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2015 WASSCE (November) Integrated Science Paper Two – Essay
1. a) i) What is a living cell?
ii) State four differences between a plant cell and an animal cell.
b) i) What is meat by oxidation number of an atom?
ii) Determine the oxidation number of the atoms underlined in each of the following compounds:
c) i) What is soil erosion?
ii) State one way by which each of the following methods controls soil erosion:
d) i) State two sources of error in scientific experiments.
ii) A student eats a bowl of rice worth 80 J of energy. If the student uses 50 J of the energy in running a 100 m race. Calculate the efficiency of the student’s energy conversion.
a) i) A living cell is the basic or functional unit of life. Or
A living cell is the building block of life.
ii) Differences between plant cell and animal cell
Plant cell Animal cell
Contains chloroplast or manufactures food – Chloroplast is absent or does not manufacture food
Has definite shape – Has no definite shape
Has cellulose cell wall – Has no cell wall
Contains large or permanent vacuoles – Contains small or temporary vacuoles
Stores lipids as oils – Stores lipids as fats
Carbohydrate is stored as starch – Carbohydrate is stored as glycogen
b) i) Oxidation number is a number assigned to an atom in a chemical combination which represents the number of electrons gained or lost.
ii) ?) Let the oxidation number of Mn be x
The oxidation number of O is -2
? ?+ (-2 ? 2) = 0
? – 4 = 0
x = +4
?) Let the oxidation number of Fe be y
2y + (-2 x 3) = 0
2y – 6 = 0
y = +3
?) Let the oxidation number of Cu be z.
2z + (-2 x 1) = 0
2z – 2 = 0
z = +1
c) i) Soil erosion is the removal of top soil by water or wind.
ii) a) Ways by which mulching controls soil erosion
Mulch materials reduce the impact of rain drops that splash soil particles.
Mulching prevents or reduces or controls the speed of run off.
Organic mulch helps bind soil particles tohether
? ) Ways by which ridging controls soil erosion
Ridges help to check the speed of wind or rain water over the surface of the soil
Ridges enhance water infiltration
Ridge prevent run off
d) i) Sources of scientific errors
Defects in measuring instruments
Observation or personal error or parallax
Setting or adjustment of instrument or resolution or failure to calibrate the instrument correctly or zero error
Use of wrong tool or instrument
Inability to control or account for all factors that may affect the experiment
ii) Efficiency = (Energy output)/(Energy input) ? 100
= 50/80 ? 100 = 63%
2. a) State four ecological factors that affect crop production.
b) i) Name two organisms invoved in the nitrogen cycle.
ii) State two processes in the nitrogen cycle that
?) add nitrogen to the soil
?) remove nitrogen from the soil
c) i) State two differences between air mass and storm.
ii) State two effects of air masses on the environment.
d) i) Define the term alloy.
ii) Classify each of the following substances as alloys or isotopes:
a) Ecological factors that affect crop production
• Rainfall or flood
• Pests or diseases
• Sunshine or light
• Other organisms or human actions
• Soil pH
b) i) Organisms involved in the nitrogen cycle
• Nitrifying bacteria or nitrobacta or Nitrosomonas
• Nitrogen fixing bacteria or azotobacta or hizobium
• Denitrifying bacteria
• Some plants convert nitrate into ammonia
ii) ?) Processes that add nitrogen to the soil
• Nitrogen fixation
• Plant growth
• Plant removal or removal of crop
c) i) Differences between air mass and storm
Air mass Storm
Horizontal body of air – Vertical movement of hot air
Moves from a region of high pressure to a region of low pressure – Moves from a low pressure area
Strong wind system – Stronger wind
Covers a large area – Limited to a small area
ii) Effects of air masses on the environment
• Causes acid rain
• Carries harmful radioactive substances from place to place
• Destroys the ozone layer
• Results in global warming
d) i) Alloy is a homogenous or uniform mixture of a metal and other metals or non-metals.
