2010 WASSCE Integrated Science Paper 2

1. a) i) What is meant by the rate of chemical reaction?

The rate of a chemical reaction refers to the speed at which reactants are converted into products in a chemical reaction. It is usually expressed as the change in concentration of a reactant or product per unit of time, commonly measured in moles per liter per second (mol/L·s).

ii) Explain how each of the following factors affect the rate of a chemical reaction.

α) Concentration:

An increase in the concentration of reactants generally increases the rate of reaction. This is because higher concentration means more reactant particles in the same volume, leading to more frequent collisions between particles, thus increasing the likelihood of successful reactions.

β) Surface Area:

The rate of reaction increases with an increase in surface area. A larger surface area provides more space for reactant particles to collide, resulting in a greater number of collisions and a faster reaction. For example, powdered solids react faster than large chunks.

b) i) Define work.

Work is done when a force acts on an object and causes it to move in the direction of the applied force. Mathematically, work is defined as:
$\text{Work} = \text{Force} \times \text{Distance} \times \cos(\theta)$
Where:

Force is the applied force (in newtons),
Distance is the distance moved by the object (in meters),
θ is the angle between the force and the direction of motion.

ii) A stone of mass 500.0g is raised to a height of 20.0 m above the ground. If the acceleration due to gravity is 10.0 m/s², calculate the work done on the stone.

The work done in lifting the stone can be calculated using the formula:
$\text{Work} = \text{Force} \times \text{Distance}$

First, calculate the force (weight of the stone):
$\text{Force} = \text{mass} \times \text{gravity} = 0.5 \, \text{kg} \times 10.0 \, \text{m/s}^2 = 5.0 \, \text{N}$

Now, calculate the work:
$\text{Work} = 5.0 \, \text{N} \times 20.0 \, \text{m} = 100 \, \text{J}$
So, the work done is 100 joules (J).

c) Describe the mechanism of inhalation in humans.

Inhalation is the process of breathing in air into the lungs. It involves:

Diaphragm contraction: The diaphragm contracts and moves downward, increasing the volume of the thoracic cavity.
Intercostal muscles: The external intercostal muscles contract, raising the ribs and expanding the chest cavity.
Lower pressure in lungs: As the volume of the thoracic cavity increases, the air pressure in the lungs becomes lower than the atmospheric pressure, causing air to flow into the lungs through the trachea.

d) State one use each of the following equipment used in crop production:

i) Garden fork: Used for loosening, turning, and aerating soil to improve its texture for planting.
ii) Hand trowel: Used for digging small holes, planting seedlings, and transplanting plants.
iii) Secateurs: Used for pruning or cutting small branches and stems of plants.
iv) Shares: Used in plowing to break up and turn over the soil during land preparation.
v) Mattock: Used for digging, breaking up hard soil, or weeding in tough ground.

2. a) Explain why:

i) Wood is used as a handle for some cooking utensils.

Wood is used because it is a poor conductor of heat, meaning it doesn't become hot quickly, preventing burns when cooking. Additionally, wood is strong, lightweight, and durable.

ii) Gaps are left in railway tracks.

Gaps are left in railway tracks to accommodate thermal expansion. As metal rails expand in hot weather, the gaps prevent them from bending or warping, ensuring the track remains stable.

b) Classify the following groups of crops as vegetables, cereals, grain legumes, and root tubers:

i) Cassava and sweet potatoes – Root tubers
ii) Cowpea and groundnut – Grain legumes
iii) Maize and millet – Cereals
iv) Pepper and tomatoes – Vegetables

c) i) What is immunity?

Immunity is the body's ability to resist harmful microorganisms, such as bacteria, viruses, and toxins, through the action of the immune system.

ii) State three ways by which humans acquire immunity.

Innate immunity: Inherited immunity, present from birth, provides general protection against pathogens.
Acquired immunity: Gained through exposure to infections or vaccinations, which stimulate the immune system to produce antibodies.
Passive immunity: Acquired through the transfer of antibodies, such as from mother to child through breast milk.

d) List two examples of processing devices of a computer.

Central Processing Unit (CPU): The brain of the computer that processes data and instructions.
Graphics Processing Unit (GPU): A specialized processor for handling visual rendering and graphical tasks.

e) A piece of zinc metal was placed in a beaker containing dilute hydrochloric acid.

i) Write a balanced chemical equation for the reaction.

The reaction between zinc and hydrochloric acid produces zinc chloride and hydrogen gas:

\text{Zn} (s) + 2\text{HCl} (aq) \rightarrow \text{ZnCl}_2 (aq) + \text{H}_2 (g)

ii) If 5.0 g of zinc was placed in the acid, how many moles of hydrochloric acid would be required to react with the zinc?

