BECE Past Questions & Answers – 1993 (SCIENCE)

SCIENCESectionB

SOLUTIONS

ESSAY

1. (a) (i) Element
A substancethat is madeup ofthe same kind of atoms
Or:
Anysubstancethat cannot be broken down into asimpleronebya chemical reaction

(ii)
Mixture
A physical combination of two ormoresubstances
Or:
A substance consistingof two or moresubstancesthat havebeen combinedphysically

(iii)
Compound
A substance formed bythe chemical combination of elements in fixed proportions
Or:
A substance containingtwo ormore elements that are chemicallycombined

(b) Explanation
(i) Work
Work is donewhen an applied forcemoves an object in the direction oftheforce.
Or:
Thetransfer ofenergy, measuredas the product ofthe force applied to a bodyand the distancemoved bythat bodyin thedirection ofthe force
Or:
Work = f × d, where f = forceapplied
and d = distance moved in the directionoftheappliedforce

(ii) Energy
The ability/ capacitytodo work

(c) UNIT
(i) (ii) (iii) (iv) Power
Energy
Electriccurrent
Temperature – watt(W)
– joule (J)
– ampere(A)
-Kelvin (K) or degreeCelsius (°C) ordegreeFahrenheit(°F)

(d) Potential Energy = mass ×height × acceleration due to gravity
= 100 kg×2 m×10 ms–2
= 2000kgm2s–2 or 2000 N

(e) Characteristics
(i) An insect pollinatedflower
 Petals arebrightlycoloured
 Larger sizeofflowers
 Nectarpresent
 Attractivescent
 Relativelyfewer but larger pollengrains
[anythree]

(ii) a wind pollinatedflower
 Dull coloured petals
 Nectarabsent
 No orunattractivescent
 Relativelymorebut smallerpollen grains
[anythree]

2. (a) (i) Balanced diet
A diet that contains all the essential food nutrientsin their right proportions

(ii)
Classes of food
Carbohydrates, proteins, fats and oils, vitaminsand minerals

(iii)
Function(s)ofeachclass

FoodClass Function(s)

Carbohydrates  Provide energyto thebody
 Glucose helps thebrain cells to function properly
 Glucose help maintain tissueprotein
 Glucose help metabolizefats
 Glucose fuels thecentralnervous system

Proteins  Build the bodycells / tissues
 Repair worn out /damaged bodycells/tissues
 Help speed upcertainchemical reactions in the body
 Help provide energyto thebodyif carbohydrates and fats areinsufficient

Fats and oils  Protect the bodyfrom extreme cold or heat
 Serveas a storeofenergyfor thebody
 Help in buildingthe membranes that surround the bodycells

 Help thebodyto absorbcertain vitamins

Vitamins  Strengthens the body’s immune system
 Helps thebodyto fightagainstdiseases
 Facilitates themetabolicactivities in thebody

Minerals  Ensurehealthygrowth ofteeth and bones
 Help with enzymeaction
 Help with muscle contraction
 Help with nerve reaction
 Help with blood clotting

(b) Diagramto showpinhole camera image

(c) Laws ofreflection oflight
 The angle ofincidenceis equal to the angle ofreflection

 Theincident ray, the reflected rayand the normal,at thepointof incidence,alllie in thesameplane

(d) (i) Howions areformed fromatoms
Atoms become chargedwhen theylose orgain electrons in order to bemorestable or attain a completelyfilledoutershell. When atoms gainelectrons, theybecome negatively charged ions, knownas anions; when theyloseelectrons, theybecomepositivelycharged ions, known as cations

(ii)

PROTON ELECTRON
positivelycharged negativelycharged

located in the nucleus ofan atom located outsidethe nucleus, on the
shells of an atom
relativelyheavy relativelyverylight

3. (a) (i) Electromagnetism
Magnetism produced byan electric current
or:
Theprocess of makingamagnet usinganelectriccurrent

(ii)
Diagramshowing hownailcan bemagnetized

(b) Symptoms ofmalaria
 fever
 bodypains
 feelingcold or hot
 headache
 nausea
 lack of appetite [anythree]

(c) Ways ofkeeping the environmentclean
 Clearing chokedgutters
 Clearing weedyareas
 Buryingemptycans
 Covering rubbish bins
 Sweepingdirtyareas
 Scrubbingtoilets and bathrooms

(D) NewSubstanceFormed
(i) Ammonia (NH3) and dilutehydrochloricacid(HCl);
NEW SUBSTANCE: Ammonium chloride (NH4Cl)

(ii) Sodiumhydroxide (NaOH) and dilute hydrochloric acid (HCl);
NEW SUBSTANCE: Sodiumchloride (NaCl)and water(H2O)

(iii)
Calcium carbonate (CaCO3) and dilute hydrochloric acid (HCl).
NEW SUBSTANCE:Calcium chloride (CaCl2), Carbondioxide (CO2) and water(H2O)

4.
(a)
(i)
Satellite
A satellite is anyheavenlybodythat orbits (revolves around)alarger one.

(ii)

Natural Satellite Artificial Satellite
Created byGod(ornature) Manufactured byman
Has no mechanical orelectrical
devices Has man-mademechanical or
electrical devices
[anyone]

(iii) Uses ofartificial satellites
 Weatherstudies and forecasting
 Telecommunication
 SendingandreceivingTV signals
 Takingphotographs fromspace for various purposes
 Internet networking
 Global PositioningSystem (GPS)-aworldwide navigation system
[anytwo]

(b)

MASS WEIGHT
the amountof matter asubstance
contains the force exerted on abodyasa
resultofgravity
remains constant (unchanging)
regardless of location varies with location
(dependingongravitational force acting at that point)
Units =kilogram (kg) Units =newton (N)

(c) CHEMICAL FORMULA
(i) Calciumoxide; CaO
(ii) (iii) Water;
Coppersulphate H2O CuSO4

(d) EFFECT ON BLUE LITMUS PAPER(i) Sodiumhydroxidesolution;- Remains blue

(iii) Breadat theduodenum
Enzymes in thepancreaticjuice, from the pancreas, break down thebread(sugars and starches) into simple sugars.