Chemical Equations
The single most common weakness across all four CE reports. Two marks lost: wrong formula, wrong balance.
H20 (zero) instead of H2O (capital letter O for oxygen). Also: writing formulas from memory without balancing — atoms on each side must be equal.
Balance the equation for the combustion of methane: CH4 + O2 → CO2 + H2O
Left: C=1, H=4, O=2 | Right: C=1, H=2, O=3
H and O are unequal — equation is not balanced.
Put 2 in front of H2O → Right now has H=4, O=4. Put 2 in front of O2 → Left O=4.
CH4 + 2O2 → CO2 + 2H2O
Left: C=1, H=4, O=4 | Right: C=1, H=4, O=4 ✓ Balanced
| Process | Word Equation | Chemical Equation |
|---|---|---|
| Photosynthesis | Carbon dioxide + Water → Glucose + Oxygen | 6CO2 + 6H2O → C6H12O6 + 6O2 |
| Aerobic respiration | Glucose + Oxygen → Carbon dioxide + Water + Energy | C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy |
| Anaerobic (animals) | Glucose → Lactic acid + Small energy | C6H12O6 → 2C3H6O3 + Energy |
| Anaerobic (yeast) | Glucose → Ethanol + Carbon dioxide + Small energy | C6H12O6 → 2C2H5OH + 2CO2 + Energy |
| Neutralisation | Acid + Base → Salt + Water | HCl + NaOH → NaCl + H2O |
| Combustion (carbon) | Carbon + Oxygen → Carbon dioxide | C + O2 → CO2 |
Never change the subscript in a formula to balance. H2O stays H2O — you balance by adding a number in front of the whole formula (the coefficient).
Electronics & Circuit Symbols
Students lost marks drawing symbols from memory incorrectly. The CE 2023 report listed this as a major failure point.
"Candidates could not draw the symbols for a resistor, diode, cell, or LED correctly. Many drew a zigzag for the resistor instead of a rectangle."
The zigzag resistor symbol is American (ANSI). BECE (WAEC Ghana) uses the rectangle. Writing a zigzag will lose marks.
Draw and describe a forward-biased diode circuit.
Forward biasing is when the positive terminal of the supply is connected to the p-type (anode) side of the diode, allowing current to flow through the junction.
Ecology & Food Webs
In 2023, the examiner said food webs drawn without arrows earned zero marks. Arrow direction is the most repeated error.
Arrows show the direction of energy flow — from the organism being eaten TO the organism doing the eating. Grass → Grasshopper (not ←). A food web with no arrows, or arrows reversed, scores zero.
Grass → Grasshopper → Frog → Snake → Hawk. Identify the trophic levels.
- Arrows point FROM prey TO predator
- Every organism has a label (common name)
- Producers at the bottom of the diagram
- Apex predator at the top with no outgoing arrow
- At least one organism at each trophic level
- No arrows at all (zero marks for diagram)
- Arrows reversed (pointing prey ← predator)
- Missing organisms (incomplete chain)
- No title for the diagram
- Confusing food chain with food web
A food chain is a single linear sequence (A → B → C). A food web is multiple interlocking food chains in the same ecosystem — it shows all feeding relationships together.
Human Reproductive System
Parts and functions appear every year. The examiner specifically flagged HIV/AIDS being listed as a reproductive STI — it is not.
The infectious diseases of the reproductive system are gonorrhea and syphilis. HIV/AIDS is not specific to the reproductive system. Listing it instead of gonorrhea or syphilis loses the mark.
- Testes — produce sperm and testosterone
- Epididymis — stores and matures sperm
- Vas deferens — carries sperm from epididymis to urethra
- Seminal vesicles — produce seminal fluid to nourish sperm
- Prostate gland — adds alkaline fluid to semen
- Urethra — tube for sperm and urine to leave the body
- Penis — organ for depositing sperm
- Ovaries — produce eggs (ova) and hormones (oestrogen, progesterone)
- Fallopian tubes (oviducts) — carry egg from ovary to uterus; site of fertilisation
- Uterus (womb) — where foetus develops during pregnancy
- Cervix — lower narrow part of uterus; dilates during childbirth
- Vagina — birth canal; receives penis during intercourse
| STI | Causative Organism | Symptoms | Prevention |
|---|---|---|---|
| Gonorrhea | Neisseria gonorrhoeae (bacterium) | Painful urination, discharge, swollen joints | Abstinence, condom use, treat early with antibiotics |
| Syphilis | Treponema pallidum (bacterium) | Painless sore (chancre), rash, organ damage if untreated | Abstinence, condom use, penicillin treatment |
- Peer pressure and desire to experiment
- Lack of sex education
- Poverty (transactional sex)
- Alcohol and drug influence
- Abuse / lack of parental supervision
- School dropout — interrupted education
- Health risks to mother and baby
- Poverty cycle — reduced earning potential
- Social stigma and mental health issues
- Unsafe abortions
Respiration
Candidates confused aerobic and anaerobic, and could not state the word or chemical equations for either.
| Feature | Aerobic | Anaerobic |
|---|---|---|
| Oxygen needed? | Yes — requires O2 | No — no O2 required |
| Products (animals) | CO2 + H2O + Energy | Lactic acid + Energy |
| Products (yeast) | CO2 + H2O + Energy | Ethanol + CO2 + Energy |
| Energy released | Large (38 ATP) | Small (2 ATP) |
| Location in cell | Mitochondria | Cytoplasm |
| When it occurs | Normal body activity | Intense exercise; oxygen debt |
| In brewing/baking | Not used | Yeast fermentation (bread, beer) |
Aerobic respiration occurs in the presence of oxygen and releases a large amount of energy, while anaerobic respiration occurs without oxygen and releases a smaller amount of energy, producing lactic acid in animals.
