Bece Past Questions & Answers – 2015 (Science)

 

JUNE 2015     (SECOND SITTING)

INTEGRATED SCIENCE 2

ESSAY

SOLUTIONS

 

PART I

[40 marks]

 

1. (a)

• Name the disease illustrated on the pod [1 mark]

Black pod disease

 

• Mention the causative organism of the disease [1 mark]

Fungus (Phytophthora spp.pathogens)

 

• Describe one symptom of the disease [2 mark]

Little yellow spots, which turn brown and enlarge to a dark brown or black lesion within a few days

 

• State one farm practice that promotes the spread of the disease [1 mark]
• Late harvesting of ripe pods
• Insufficient spacing of tree
• Allowing infected pods to remain on trees for a long time

 

• Give two practices farmers could adopt to control the disease [2 mark]

Cultural control practices

• Removal of infected pods
• Wider spacing of trees
• Pruning of trees
• More frequent ripe pod harvesting

 

Chemical control practice

Application of fungicide

 

 

(b)

• Measure and record the length of each of the sides labelled a, b and c, in centimetres.

[3 marks]

Length of side a      =          2 cm

Length of side b      =          4 cm

Length of side c      =          5 cm

 

• Determine the area of each of the faces A and B             [4 marks]

Area of face A        =          Side a  ×  Side b

=          2 cm × 4 cm

=          8 cm²

 

Area of face B        =          Side b  ×  Side c

=          4 cm  ×  5 cm

=          20 cm²

 

• If the weight of the cuboid is 100 N, determine the pressure exerted by the cuboid in N/cm² when it lies on

(α)      face A

Pressure on A   =            =         

=            =          12.5 N/cm²

 

(β)      face B.

Pressure on B  =                     =          5 N/cm²                       [4 marks]

 

• From your results in (iii), explain how pressure exerted by a body changes with the area on which it lies             [2 marks]

 

• From the results in (iii) above, it is clear that pressure increases with decreasing area over which it is exerted, given that the force applied is constant.
• In other words, given a constant force, the greater the surface area over which the force is applied, the lesser the pressure; and the lesser the surface area, the greater the pressure.
• In other words, where force is constant, pressure is inversely proportional to the surface area over which it is applied.

 

(c)     The diagrams below are illustrations of three different types of teeth, labelled A, B and C, in humans

          Study the diagram carefully and answer the questions that follow

• Name each type of teeth labelled A, B and C. [3 marks]

A     –           molar

B     –           canine

C     –           premolar

 

• State one function of each type of teeth labelled A, B and C. [3 marks]

A     –           crushing or chewing or grinding food

B     –           holding/griping or tearing food

C     –           holding/griping or crushing food

 

 

• State two observable differences between the tooth labelled A and that labelled B

                                                                                                                             [2 marks]

Tooth A                                          Tooth B

3 pointed projections (cusps)          Only 1 pointed projection (cusp)

Broad or wide                                 Narrow

 

• Mention two ways of ensuring proper dental care. [2 marks]
• Brushing teeth after meals at least twice a day
• Avoid taking very hot or very cold foods or drinks
• Avoid taking lots of sweets, especially ones that stick to the teeth
• Avoid picking teeth with very sharp/ hard objects
• Regularly eat foods rich in calcium, phosphorus and vitamins
• Visit the dentist regularly for check ups

 

 

(d)

• Name each of the parts labelled I, II, III and IV. [4 marks]

1. –         Retort stand
2. –      Thermometer

• –   Condenser

1. –   pure water (distillate)

 

• Name the method of separation used. [1 marks]

Distillation

 

• State one function of each of the parts labelled II and III [2 marks]

II     –           Measures the temperature within the flask

III   –           It cools the steam (water vapour) or condenses the steam

 

 

• Name three physical processes that are involved in the separation of the mixture.

Evaporation/ vapourisation, condensation, crystallisation [3 marks]

 

 

PART II

[60 marks]

Answer four questions only from this section

 

2. (a)    (i)      What is technology?

The use of scientific knowledge to solve problems in everyday life

Or

The application of scientific knowledge and methods to make life / work easier, faster and more comfortable

Or

The study, development, and application of devices, machines, and techniques for manufacturing and productive processes

 

(ii)     State two differences between science and technology.                             [4 marks]

 

SCIENCE	TECHNOLOGY
Aims at gaining knowledge about nature	Aims at applying scientific knowledge to solve problems
Focuses more on experimentation and analysis	Focuses more on synthesis of design
Mainly theory based	Mainly practical based
Generally cannot be used to solve everyday problems	Are generally used to solve everyday problems

 

 

(b)     Draw potassium atom and show the distribution of electrons in its shells. [K = 19]                                                                                                               [4 marks]

(c)     What energy transformations take place in each of the following activities?

(i)    Using a flashlight battery to produce light in a bulb.