First, calculate the moles of zinc:

\text{Moles of Zn} = \frac{\text{Mass of Zn}}{\text{Molar mass of Zn}} = \frac{5.0 \, \text{g}}{65.4 \, \text{g/mol}} = 0.0765 \, \text{mol}

The balanced equation shows that 1 mole of Zn reacts with 2 moles of HCl. Therefore, the moles of HCl required:

\text{Moles of HCl} = 2 \times 0.0765 \, \text{mol} = 0.153 \, \text{mol}

So, 0.153 moles of hydrochloric acid are required.

3. a) i) Explain the term parturition as applied to animal production.

Parturition refers to the process of giving birth in animals. It involves the delivery of offspring from the reproductive system of a female animal.

ii) State three signs shown by an animal when parturition is about to occur.

Restlessness: The animal becomes anxious and may move around frequently.
Increased nesting behavior: The animal may prepare a nest or seek a quiet, comfortable place.
Physical changes: The animal may show signs like enlarged or engorged mammary glands, mucus discharge from the vagina, or visible contractions.

b) i) What is plant tissue culture?

Plant tissue culture is a technique used to grow plant cells, tissues, or organs in a sterile environment on a nutrient medium under controlled conditions. This technique is used for plant propagation, breeding, and research.

ii) State three advantages of propagating a plant by tissue culture.

Rapid production: It allows for mass production of identical plants in a short period.
Disease-free plants: Tissue culture can produce plants free from diseases and pests.
Genetic uniformity: The plants produced are genetically identical to the parent plant.

c) The atomic number of atom X is 17 and its mass number is 35.

i) Indicate the number of protons, electrons, and neutrons in the atom.

Protons = Atomic number = 17
Electrons = In a neutral atom, electrons = protons = 17
Neutrons = Mass number - Atomic number = 35 - 17 = 18

So, atom X has:

17 protons
17 electrons
18 neutrons

ii) Draw the electron configuration of the atom showing positions of the protons and the arrangement of the electrons in the various shells.

Electron configuration: $2, 8, 7$

2 electrons in the first shell
8 electrons in the second shell
7 electrons in the third shell

d) i) What is the centre of gravity of a body?

The center of gravity of a body is the point at which the entire weight of the body can be considered to act. It is the average position of the mass of the object.

ii) Explain why it is more suitable to locate the load compartment of a bus under the passenger seats than at the top of the bus.

Placing the load compartment under the passenger seats lowers the center of gravity of the bus, making it more stable. A lower center of gravity reduces the risk of the bus tipping over, especially when

turning or driving on uneven roads.

4. a) Describe how pollination takes place in an insect-pollinated flower.

Insect-pollinated flowers attract insects (like bees) with their color, scent, and nectar. As the insect moves from one flower to another, it brushes against the anthers, picking up pollen. When the insect visits another flower, the pollen is transferred to the stigma, facilitating fertilization.

4. a) i) Explain the following statement: Though glucose is the substance formed during photosynthesis in leaves, it is starch which is tested for to show that photosynthesis has taken place.

During photosynthesis, glucose is produced in the chloroplasts, but it is quickly converted into starch for storage in plant cells. Starch is more easily tested because it does not dissolve in water and can be detected using iodine solution, which turns blue-black in the presence of starch.

b) State three uses of computers in medicine and health care delivery.

Medical records management: Computers are used to store and manage patient records digitally, improving accessibility and organization.
Diagnosis and imaging: Computers are used in diagnostic tools like CT scans, MRIs, and X-ray machines to analyze medical images.
Telemedicine: Computers facilitate remote consultations between patients and healthcare providers via video conferencing.

c) Consider the following organic compounds:

C3H6, C3H5OH, CH3COOH, and CH3COOCH3

i) Which compound will undergo polymerization?

C3H6 (Propene) is an alkene and can undergo polymerization to form polypropylene.

ii) Which compound will give a pleasant smell?

CH3COOCH3 (Methyl acetate) is an ester and has a pleasant fruity smell.

iii) Which compound will liberate carbon dioxide with sodium hydrogen trioxocarbonate (IV)?

CH3COOH (Acetic acid) will react with sodium bicarbonate (sodium hydrogen trioxocarbonate (IV)) to release carbon dioxide:

\text{CH}_3\text{COOH} + \text{NaHCO}_3 \rightarrow \text{CH}_3\text{COONa} + \text{H}_2\text{O} + \text{CO}_2

iv) Which compound will decolorize bromine water?

C3H6 (Propene), an alkene, will decolorize bromine water because alkenes undergo addition reactions with bromine.

d) Draw and label a ray diagram to show how the image of a point object is seen in a plane mirror.