Agriculture & Soil
Farm tools appear yearly. Swollen shoot disease and soil erosion prevention were specifically flagged in 2023.
| Farm Tool | Primary Use | Distinctive Feature |
|---|---|---|
| Cutlass | Clearing bush, harvesting, chopping plant material | Long flat blade with handle — general-purpose cutting |
| Hoe / Mattock | Tilling soil, weeding, mounding | Metal blade at right angle to handle — used for breaking soil |
| Hand Fork | Loosening soil around plants, removing weeds | Small fork with 3–4 prongs — used near delicate roots |
| Peg / Dibber | Making holes in soil for planting seeds or seedlings | Pointed stick or T-shaped tool — used for transplanting |
| Watering Can | Applying water to plants in nursery or garden beds | Rose (perforated head) distributes water gently |
| Pruning Shears | Cutting back branches and dead plant material | Spring-loaded scissors — keeps blades clean and sharp |
- Mulching — cover soil with organic material to reduce runoff
- Cover cropping — plant ground-cover plants between main crops
- Contour plowing — plow across the slope, not down it
- Terracing — cut step-like ridges into hillsides
- Afforestation — plant trees to hold soil with roots
- Strip cropping — alternate strips of crops reduce wind/water erosion
- Loss of topsoil — removes the nutrient-rich layer
- Exposed subsoil — less fertile, poor root penetration
- Reduced water retention — plants suffer drought stress
- Reduced crop yield and poor growth
- Root damage — physical removal of shallow-rooted plants
Physics: Electricity & Ohm's Law
Answers without units, and formulas not stated before use — flagged by the examiner in 2018, 2021, and 2023.
I = Current (Amperes, A)
R = Resistance (Ohms, Ω)
A resistor has a resistance of 15 Ω. A current of 2 A flows through it. Calculate the potential difference across the resistor.
| Feature | Series Circuit | Parallel Circuit |
|---|---|---|
| Current | Same through all components | Splits — different through each branch |
| Voltage | Splits across components: V = V1 + V2 | Same across each branch |
| Total resistance | Rtotal = R1 + R2 + … | 1/Rtotal = 1/R1 + 1/R2 + … |
| If one component fails | Whole circuit stops | Others continue working |
| Example | Old Christmas lights | House wiring, mains appliances |
Writing 30 instead of 30 V loses the unit mark. The examiner flagged this in 2018 and 2023. Always write the unit after every numerical answer: V (volts), A (amperes), Ω (ohms), W (watts), J (joules).
Laboratory Skills
Confusing observation with inference was the most cited lab error. Command word meanings are also regularly tested.
"The solution is acidic."
"The gas is carbon dioxide."
"The substance dissolved because it is ionic."
"Blue litmus paper turned red."
"A colourless gas was given off which turned limewater milky."
"The solid disappeared and the solution became clear."
When a question says "State your observation", describe only what can be seen, smelled, or heard. Do not explain why. The explanation belongs in an inference or conclusion.
| Command Word | What to do | How much to write |
|---|---|---|
| State | Give a brief fact — no explanation needed | 1 sentence |
| Explain | Give the fact AND the reason/mechanism | 2–3 sentences |
| Describe | Write what happens or what it looks like, in sequence | 2–4 sentences |
| Suggest | Give a plausible reason — acceptable if logically argued | 1–2 sentences |
| Compare | State both a similarity AND a difference between two things | 1 point of each |
| Calculate | Show your working, give answer with unit | All steps shown |
| Draw / Sketch | Draw with title, labelled parts, and arrows where relevant | Full diagram |
- A descriptive title
- All parts labelled (lines to each part)
- Directional arrows where movement is shown
- Correct proportions (no squashed shapes)
- No title on the diagram
- Missing labels on parts
- Food web arrows missing or reversed
- Circuit diagrams with broken wires
Science Spelling & Exam Checklist
Scientific spelling errors cost marks every single year. These are the exact words the examiner listed.
Pre-Exam Checklist
- I can write and balance photosynthesis, respiration, and neutralisation equations
- I can draw all circuit symbols correctly (rectangle for resistor, diode direction)
- I know the difference between forward and reverse bias
- I know food web arrows point FROM prey TO predator
- I can name all parts of male and female reproductive systems
- The STIs for the reproductive system are gonorrhea and syphilis — not HIV/AIDS
- I can state the difference between aerobic and anaerobic respiration in one sentence
- I know Ohm's Law (V = IR) and can rearrange it
- I always write units after every numerical answer in Physics
- I know the difference between observation and inference in lab questions
- Swollen shoot disease: cocoa + virus + mealybug vector + rouging
- I checked the spelling of: neutralisation, photosynthesis, chromosome, chlorophyll
State the formula or definition before you use it. A Physics answer that shows V = IR before substituting values earns method marks even if the final number is wrong. Starting with only the numbers earns nothing if the answer is wrong.