ii) ?) Alloy
3. a) i) List the first three layers of the atmosphere in the correct sequence.
ii) State one difference between the first layer and the third layer in terms of
?) air composition
b) An aqueous solution of 2.0 dm3 contains 53.0 g sodium trioxocarbonate (IV). Calculate the concentration in
i) g dm-3
ii) mol dm-3 [Na2CO3 = 106]
c) i) Explain the term homeostasis.
ii) State three conditions under which homeostasis occurs in humans.
d) i) Give two reasons for controlling weeds among crops.
ii) State two effects of pests on crop production.
a) i) Troposphere, stratosphere and mesosphere
ii) Differences between troposphere and mesosphere
?) Troposphere has plenty air while mesosphere has little air.
? ) Troposphere has high temperature while mesosphere has low temperature.
b) i) Mass concentration = (Mass of solute)/(Volume in dm3)
= (53.0 g)/(2.0 dm3)
= 26.5 g dm-3
ii) Molar concentration
= (Mass Concentration)/(Molar Mass)
= 26.5/106 = 0.25 mol dm-3
c) i) Homeostasis is a process by which living organisms maintains a stable internal environment.
ii) Conditions for homeostasis to occur
When the body temperature rises above or falls below normal.
When the glucose level in the blood is high or low
When the blood pressure or osmotic concentration of the blood falls or rises.
When concentration of mineral salts in the blood rises above or falls below normal.
When the body size changes.
d) i) Reasons for controlling weeds among crops
To prevent weeds from competing with crops for nutrients or water or space or light or air or to prevent overcrowding.
Weeds contaminate harvested crops by reducing their market value.
Weeds promote bush fires
Some weeds are poisonous to both man and livestock.
ii) Effects of pests on crop production
Pests reduce yield of crops considerably
Control of pest can cause total crop lost or death
Damage caused by pests to crops reduce market value of crops
Pets act as vectors
4. a) Distinguish between
i) dilute acid and concentrated acid;
ii) strong acid and weak acid.
b) i) Explain the term tillage as used in crop production.
ii) Give three advantages of tillage.
c) An electric kettle is rated 240 V, 100 W.
i) current that flows through the kettle when in use.
ii) resistance of the element of the kettle.
d) i) What is a pathogen?
ii) State four ways in which the body defends itself against pathogens.
a) i) A dilute acid is one that contains small amount of the dissolved acid or solute in a large volume of solution while a concentrated acid contains large amount of the dissolved acid or molecules in a similar or same volume of solution.
ii) Strong acid is one which dissolves in water and ionizes or dissociates completely while a weak acid is one which dissolves in water and ionizes or dissociates partially.
b) i) Tillage is the cutting or turning or loosening of the soil.
ii) Advantages of tillage
Improves soil acration
Improves water percolation in the soil
Helps to incorporate organic matter into the soil or distribute nutrients throughout the soil.
Helps to incorporate organic matter into the soil or distribute nutrients throughout the soil
Helps easy penetration of roots of crops
Reduces or prevents soil erosion
Controls or destroys pests and diseases
Expose pests for predators
Makes other farm cultural practices easier to undertake
c) i) P = VI
> I = P/V > I = 100/240 = 0.42 A
ii) P = I2R
> R = P/I2
> P = 100/(0.42 ?0.42) = 567 ?
d) i) Pathogen is disease causing agent or microbe or micro-organism.
ii) The body’s ways of defense against pathogens
Blood clots acts as barrier to germs at a cut surface on the body.
Tears kill bacteria
Stomach acid kills bacteria
Phagocytes in the blood engulf or kill bacteria
Lymphocytes produce antibodies which kill bacteria or counter effect of antigene
The skin serves as a barrier to the entry germs.
