen

(iii)

IV → colour red/red
V → colour orange/orange
VI → colour yellow/yellow
VII → color green/green
VIII → colour blue/blue
IX → colour indigo/indigo
X → colour violet/violet

Note: ROYGBIV is used to memorize the order/sequence of dispersion of light

(i)

I → Egg(s)
II → Nymph
III → Adult

(ii)

Activities of the grasshopper that affect humans

1. It facilitates plant decomposition and regrowth
2. It fertilizes the soil through its excrete waste
3. It is a vital source of food for predators which help in maintaining the structure of the ecosystem
4. It causes damage to crops/destroys crops or other vegetations
5. Serves as food/delicacy or source of protein for some people

(iii)

How the activities of the grasshopper can be reduced

1. Practicing crop rotation
2. Hand picking and killing them
3. Setting up traps such as sticky traps
4. Spraying insecticides
5. Keeping predators such as poultry/birds to feed on them

(i)

The pH scale measures how acidic an object is. Objects that are not very acidic are called basic. The scale has values ranging from zero (the most acidic) to 14 (the most basic)

(ii)

The range of a pH scale is from 0 to 14/0 - 14

(iii, iv & v)

Note:
1. From 0 and less than 7 is acidic
2. 7 is neutral
3. Greater than 7 to 14 is basic

(i)

Post planting practices on farm to ensure a high yield

1. Supplying/filling in
2. Weed control
3. Thinning
4. Disease control
5. Pest control
6. Earthing-up/stirring the soil
7. Watering
8. Manuring/application of fertilizer
9. Mulching

(ii)

Apparatus needed in the preparation of a standard solution

1. Volumetric flask
2. Beaker
3. Funnel
4. Stirrer
5. Chemical balance
6. Spatula
7. Wash bottle
8. Dropper

(i)

Natural sources of water

1. Rain Water
2. Underground Water
3. Surface Water

(ii)

Water cycle is a set of natural processes that indicate the repeated use and release of water.

OR

Water cycle describes how water evaporates from the surface of the earth into the atmosphere, cools, condenses into rain or snow in the clouds and falls again to the surface of the earth as rain or precipitation.

(iii)

Processes involved in the water cycle

1. Evaporation (from water sources)
2. Transportation (from leaves of plants)
3. Respiration (from humans and animals)
4. Cooling or condensation of vapour (to form clouds or drops of water)
5. Sublimation
6. Falling of rain/precipitation/falling of snow
7. Collection into water sources
8. Used by plants or animals (to start the cycle again)

(iv)

Ways in which water could be contaminated

1. Oil spoilage
2. Domestic waste/sewage discharge into water bodies
3. Discharge of industrial waste into water bodies/waste from mining industries
4. Waste from hospitals
5. e-waste/radioactive waste into underground water
6. Excess inorganic fertilizers washed into water bodies
7. Excess insecticides/herbicides washed into water bodies
8. Petroleum products/gasoline/diesel into water bodies
9. Run-off/silt from construction sites
10. Chemicals/DDT used in fishing
11. Animals stepping into water bodies/drinking
12. Putting dirty hands into water

(i)

Stages of water treatment for public consumption

Screening → aeration → sedimentation → sand filtration → chlorination

(ii)

Significance of the stages in water treatment

(i)

Characteristics of ionic compounds

1. Solid at room temperature
2. Have high melting point
3. Have high boiling point
4. Have high density
5. Generally soluble in polar solvents/water
6. Conduct electricity in molten state/in aqueous solution
7. Exist in crystalline form

(ii)

Why helium does not form a compound

Helium is an element with completely filled valence shell/it is stable/has maximum of 2 electrons in its shell.

It there does not require a transfer or acceptance or sharing of valence electrons for stability.

(i)

Waste management refers to the complete process of collecting, treating and disposing of wastes.

(ii)

Ways by which waste could be managed/useful

1. Through recycling
2. Recovering waste for re-use
3. Turning waste into manure
4. Channeling waste water for agricultural use
5. Treating biomass to become biogas for energy
6. Using husks for making door mats
7. Using water sachets in making bags
8. Using cocoa husks for making soap
9. Generate income

(i)

(ii)

Structural adaptation of mammalian teeth

Incisor has sharp or chisel-shaped edge

Canine has pointed edge or it is conical

Molar has flat or cusped or ridged surface

(iii)

Ways of preventing tooth decay

1. Avoiding eating too much sugary food/sweets
2. Brushing teeth after meals or regularly or twice a day
3. Regular dental check-up
4. Avoid activities leading to aches or bleeding
5. Regular brushing of the tongue
6. Daily flossing
7. Use of antibacterial mouthwash
8. Use of fluoride tooth paste

(i)

Types of chemical bonding

1. Ionic Bonding

Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another. Here, an atom loses an electron, which is, in turn, gained by another atom. When such an electron transfer takes place, one of the atoms develops a negative charge and is now called the anion.

