BECE 2002 Integrated Science Objective Questions and Answers

Solution: Carbon dioxide is commonly used in fire extinguishers because it displaces oxygen, smothering the fire and preventing combustion without leaving residue.

Solution: Heating ice first melts it to liquid water (solid→liquid), then boils the water to steam (liquid→vapor), following sequential phase changes.

Solution: \( H_2 \) denotes a diatomic molecule of hydrogen, composed of two chemically bonded hydrogen atoms.

Solution: Physical changes are reversible; sugar dissolved in water can be recovered unchanged via evaporation, confirming no chemical reaction occurred.

Solution: During boiling, absorbed heat energy breaks intermolecular bonds for phase change rather than raising temperature, maintaining a constant temperature.

Solution: Condensation (gas→liquid) reduces particle spacing, decreasing volume while mass remains conserved.

Solution: Stored energy due to the spring's deformed position (mechanical stress) is elastic potential energy.

Solution: At impact, gravitational potential energy is fully converted to kinetic energy due to motion.

Solution: Force fundamentally alters motion (Newton's laws: starting/stopping/changing direction) or deforms objects (e.g., compression).

Solution: Loss in PE = mgh = 50 kg × 10 m/s² × 5 m = 2500 J.

Solution: Plastic lacks free electrons, preventing electrical conduction, unlike metals (copper, zinc) or semi-metals (graphite).

Solution: Gaps accommodate thermal expansion of rails in heat, preventing buckling or deformation.

Solution: Hawks use sharp beaks and talons (claws) for defense and hunting, unlike crabs (pincers), lions (claws), or snakes (fangs).

Solution: Tapeworms reside in host intestines, absorbing nutrients directly, unlike guinea worms (subcutaneous) or plasmodium (blood).

Solution: Boiling kills copepods (water fleas) carrying guinea worm larvae, eliminating the transmission vector.

Solution: Infected female Anopheles mosquitoes inject Plasmodium parasites during blood-feeding.

Solution: Omnivores consume plant- and animal-derived foods, a key dietary classification.

Solution: Autotrophy (e.g., photosynthesis) is exclusive to living organisms; non-living entities cannot produce their own nutrients.

Solution: Plants are primary producers (via photosynthesis), forming the base of food chains; animals lack this capability.

Solution: Toads are ectothermic (cold-blooded), relying on external heat to regulate body temperature, unlike birds (crow) or mammals (rabbit).

Solution: Crop rotation replenishes soil nutrients (e.g., legumes fix nitrogen) and disrupts pest cycles.

Solution: Loam soil (clay+sand+humus) balances drainage (sand), water retention (clay), and nutrients (humus).

Solution: Photosynthesis consumes CO₂ and H₂O to produce glucose and release oxygen as waste.

Solution: The heart pumps oxygenated blood via arteries and receives deoxygenated blood via veins.

Solution: Enzymes (e.g., amylase) break down complex carbohydrates (starch) into simple sugars like glucose.

Solution: The CNS integrates sensory input and coordinates responses via the brain and spinal cord; nerves are peripheral.

Solution: Lungs (CO₂), skin (sweat), and kidneys (urine) eliminate waste; the heart circulates blood but doesn’t excrete.

Solution: Stomata on leaf surfaces facilitate CO₂/O₂ exchange during photosynthesis and respiration.

Solution: Salivary amylase in the mouth initiates starch breakdown into maltose.

Solution: Sperm (haploid gamete) fertilizes the female egg; testis produces sperm but is not the cell itself.

Solution: Okra (Okro) fruits dry and split open violently, ejecting seeds away from the parent plant.

Solution: The ear converts sound waves into nerve impulses via the cochlea for auditory perception.

Solution: Bile (produced by the liver) emulsifies fats in the duodenum, aiding lipid digestion.

Solution: Measles spreads via airborne respiratory droplets from infected individuals.

Solution: Houseflies transmit dysentery-causing pathogens (e.g., Shigella) by contaminating food with feces.

Solution: Mycobacterium tuberculosis primarily infects lung tissue, causing pulmonary TB.

Solution: Constipation results from infrequent bowel movements, leading to hardened stool and straining.

Solution: Solar radiation intensity decreases with distance (inverse-square law), reducing surface temperature.

Solution: Hygrometers measure atmospheric moisture content (relative humidity) using materials sensitive to humidity changes.

Solution: The sidereal month (orbital period relative to distant stars) is approximately 27.3 days.