5. a) i) State two common advantages of crop rotation and land rotation
ii) Give two reasons why planting crops in rows is advantageous.
b) State two general characteristics of each of the following Kingdoms used for classifying organisms:
c) i) What is functional group?
ii) Name the functional group in each of the following compounds:
d) i) Explain briefly how a p-type semiconductor is formed.
ii) Give two uses of radioisotopes.
a) i) Common adavantages of crop rotaion and lnd rotation
• They increase or preserve or improves soil fertility
• They help to break disease or pest cycle
• Fallow periods are included in both systems
• They help to check soil erosion
• They help in saving nitrogenous fertilizers
• They help in weed control
ii) Advantages of planting crops in rows
• Encourages use of farm machines
• Increases plant population per acre
• Easy to replace dead or diseased crops
• Easy to carry out other activities on the farm or it is easy to count plants population in a given farm area or movement in the crop area is more convenient
• Enhances wind or air passage
• Minimizes light exposure
• Enhances visibility
b. i) Characteristics of Fungi
• No roots or stems or leaves
• Consists of hypae or mycelium
• No cellulose cell wall
• Eukaryotic or nucleus with membrane
• Cell wall made of chitin
ii) Characteristics of Protoctista
• No nuclear membrane or prokaryotic
• No membrane-bound organelles
• Flagella may be present
iii) Characteristics of Protoctista
• Consists of collection of similar cells
c) i) Functional group is an atom or agroup of bonded atoms or a bond that determines the chemical properties of organic compunds.
ii) ?) Alkene
?) Alkanoic acid or carbocylic acid
?) Alkanol or alcohol
d) i) Formation of a p-type semiconductor
• A semiconductor material is doped
• Using a trivalent element
• Creating more holes than electrons
ii) Uses of radioisotopes
• In medicine
• In research
• In agriculture
• To treat cancer or diseases
• In tracer techniques or tracing biochemistry process
• To detect welded scams
• To detect leakage or cracks in pipes
• In the manufacture of nuclear weapons
6. a) i) Name two natural resources of hard water
ii) List two chemical substances that are present in permanent hard water.
iii) State one advantage and one disadvantage of hard water.
b) i) What is an electromagnet?
ii) Explain briefly the appearance of a red shirt under green light.
c) i) Define castration as used in animal production.
ii) Give three reasons for castrating animals.
d) i) Explain the term drug addiction.
ii) State two general symptoms of drug addiction.
a) i) Natural sources of hard water
• Sea water
• Lagoon or brackish water
• Well water or borehole
• River water
ii) Chemical substances present in permanent hard water
• Calcium tetraoxosulphate (VI) or CaSO4
• Magnesium tetraoxosulphate (VI) or MgSO4
• Any soluble calcium or magnesium or iron (III) apart from that of bi-carbonates
iii) Advantages of hard water
• Contains essential minerals for bone or teeth formation
• Pleasant to taste
• Does not dissolve metallic or lead pipes
Disadvantages of hard water
• Wastes soap or does not lather easily with soap
• Forms boiler scale thereby wasting energy
• Tends to make white clothes grey
• Interferes with tanning and dyeing of materials
• Forms scum or scales or fur in kettles
b) i) Electromagnet is a magnet made by passing electric current through coils around soft iron material or magnetic material.
ii) The red shirt absorbs all the green light falling on it and reflects none thereby appearing black.
c) i) Castration is the removal of the testes or breaking of the spermatic cord of a male animal so as to render it sexually unproductive.
ii) Reasons for castrating animals
• Remove unpleasant odour
• Prevent in-breeding or indiscriminate crossing
• Make animal docile and easy to handle
• Produce tender meat
• Make animal grow fat
• Prevent spread of diseases through mating
d) i) Drug addiction is the dependence on or intense carving for an illegal drug or medication and from which the person is unable to quit on his/her own.
ii) Symptoms of drug addiction
• Building up drug tolerance
• Taking drugs to avoid or relieve withdrawal symptoms
• Lost of control over one’s drug abuse or wishing to stop but unable to do so
• One’s life revolves around drug abuse
• Abandoning activities or hobbies one use to enjoy
• Perpetual use in spite of the knowledge that it hurts
• Madness or abnormal behavior