The other atom develops a positive charge and is called the cation. The ionic bond gains strength from the difference in charge between the two atoms, i.e., the greater the charge disparity between the cation and the anion, the stronger the ionic bond.

2. Covalent Bonding

A covalent bond indicates the sharing of electrons between atoms. Compounds that contain carbon (also called organic compounds) commonly exhibit this type of chemical bonding.

3. Metallic Bonding

A metallic bond is a type of chemical bond formed between positively charged atoms in which the free electrons are shared among a lattice of cations. Metallic bonding is the main type of chemical bond that forms between metal atoms.

(ii)

Types of bonding in some chemical compounds

(i)

Copulation is the insertion of the penis into the vagina of a female.

(ii)

Ejaculation is the release/the discharge of semen into the vagina during mating

(iii)

Ovulation is the release of ripe or mature ovum/egg by ovaries

(ii)

Menstruation is the periodic/monthly discharge of blood from the vagina

OR

Menstruation is the regular discharge of blood containing mucosal tissue/dead tissue from the inner lining of the uterus (endometrium) through the vagina.

(i)

Why elements in group I have similar chemical properties

1. Chemical properties are determined by the number of electrons in the outermost shell.

2. Atoms of elements in group I have one electron in their outermost shells

(ii)

Why noble gases are unreactive under normal conditions

Noble gases have full complete electrons in their outmost shells and therefore are very stable.

(i)

Organisms involved in the nitrogen cycle

1. Nitrifying bacteria/nitrobacta/nitrosomonas
2. Nitrogen fixing bacteria/azotobacta/hizobium
3. Denitrifying bacteria
4. Some plants convert nitrate into ammonia

(ii)

(i)

Efficiency of a machine is the ratio of work output to work input expressed as a percentage.

OR

Efficiency = $\frac{\mathrm{Work\; output}}{\mathrm{Work\; input}}$ x 100%

(ii)

Efficiency = $\frac{\mathrm{Energy\; output}}{\mathrm{Energy\; input}}$ x 100%

Energy output = 50 J
Engy input = 80 J

Efficiency = $\frac{\mathrm{50\; J}}{\mathrm{80\; J}}$ x 100% = 62.5% ≈ 63%

(i)

Heat is a form of energy which tells the amount of thermal energy contained in a body

OR

Heat is a form of energy transfer from a high temperature object to a low temperature object

OR

Heat is a form of energy resulting from the motion of atoms and molecules

OR

Heat is a form of energy which raises the temperature of a body

(ii)

Effects of heat on a substance

1. Rise in temperature
2. Change in shape
3. Change in state
4. Change in volume/size

(iii)

Processes by which heat can be transferred

1. Conduction → Solid
2. Convection → Liquid and gas (fluid)
3. Radiation → Vacuum/No material medium

(iv)

Differences between heat and temperature

(i)

Mass number = Number of protons + Number of neutrons

Atomic number = Number of protons

Number of protons = Number of electrons (in neutral atom)

(ii)

Note:
1. Number of electrons = 17
2. First shell takes maximum of 2 electrons
3. Subsequent shells take maximum of 8 electrons
4. Electronic configuration = 2, 8, 7

(i)

Load = 4000 N
Effort = 2000 N

Mechanical advantage (M.A) = $\frac{\mathrm{4000\; N}}{\mathrm{2000\; N}}$ = 2

(ii)

Distance moved by effort = 8 m
Distance moved by load = 4 m

Velocity Ratio (V.R) = $\frac{\mathrm{8\; m}}{\mathrm{4\; m}}$ = 2

(i)

Energy is the ability to do work.

(ii)

(i)

Dispersion of light is the separation of white light into its component colours by refracting medium or prism.

(ii)

(i)

(ii)

Mass = 70 kg
Acceleration due to gravity = 10 ms^-2
Height = 2 m

Potential Energy = 70 kg x 10 ms^-2 x 2 m

Potential Energy = 1400 J

(i)

Wood is a bad conductor of heat therefore cannot conduct heat to the hand when touched making it safe to handle.

(ii)

Railway tracks are made of metals. Metals expand when heated and gaps prevent the crumbling of the tracks/allow for the expansion of the metals.

(i)

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

OR

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

(ii)

Mass = 500.0 g = $\frac{500}{1000}$ = 0.5 kg

Note: the S.I unit of mass is kilogram hence the gram must be converted to kilogram by dividing by 1000

Acceleration due to gravity = 10 m^-2

Distance = 20.0 m

Work done on the stone = 0.5 kg x 20 m x 10 ms^-2

Work done on the stone = 100 J

A stone of mass 500.0 g is raised to height of 20.0 m above the ground.

(i)

Similarities between plant and animal cells

1. Presence of cytoplasm
2. Possession of nucleus
3. Presence of cell membrane
4. Possession of mitochondrion
5. Presence of vacuoles

Differences between plant and animal cells

(ii)