BECE 2004 Integrated Science Objective Questions and Answers

Solution: Cooling a gas converts it to a liquid (condensation), and further cooling converts the liquid to a solid (freezing). Other sequences violate phase-change principles.

Solution: Friction from rubbing hands generates heat (thermal energy), and the rubbing motion produces audible sound energy. Light/electrical energy isn't typically observed.

Solution: Mercury expands (volume increases) when heated due to thermal expansion, causing the level to rise. Mass/density/weight remain unchanged.

Solution: Conduction transfers heat from the bottom surface to water molecules. Convection circulates heated water (hot water rises, cool water sinks). Radiation is negligible here.

Solution: A dry cell uses chemical reactions (in electrolytes) to generate electrical energy. Bulbs convert electrical→light, loudspeakers/microphones convert electrical↔sound.

Solution:Cells in series are connected end-to-end (typical in X). An open key (switch) breaks the circuit. Parallel cells would show side-by-side connections.

Solution: Diagram Y shows two identical cells in parallel. Parallel cells maintain the voltage of a single cell (1.5V), unlike series which add voltages.

Solution: Longer effort distance (lever arm) provides mechanical advantage, reducing required force (effort) to move the load per the lever principle \(\text{Effort} \times \text{Effort Arm} = \text{Load} \times \text{Load Arm} \).

Solution:Third-class levers have effort applied between fulcrum and load (e.g., tweezers, human arm), sacrificing force for speed.

Solution: A balanced diet requires correct proportions of macronutrients (proteins, carbs, fats/oils), not equal amounts. Water/salt/micronutrients are essential but not defining.

Solution: Benedict’s test detects reducing sugars (e.g., glucose). Brick-red precipitate confirms their presence. Oils/proteins/vitamins don’t produce this result.

Solution: Egg albumen (egg white) is primarily water and proteins (e.g., ovalbumin), with minimal fats/carbs/vitamins.

Solution: All living things grow, respire, and respond to stimuli. "Move about" (locomotion) isn’t universal (e.g., plants, corals).

Solution: After fertilization, ovules mature into seeds. The ovary (not ovules) develops into fruit.

Solution: Onions grow from bulbs (underground storage organs with fleshy leaves). Corms/suckers/rhizomes are used for plants like taro, bananas, or ginger.

Solution: Testes are male reproductive organs producing sperm and testosterone. Blood/lymph/urine are produced elsewhere.

Solution: Pancreas secretes digestive enzymes (e.g., amylase, lipase) into the small intestine. Caecum is vestigial, kidneys filter blood, larynx is for speech.

Solution: HIV/AIDS spreads primarily via sexual contact. Asthma is genetic/environmental, tuberculosis via air, goitre via iodine deficiency.

Solution: Chlorine gas (Cl₂) consists of diatomic molecules, but as a pure substance with one type of atom, it’s an element. Compounds have multiple elements.

Solution: Urine breaks down into ammonia (NH₃), which has a pungent odor. Hydrogen/CO₂/nitrogen are odorless.

Solution: Fe has +2 oxidation state in FeS (since S is -2). Roman numerals indicate metal’s oxidation state: iron(II) sulphide.

Solution: Mercury (Hg) is the only liquid metal at room temperature. Carbon/silver/sulphur are solids.

Solution: "Nimbus" (e.g., nimbostratus, cumulonimbus) denotes rain-producing clouds. Cirrus are wispy, cumulus are fluffy, stratus are layered (non-precipitating).

Solution: Sand has larger particles and more pore spaces, enabling faster drainage. Clay has tiny particles with less space, retaining water.

Solution: Weevils are crop pests (insects) but not parasites—they don’t live on/in hosts. Ticks (ectoparasites), tapeworms/plasmodium (endoparasites) are parasites.

Solution: Houseflies spread cholera by contaminating food with pathogens from feces. Malaria is spread by mosquitoes; measles/tuberculosis by air/human contact.

Solution: Contour ploughing (plowing across slopes) creates ridges that slow water runoff, reducing erosion. Cover cropping/mulching help but are less effective on slopes.

Solution: At night (no photosynthesis), plants respire, consuming O₂ and releasing CO₂. In closed rooms, this could reduce oxygen available for humans.

Solution: Weathering breaks rocks into soil via physical/chemical/biological processes. Erosion transports soil; composting/leaching involve organic matter/nutrient loss.

Solution: Capillary action (movement through narrow tubes via adhesion/cohesion) draws kerosene up the wick. Diffusion/osmosis involve molecules/solvents; suction is pressure-driven.

Solution: Friction opposes relative motion between surfaces. Adhesion/cohesion are attractive forces (different substances/same substance); tension is pulling force.

Solution: Work = Force × Distance → Force = Work/Distance = 720 J / 12 m = 60 N.

Solution: Phloem transports sugars/organic compounds (food) from leaves. Xylem carries water/minerals; cambium produces cells; epidermis is protective.

Solution: Blood carries nutrients (I), O₂ (III), and CO₂ (IV). Urine is transported via the urinary system, not blood.

Solution: Alloys are homogeneous mixtures of metals (e.g., brass). Colloids/aerosols are non-metal mixtures; compounds involve chemical bonding.

Solution: Gold’s low reactivity prevents tarnishing/corrosion, making it ideal for jewelry. Preciousness/expense are secondary; conductivity is irrelevant here.

Solution: Diamond is carbon (non-metal). Mercury/sodium are metals; steel is a metal alloy.

Solution: Alum acts as a coagulant, clumping fine particles (flocculation) for easier sedimentation. Disinfection (germ-killing) uses chlorine/UV.

Solution: Streams collect surface runoff (pollutants, waste). Rainwater is purest; borehole/pipe water undergo filtration/treatment.

Solution: Drying/salting remove water (via dehydration/osmosis), creating a hypertonic environment that inhibits microbial growth by preventing metabolism.