BGCSE Science Double Award Paper 1 2017 Exhaustive Study Guide

Examination Overview and Instructions

• Subject: Science: Double Award     * Level: Botswana General Certificate of Secondary Education (BGCSE)     * Paper Code: 0569/01 (Multiple Choice)     * Date: October/November 2017     * Duration: 1 hour 30 minutes     * Total Questions: 60 marks (1 mark per correct answer; no deduction for wrong answers).     * Additional Materials Provided: Multiple Choice Answer Sheet, Soft Pencil (B or HB), and a Periodic Table (printed on page 24 of the booklet).     * Prohibited Materials: Staples, paper clips, highlighters, glue, or correction fluid.

Physics: Mechanics and Motion

• Instrument Accuracy: The accuracy of a measuring instrument is determined by the smallest division on its scale. For length measurement, an instrument with finer gradations (such as a micrometer or specialized scale) provides the most accurate reading compared to standard centimeters.
• Free Fall and Terminal Velocity:     * When an object falls freely through the air, it accelerates due to gravity ($g$) until the upward force of air resistance (drag) equals the downward force of weight.     * At this equilibrium, the object reaches terminal velocity, characterized by a constant speed where acceleration is $0$.     * On a velocity-time ($v-t$) graph, this appears as a curve that levels off into a horizontal line.
• Calculating Maximum Height:     * For an object projected vertically with initial velocity ($u$), final velocity at maximum height ($v$) is $0\,m/s$.     * Given $u = 10\,m/s$ and $g = 10\,m/s^2$, using the equation $v^2 = u^2 - 2gs$:     * $0 = (10)^2 - 2(10)(s)$     * $100 = 20s$     * $s = 5.0\,m$
• Work Done on an Inclined Plane:     * Work done ($W$) is calculated as the product of the force applied ($F$) and the distance moved in the direction of the force ($d$).     * $W = F \times d$     * If a force of $250\,N$ pulls a box along a $10\,m$ incline, the work done is: $250\,N \times 10\,m = 2500\,J$.

Physics: Thermal Physics and Waves

• Thermometry: A liquid-in-glass thermometer operates on the principle of thermal expansion, specifically the expansion of the liquid (mercury or alcohol) relative to the glass capillary tube.
• Heat and Expansion: When a flask of liquid is heated, the liquid level in the capillary tube may drop slightly before rising. This occurs because the flask (solid container) expands first upon contact with heat, increasing the internal volume before the heat reaches the liquid to cause its expansion.
• States of Matter and Cooling Curves:     * Substances undergoing cooling will show a drop in temperature over time.     * A constant temperature plateau (e.g., staying at $40.0 \, ^\circ C$ for several minutes) indicates a change of state where latent heat is being released.     * Example: If substance P stops dropping in temperature at $40.0 \, ^\circ C$, it has likely reached its freezing point and is transitioning from liquid to solid.
• Wave Frequency:     * Frequency ($f$) is the number of waves per second, calculated as $f = \frac{1}{T}$, where $T$ is the period (time for one complete oscillation).     * On a displacement-time graph, if one wave occurs every $2\,s$, the frequency is $0.50\,Hz$.
• Sound Waves:     * Sound requires a medium to travel. In a vacuum (created by removing air from a bell jar), the sound will fade away, even though the mechanical vibration of the bell hammer remains constant.     * Echo Distance: The distance ($d$) to a reflecting surface is calculated using $2d = v \times t$ (since the sound travels to the cliff and back).     * Given speed ($v$) = $320\,m/s$ and time ($t$) = $0.6\,s$: $d = \frac{320 \times 0.6}{2} = 96\,m$.