A simple ray diagram shows a point object placed in front of a plane mirror. A ray of light from the object strikes the mirror, reflects off the mirror, and forms an image behind the mirror. The image is virtual, upright, and laterally inverted.

e) State three measures of reducing incidence of diseases in a fishpond.

Maintaining clean water: Regularly changing and filtering the water to remove waste and toxins.
Proper stocking density: Avoid overcrowding to prevent stress and the spread of diseases.
Using disease-resistant fish strains: Stock fish breeds that are more resistant to common diseases in fishponds.

5. a) i) What is a computer hard disc?

A computer hard disk is a storage device used to store data in a magnetic form. It provides long-term storage for operating systems, software, and files.

ii) State two advantages of hard disc:

High storage capacity: Hard disks can store large amounts of data.
Fast data retrieval: Hard disks provide fast access to stored data compared to some other storage devices.

b) State four benefits of nuclear energy to humans.

Low greenhouse gas emissions: Nuclear power produces little to no carbon dioxide compared to fossil fuels.
High energy output: A small amount of nuclear fuel can produce a large amount of energy.
Reliable energy source: Nuclear energy provides consistent, base-load power generation.
Reduces dependence on fossil fuels: It helps diversify energy sources, reducing reliance on oil and coal.

c) i) What is weathering of rocks?

Weathering is the breakdown of rocks into smaller particles through physical, chemical, or biological processes. It prepares rocks for erosion.

ii) State two effects of temperature on weathering of rocks.

Thermal expansion: Rocks expand when heated and contract when cooled, which can cause cracking.
Freeze-thaw: Water trapped in rock cracks freezes and expands in cold weather, breaking rocks apart.

d) Describe an improvement practice that could be adopted for vegetable crop production in the following soil conditions:

i) Acidic soil:

Lime application: Add agricultural lime to raise the pH and neutralize acidity.

ii) Saline soil:

Leaching: Apply excess water to flush out salts and reduce salinity.

e) i) List two kingdoms used in the classification of living things.

Animalia (Animals)
Plantae (Plants)

ii) State two reasons for classification of living things.

To organize organisms: Classification helps in organizing and grouping organisms based on shared characteristics.
To understand relationships: It helps scientists understand the evolutionary relationships between organisms.

6. a) i) What is friction?

Friction is the resistive force that opposes the relative motion or attempted motion between two surfaces in contact. It acts in the opposite direction of movement and can either slow down or prevent motion.

6. a) ii) State two disadvantages of friction.

Causes wear and tear: Friction between moving parts can lead to damage or degradation over time.
Reduces efficiency: It causes energy losses in the form of heat, making machines less efficient.

6. b) The diagram below is an experimental setup used to separate a mixture of ink and water. Study it and answer the questions that follow.

(Note: Since the diagram is not shown here, we will assume it's a basic distillation or evaporation setup based on the context.)

i) Identify the method of separation used in the setup.

Distillation (if the ink is a solution and you want to recover water), or Evaporation (if you only want the ink residue).

ii) Label the parts of the setup.

(Assuming a simple distillation setup, typical labeled parts might include):

A – Heat source (e.g., Bunsen burner)
B – Distillation flask containing ink and water
C – Condenser (cooling the vapor to liquid)
D – Receiver or collecting flask (where water distillate is collected)

iii) What is the physical property of the components of the mixture that makes the separation possible?

The difference in boiling points — water boils and evaporates at a lower temperature than ink pigments, allowing separation by distillation or evaporation.

6. c) i) What is a cell in living organisms?

A cell is the basic structural, functional, and biological unit of all living organisms. It is the smallest unit capable of carrying out the processes of life.

6. c) ii) State three differences between plant and animal cells.

Plant Cell	Animal Cell
Has a cell wall	No cell wall
Contains chloroplasts	No chloroplasts
Has a large central vacuole	Has small or no vacuole
Generally rectangular in shape	Generally round or irregular

6. d) State four methods of maintaining good sanitation at home.

Proper waste disposal: Regularly dispose of garbage in covered bins.
Clean water supply: Use safe, treated water for drinking and cooking.
Regular cleaning: Sweep, mop, and disinfect floors and surfaces.
Toilet hygiene: Keep toilets clean and ensure proper sewage systems are in place.

6. e) i) State three reasons why it is advisable to eat a balanced diet.

Provides energy for daily activities.
Supports growth and repair of body tissues.
Boosts the immune system, helping to prevent diseases.

6. e) ii) List four classes of food that make up a balanced diet.

Carbohydrates
Proteins
Fats and oils
Vitamins and minerals (can be separated into two classes)
Water