BECE Past Questions & Answers – 2000 (SCIENCE)

SCIENCE Section B

SOLUTIONS

ESSAY

1. (a) (i) Personal Hygiene
The practice of cleanliness of a person and his/her physical environment

(ii) Ways by which personal hygiene could be maintained
 Bathing regularly(at least twice a day)
 Brushing one’s teeth regularly(advisedly, after each meal)
 Washing one’sclothes regularly
 Washing hands with soap after visiting the toilet
 Keeping one’sroom clean and tidy
 Cleaning one’s bath room and toilet regularly
[any four]

(b) Definition and examples
(i) Compound
a substance formed by the chemical combination of two or more elements in definite proportions
Examples: HCl, orNacl, orCa(OH)2, or CaCl2, or NH3,orMgCO3, etc

(ii) Mixture: A physical combination of two or more substances
Or: a substance consisting of two or more substances that have been combined physically

(c) (i) Machine
A mechanical device that makes work easier and/ or faster

(ii) Examples:
(α) first class lever – Scissors, Crowbar, beam balance, pliers
(β) second class lever – Bottle opener, wheel barrow, paper cutter
(γ) third class lever – human forearm, forceps,base ball bat, broom
[anyone each]

(d) (i) Satellite

Any heavenly body that orbits (revolves around)a larger one

(ii) Use of artificial satellites
 Weather studies and forecasting
 Telecommunication
 Sending and receiving TV signals
 Taking photographs from space for various purposes
 Internet networking
 Global Positioning System (GPS)-a worldwide navigation system
[anyone]

2. (a) Electrostatic force
The force of attraction or repulsion between two stationary electrical charges

(b) (i) Unit of:
(α) force = newton (N)
(β) work = joule (J)

(ii) Work = force × distance
= weight × distance
= (m×g) × distance
= 80 ×10 × 5.0 m
= 4000 joules

(c) Separating mixture of common salt and powdered sulphur
 Add water to the mixture and stir to dissolve the salt
 Pour the mixture through a filter paper in a funnel to separate the powdered sulphur
(residue)from the salt solution (filtrate)
 Heat the salt solution till all the water evaporates,leaving the salt crystals behind
 Dry the powdered sulphur and the salt obtained

(d) Characteristics of
(i) an insect pollinated flower
 Petals are brightly coloured
 Larger size of flowers
 Nectar present
 Attractive scent
 Relatively fewer but larger pollen grains
[any three]

(ii) a wind pollinated flower
 Dull coloured petals
 Nectar absent
 No or unattractive scent
 Relatively more but smaller pollen grains

3. (a) (i) Fertilization: [any three]

The fusion of a male sex cell and a female sex cell to form a zygote
(ii) Processes that lead to fertilization in humans after mating
 During mating, semen is deposited in the vagina and /or womb of the female through the penis of the male.
 The ovary of the female would have already released an egg(ovum) which moves into the fallopian tube.
 Some of the sperms in these men swim into the fallopian tube through the womb.
 One sperm fuses with the released egg to form a zygote in the fallopian tube of the female.

(b) (i) Density
The mass per unit volume of asubstance
Or, mathematically, Density = mass / volume

(ii) Stone’s density
I. Measure the mass(M)of the stone using a beam balance II. Fill a measuring cylinder with water to a suitable volume. III. Record the volume (V1)
IV. Tie a thread / string around the stone and gently lower it into the water in the
cylinder.
V. Record the new volume (V2)
VI. Find difference in volumes (V2– V1)
VII. Volume of metal ball= (V2– V1)
VIII.Find the ratio M/ (V2– V1)= Density of stone

(c) (i) Element
A substance that is made up of the same kind of atoms
Or: Any substance that cannot be broken down into a simpler one by a chemical reaction

(ii) ELEMENT COMPOUND MIXTURE
Potassium Water Air
Alcohol
Common salt
Sugar

4. (a) (i) Alloy
A substance containing two or more metals uniformly physically combined
Or: A homogeneous mixture of two or more metals

(ii) Diffusion
The random movement of atoms, molecules, or ions from one site in a medium to another, resulting in complete mixing

Or:
The movement of particles of a substance from a region of higher concentration to a region of lower concentration
(iii) Colloid
A suspension of tiny particles dispersed in another substance.

(b) Examples of
(i) alloy – bronze, brass, steel,
(ii) colloid- blood, milk, body cream, mayonnaise, emulsion paint

(c) (i) Pollution
Contamination of Earth’s environment with materials that interfere with human health,
the quality of life, or the natural functioning of ecosystems

(ii)

(α)

air: Pollutants
exhaust fumes, smoke, carbon monoxide, sulphur dioxide
(β) (γ) water:
land: Sewage, industrial wastes, crude oil spillage and pesticides chemical fertilizers, fungicides andpesticides

(d)
(i)
Type of energy
= Potential energy

(ii)
Potential energy = weight×height
= 50 N ×15 m
= 750 Nm or 750 J