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CAMEROON GCE O-LEVEL CHEMISTRY — Q&A NOTES (CLICKUP EDITION)
1. Introduction to Chemistry
Q1: What is Chemistry?
Chemistry is the branch of science that studies the composition, structure, properties, and reactions of matter.
Q2: What is matter?
Matter is anything that has mass and occupies space (e.g., air, water, stone).
Q3: What are the three states of matter?
Solid, liquid, and gas.
Q4: What is the difference between physical and chemical changes?
- Physical change: No new substance is formed (e.g., melting ice).
- Chemical change: A new substance is formed (e.g., rusting iron, burning wood).
2. Atomic Structure
Q5: What are the three particles found in an atom?
Protons, neutrons, and electrons.
Q6: Where are these particles located?
- Protons → nucleus
- Neutrons → nucleus
- Electrons → shells or energy levels around the nucleus
Q7: What is the atomic number?
The number of protons in an atom.
Q8: What is the mass number?
The sum of protons and neutrons.
Q9: What are isotopes?
Atoms of the same element with the same number of protons but different numbers of neutrons.
Q10: What is an ion?
A charged atom formed by gaining or losing electrons.
3. The Periodic Table
Q11: What is the periodic table?
A table arranging elements in order of increasing atomic number.
Q12: What are groups and periods?
- Groups: Vertical columns
- Periods: Horizontal rows
Q13: What are properties of Group I elements (Alkali metals)?
Very reactive metals, soft, form +1 ions.
Q14: What are properties of Group VII (Halogens)?
Very reactive non-metals, form –1 ions, exist as diatomic molecules (e.g., Cl₂).
4. Chemical Bonding
Q15: What are the main types of chemical bonds?
Ionic, covalent, and metallic bonds.
Q16: What is ionic bonding?
Transfer of electrons from a metal to a non-metal to form ions.
Q17: What is covalent bonding?
Sharing of electron pairs between non-metals.
Q18: What is metallic bonding?
Positive metal ions surrounded by a “sea of delocalized electrons.”
5. Chemical Equations and Stoichiometry
Q19: What is a chemical equation?
A symbolic representation of a chemical reaction.
Q20: Why do we balance equations?
To obey the law of conservation of mass.
Q21: What is the mole?
A unit for counting particles; 1 mole = 6.02 × 10²³ particles.
Q22: What is molar mass (Mr)?
The mass of one mole of a substance.
6. Acids, Bases, and Salts
Q23: What is an acid?
A substance that releases H⁺ ions in water (e.g., HCl, H₂SO₄).
Q24: What is a base?
A substance that releases OH⁻ ions in water (e.g., NaOH).
Q25: What is a salt?
A compound formed when the hydrogen in an acid is replaced by a metal or ammonium ion.
Q26: What is neutralization?
Acid + Base → Salt + Water
Q27: What are indicators?
Substances that change color in acids and bases (e.g., litmus, phenolphthalein).
7. Water and Air
Q28: What are the major gases in air?
Nitrogen (78%), Oxygen (21%), Others (1%).
Q29: What are the common impurities in water?
Dissolved salts, suspended particles, microorganisms.
Q30: How is water purified?
Sedimentation → Filtration → Chlorination.
Q31: What is hard water?
Water that does not easily form lather with soap.
Q32: What causes hardness?
Calcium and magnesium salts.
8. Carbon and Organic Chemistry
Q33: What is organic chemistry?
The study of carbon compounds (except CO₂, CO, carbonates).
Q34: What is a homologous series?
A group of organic compounds with similar structures and chemical properties, and each member differs by CH₂.
Q35: What are alkanes?
Saturated hydrocarbons with general formula CₙH₂ₙ₊₂.
Q36: What are alkenes?
Unsaturated hydrocarbons with at least one C=C double bond and formula CₙH₂ₙ.
Q37: What is isomerism?
Compounds with the same molecular formula but different structural formulae.
9. Energy Changes in Chemical Reactions
Q38: What is an exothermic reaction?
A reaction that releases heat (e.g., combustion).
Q39: What is an endothermic reaction?
A reaction that absorbs heat (e.g., photosynthesis).
10. Metals and Reactivity
Q40: What is the reactivity series?
An arrangement of metals according to their reactivity (K, Na, Ca, Mg, Al… down to Au).
Q41: What is oxidation?
Gain of oxygen or loss of electrons.
Q42: What is reduction?
Loss of oxygen or gain of electrons.
Q43: What is corrosion?
The gradual destruction of metals by reacting with substances in the environment (e.g., rusting of iron).
11. Extraction and Uses of Metals
Q44: How is iron extracted?
By reduction of iron ore in a blast furnace.
Q45: What are the uses of aluminium?
Airplane bodies, cooking utensils, electrical cables (light and corrosion-resistant).
12. Rates of Reaction
Q46: What factors affect rate of reaction?
Temperature, concentration, surface area, catalysts.
Q47: What is a catalyst?
A substance that increases the rate of reaction without being used up.
13. Pollution and Environmental Chemistry
Q48: What are common air pollutants?
CO, SO₂, NOₓ, smoke.
Q49: What are effects of pollution?
Global warming, acid rain, respiratory diseases.
Q50: How can pollution be reduced?
Use of catalytic converters, planting trees, using renewable energy.