Physics: Electricity and Magnetism

• Units of Measurement:     * Charge ($Q$): Coulomb (C)     * Current ($I$): Ampere (A)     * Potential Difference/Voltage ($V$): Volt (V)     * Power ($P$): Watt (W)
• Circuit Laws:     * In a parallel circuit, the total current entering a junction must equal the sum of the currents leaving (Kirchhoff's First Law).     * Ohmic Conductors: For a material following Ohm's Law, the current-voltage ($I-V$) graph is a straight line passing through the origin, indicating that $I \propto V$.
• Electrical Power:     * Power for a single component: $P = V \times I$.     * If two identical bulbs are in series with a total voltage given, the voltage across each bulb is halved (assuming they are identical).
• Transformers:     * The transformer equation is $\frac{V_p}{V_s} = \frac{N_p}{N_s}$.     * Example: Primary voltage $V_p = 240\,V$, primary turns $N_p = 50$, secondary turns $N_s = 200$.     * $V_s = V_p \times \frac{N_s}{N_p} = 240 \times \frac{200}{50} = 960\,V$.
• Electromagnetic Induction:     * Induced electromotive force (EMF) is increased by: increasing the speed of rotation, increasing the number of turns in the coil, or using stronger magnets.     * Changing the core to a non-magnetic material (like aluminum) may significantly reduce the effectiveness or not amplify the field like iron does.

Physics: Radioactivity

• Radiation Properties:     * Alpha particles ($\alpha$): Have low penetrating power and are stopped/blocked by a single sheet of paper.     * Background Radiation: The count rate detected when the radioactive source is completely removed (e.g., $10\,counts/minute$).
• Radioactive Elements: Elements like Uranium are naturally radioactive; metals like copper, iron, and aluminum are typically stable.
• Electromagnetic Spectrum: In terms of wavelength, Ultraviolet light has a shorter wavelength and higher frequency compared to infrared, microwaves, and visible light.

Chemistry: Matter, Bonding, and Structure

• Separation Methods:     * Filtration: Used to separate an insoluble solid (precipitate) from a liquid. Example: Separating $AgCl(s)$ from $NaNO_3(aq)$.
• The Periodic Table and Atoms:     * Transition Metals: Characterized by high melting points, high density, and the formation of colored compounds (e.g., green, blue, or red chlorides).     * Atomic Number (Proton Number): The number of protons in the nucleus.     * Mass Number: The sum of protons and neutrons in the nucleus.     * Electronic Configuration: For element Y ($2, 8, 5$), there are 5 valence electrons. To reach stability (noble gas configuration like Argon $2, 8, 8$), it needs to gain 3 electrons, typically forming an ion with a $3-$ charge.
• Stoichiometry Formulas:     * Empirical Formula: Simplest ratio of elements. If a compound is $75\%$ Carbon and $25\%$ Hydrogen:         * Moles of $C = \frac{75}{12} = 6.25$         * Moles of $H = \frac{25}{1} = 25$         * Ratio $C:H = 1:4$, so Empirical Formula is $CH_4$.     * Concentration: $Concentration (mol/dm^3) = \frac{moles}{volume (dm^3)}$.         * Moles of $NaOH$ (Molar Mass $40\,g/mol$) = $\frac{4.00\,g}{40\,g/mol} = 0.1\,mol$.         * Volume = $250\,cm^3 = 0.25\,dm^3$.         * $Concentration = \frac{0.1\,mol}{0.25\,dm^3} = 0.40\,mol/dm^3$.
• Chemical Bonding:     * Covalent Bonding: Involves shared electrons between non-metals (e.g., $HCl$, $CH_4$, Ethene).     * Ionic Bonding: Involves transfer of electrons from metal to non-metal (e.g., $CaCl_2$, $MgO$, $NaCl$).

