BECE Past Questions & Answers – 2001 (SCIENCE)

SCIENCE Section B

SOLUTIONS

ESSAY

1. (a) (i) Surface tension
Condition existing at the surface of a liquid, resembling a stretched elastic skin
Or:
The property of a liquid that makes its surface behave like a stretched elastic skin

(ii)
House hold devices that use surface tension:
Umbrella, raincoat,tents,etc [any two]

(iii)
Explanation
The cohesive forces that exist among the water molecules results in the water behaving
like a stretched elastic skin over the pores of the household devices, therefore preventing
water from passing through.

(b)
(i)
Constipation
A condition in which a person or animal has difficulty in eliminating solid waste from the
body and the feces are hard and dry

(ii)
Preventing Constipation
 Drinking a lot of water/ liquids
 Eating fruits and vegetables regularly
 Eating foods that contain high amounts of fiber, such as wheat, barley,etc
 Getting enough sleep
 Exercising regularly/ daily
[any four]

(c) Force acting on block
Force = mass × acceleration due gravity
= 10 kg × 10 ms-2
= 100 kgms-2 or 100 N

(d) (i) Colour of litmus paper in sodium hydroxide: blue

(ii) Colour change (to purple)indicates that

the contents of the beaker has changed from a basic nature to a neutral nature
or: that a neutralization reaction has occurred
or: the neutralization process is complete.

(iii) Substance left

(iv) Common salt or

Balanced equation sodium chloride
NaOH+HCl → NaCl +H2O

2. (a) Ways by which plants protect them selves from danger
 Unpleasant smell from certain plants makes them repulsive to animals.
 Unpleasant taste of certain plants makes them undesirable to taste/ eat.
 Sharp thorns / spines of certain plants make them difficult to touch.
 Poisonous parts of certain plants can cause irritation / pain / infection / death.
 Sticky secretions or parts of certain plants makes them uncomfortable to touch
[any three]

(b) (i) Anion: A negatively charged atom
Or: An atom that has gained extra electrons

(ii) NAMES OF PRODUCTS FORMED

α) NH4OHand dilute HCL NH4Cl + H2O
or: ammonium chloride and water

β) CaCO3anddilute HCL CaCl2+CO2+H2O
or: calcium chloride,carbon dioxide and water

(c) (i) Electromagnetism: Magnetism produced by an electric current
or: The process of making a magnet using an electric current

(ii) Circuit diagram

3. (a) (i) Characteristics of roots

 Usually found beneath the ground
 Usually grow downwards
 Grow in the opposite direction to light
 Develop from the embryo’s radicle
 Usually coloured cream or brown
 Root hairs present
[any three]

(ii) Functions of roots
 Absorbs water and mineral salts from the soil
 Holds the plant firmly in place
 Some roots store food prepared by the plant

(b) Conditions necessary for germination of seeds
 viability of seed
 suitable temperature
 water/ moisture
 air

(c) Determination of volume of irregular ball

As shown in the diagram above,
I. Fill a measuring cylinder with water to a suitable volume.
II. Record the volume (V1)
III. Tie a thread / string around the irregular shaped metal ball and gently lower into the water in the cylinder.
IV. Record the new volume (V2)
V. Find difference in volumes (V2– V1)
Volume of metal ball = (V2– V1)

(d) CHEMICAL FORMULA
(i) sodiumchloride NaCl
(ii) (iii) copper sulphate magnesium sulphate CuSO4

MgSO4

(iv) potassium carbonate K2CO3

(e)

(i) (ii) SEPARATING METHOD
iodine and sand Sublimation
ethanol and water Distillation

4.

(a)

(i)

Digestion
The breakdown of food in the body into simpler forms that can be absorbed into the
blood stream and used

(ii)
How food is digested in the stomach
• The digestion of protein begins in the stomach.
• The walls of the stomach secrete a liquid, gastric juice, which contains HCl and
protein digesting enzymes.
• The HCl creates the suitable medium for the enzymes to work properly.
• The protein-digesting enzymes break down proteins into simpler forms.

(b)
(i)
Eclipse of the sun
The situation where the Moon blocks all or part of the Sun’s light from reaching the
Earth’s surface, because it passes directly between the Earth and the Sun
Or:
The case where the moon’s shadow is cast on the earth as it comes between the sun and
the earth.
Or:
When the earth comes between the sun and the moon in a straight line such that the
moon’s shadow is cast on the earth

(ii)
Diagram showing partial and total eclipse

(c) (i) Difference between physical and chemical change
Physical change: No new substance is formed; and the change is reversible
Chemical change: New substance formed;change is irreversible

(ii) Examples of physical and chemical change

Physical change Chemical change
melting of candle cooking of yam
melting of ice rusting of iron
dissolution of salt in water burning of wood into ash
boiling of water action of saliva on cooked starch [anyone]