Chemical energy → Electrical energy → Light energy and heat

 

(ii)   Using a microphone to address a gathering.                                     [4 marks]

Electrical energy→ Sound energy

 

(d)     List three components of soil.                                                                             [3 marks]

• Mineral matter / rock particles,
• organic matter/humus,
• water,
• air,
• micro-organisms

 

3. (a)    (i)    Mention the junctions of a transistor.

p-n junction

n-p junction

 

(ii)     Draw the circuit symbol for n-p-n transistor                                              [4 marks]

(b)     State one function of each of the following parts of the human circulatory system:

(i)      blood

• Transports oxygen to the cells of the body
• Transports metabolic waste materials away from the cells of the body
• Transports digested food nutrients to parts of the body
• Helps to maintain a uniform body temperature
• Prevents excessive blood loss by clotting.
• Helps to protect the body against infections and diseases

 

(ii)     blood vessel

• Carries blood from the heart to/from the parts of the body
• Helps in controlling the blood pressure within the body

 

(iii)    heart                                                                                                            [3 marks]

Pumps blood to the parts of the body

 

(c)     Classify each of the following substances as element, compound or mixture:

• air –           mixture
• brass –           mixture
• chlorine –           element
• gold – element
• water –           compound                                                                   [5 marks]

 

(d)     State three ways of caring for farm machines                                                     [3 marks]

• Oiling or greasing metal parts
• Washing and drying after use
• Tightening bolts and nuts when loose
• Sharpening cutting edges when blunt
• Using them for their intended purposes only

 

 

4. (a) (i)    State two physical properties of water

• Colourless,
• odourless
• tasteless
• freezes at 0° Celsius
• boils at 100° Celsius
• density of 1 g/cm3 (at 4°C)
• Among liquids, is a good conductor of heat
• Universal solvent
• High surface tension

 

(ii)     Using litmus paper, explain why water is neutral.                         [3 marks]

Blue litmus paper turns red in acidic medium and red litmus paper turns blue in basic medium. The colour of litmus paper, whether red or blue, remains the same in the presence of water. This shows that water is neutral, meaning it is neither acidic nor basic. (Pure water has a pH of 7)

 

 

(b)     Give one function of each of the following nutrients in plants

(i)      nitrogen

• Essential for photosynthesis (carbohydrate production), due to its presence in chlorophyll
• Promotes rapid growth of plants, as a component of plant protein.

 

(ii)     potassium                                                                                                    [2 marks]

• Regulates the opening & closing of stomata
• Enables the plants to withstand extreme temperatures
• It increases the plants’ ability to use water more efficiently
• Facilitates the production of starch from sugars
• Essential for the synthesis of protein

 

(c)     (i)      State two human activities that disrupt the carbon cycle.

• Destruction of forests and other vegetative cover
• excessive release of carbon dioxide and other gaseous carbon compounds from industries, vehicles, etc into the atmosphere.
• bush burning
• global warming

 

(ii)     State two effects of the disruption of the carbon cycle on the environment. [4 marks]

• depletion of the ozone layer
• global warming due to the greenhouse effect
• extinction of certain species of animals

 

(d)     (i)      What is density of a body?

• The mass per unit volume of the body

Or

• Density =          mass of a body/volume of a body

 

 

(ii)     A body of mass 50 kg has a density of 2 kg/m³. Calculate the volume of the body. [5 marks]

Volume = Mass/Density

= 50kg/2kg/m³

=25 m³

 

5. (a)    What is a vegetable crop?                                                                                    [2 marks]

A plant that is grown for food, whose edible parts can be eaten either raw or semi-cooked

 

(b)     (i)      What is air pollution?

 

Contamination of Earth’s atmosphere with materials that interfere with human health, the quality of life, or the natural functioning of ecosystems

OR

Introduction into the air of a substance which has harmful or poisonous effects on living things and the earth

 

(ii)     State two human activities that lead to air pollution.                                 [4 marks]

• burning of bush, tyres, etc
• mining
• Driving vehicles that release lots of exhaust fumes
• Construction
• Burning of coal and petroleum in industries

 

(c)     (i)      List three modes of heat transfer

• Conduction
• Convection
• Radiation

 

(ii)     Name the type of medium in which each mode of heat transfer you have listed in (i) takes place                                                                                                            [6 marks]

• Conduction –           solid,
• Convection –           liquid, gas
• Radiation –           vacuum

 

(d)     Give three reasons why proteins are important in the diet of mammals.            [3 marks]

• Builds the body cells / tissues
• Repairs worn out / damaged body cells/tissues
• Help speed up certain chemical reactions in the body
• Help provide energy to the body if carbohydrates and fats are insufficient.

 

6. (a)    State one function of each of the following parts of the human reproductive system

• penis
• Passes semen into the vagina of a woman during sexual intercourse
• Passes urine out of the man’s body

 

• ovary
• Produces ova /eggs (female sex cells)
• Produces reproductive hormones, oestrogen and progesterone

 

• oviduct
• place where fertilization takes place
• Carries the egg from the ovary to the uterus or womb

 

• testis
• Produces sperm / spermatozoa (male sex cells)
• Produces the hormone testosterone

 

• uterus [5 marks]
• place where implantation takes place
• Receives and shelters the embryo during pregnancy

 

(b)     (i)      What is electrical conductor?

Any material that allows electricity to flow through easily

 

(ii)     List two substances which are insulators.                                                  [4 marks]

Plastic, polythene, wood, rubber, paper, fabric, glass, gum

 

(c)     State three ways of maintaining soil fertility.                                                     [3 marks]

• Crop rotation
• composting
• mulching
• Fertilizer application
• Bush fallowing
• Green manuring
• Planting of cover crops
• Mixed farming
• crop rotation
• introduction of earthworms and other soil organisms

 

(d)     Write a word equation for each of the following chemical reactions:

• oxygen and hydrogen

oxygen + hydrogen →         water

or

oxygen + hydrogen →         hydrogen peroxide

 

• nitrogen and hydrogen

nitrogen + hydrogen           →         ammonia

 

• sodium and chlorine

sodium and chlorine →       sodium chloride (common salt)                                                                                                                                                                  [3 marks]

 

END OF PAPER