Chemistry: Chemical Reactions and Organic Chemistry

• Reaction Energetics:     * Endothermic: Reactions that absorb heat (e.g., photosynthesis).     * Exothermic: Reactions that release heat (e.g., combustion, neutralization, respiration).
• Electroplating: In silver plating an earring:     * The Anode must be the pure silver metal (to replace ions in solution).     * The Cathode is the object to be plated (the earring).     * The Electrolyte should contain silver ions (e.g., $AgNO_3$).
• Industrial Chemistry:     * Blast Furnace: Iron oxide (as a solid, $s$) reacts with carbon monoxide to produce molten iron (as a liquid, $l$).     * Ammonia: Used in the production of fertilizers and explosives.
• Organic Chemistry:     * Alkanes: Saturated hydrocarbons containing only single bonds.     * Ethene ($C_2H_4$): An unsaturated hydrocarbon that undergoes addition polymerization to form poly(ethene).     * Methanoic Acid ($HCOOH$): Contains a carbon atom with shared electron pairs forming single bonds with $H$ and $OH$, and a double bond with $O$ (Total electrons shared around Carbon = 8).
• Corrosion: Aluminium is highly resistant to corrosion because it forms a protective, thin layer of aluminium oxide on its surface, which prevents further reaction.
• Chemical Tests:     * Carbon Dioxide ($CO_2$): Turns clear limewater milky/cloudy.     * Oxygen ($O_2$): Relights a glowing splint.     * Water ($H_2O$): Turns blue anhydrous cobalt(II) chloride paper pink.

Biology: Systems and Regulation

• Digestive and Endocrine Systems:     * Blood sugar levels are regulated by the Pancreas (secreting insulin and glucagon) and the Liver (storing glycogen).
• Transport in Plants and Cells:     * Xylem: Transports water and minerals from roots to leaves.     * Phloem: Transports sugars (translocation).     * Osmosis: Demonstrated using Visking tubing (semi-permeable). Iodine molecules can pass through the membrane to react with starch (turning blue-black).
• Respiration and Exercise:     * Yeast Fermentation: Process produces $CO_2$; heat/boiling denatures enzymes, stopping the reaction (the balloon will not inflate if yeast is boiled).     * Lactic Acid: In humans, fast sprinting leads to anaerobic respiration and the build-up of lactic acid in muscles and blood. This level rises during the race and gradually decreases after the race as it is broken down (oxygen debt).
• Excretion and Homeostasis:     * Kidneys: Responsible for removing urea from the blood.     * Thermoregulation (Skin): In response to low temperatures (internal or external), the body reduces sweating and triggers vasoconstriction (narrowing of blood vessels) to minimize heat loss.
• Blood Components:     * Red Blood Cells: Transport oxygen.     * White Blood Cells: Phagocytosis and antibody production.     * Platelets: Essential for blood clotting.     * Plasma: Transports $CO_2$, nutrients, and hormones.

Biology: Reproduction and Ecology

• Human Reproductive Cycle:     * A standard menstrual cycle is 28 days.     * Ovulation (the most fertile period) typically occurs mid-cycle (~Day 14).     * If a cycle starts on June 28, the next period would be due in late July; the window for conception in July would fall roughly between July 10-14.     * Sterilization (Tubal Ligation): Prevents pregnancy in women by blocking the path so sperm cannot meet the egg.
• Sexually Transmitted Diseases (STDs):     * Gonorrhoea: Symptoms include yellow/smelly discharge, pain during urination, and genital swelling. Note: Painless sores (chancres) are typically a symptom of Syphilis, not Gonorrhoea.
• Plant Reproduction: The ovary of a flower develops into a fruit after fertilization.
• Nervous System Coordination:     * The system responsible for reflex actions (like closing eyes during a bright flash) is the nervous system.     * Effectors: Muscles or glands that execute a response to a stimulus after receiving impulses from the central nervous system.
• Environmental Conservation and Ecology:     * Recycling paper helps conserve trees.     * Transpiration: The rate decreases as humidity increases because the concentration gradient for water vapor between the leaf and air is reduced.     * Photosynthesis and Oxygen: In an aquatic environment (pond weed), oxygen levels increase in the presence of light due to photosynthesis, while organisms like snails decrease oxygen through respiration.     * Circulatory System Pattern: Blood flows in a double circuit: Heart → Lungs → Heart → Body (Head/Legs) → Heart.