Last-Minute Revision: O Level Chemistry 5070 Notes (2025) - Your Emergency A* Plan

Exam tomorrow? Don't panic. This is your last-minute revision guide for O Level Chemistry 5070. We've condensed the entire 2025 syllabus into the absolute essentials you need to know. These emergency notes focus on high-mark topics, common exam questions, and simple tricks to help you score maximum points when time is critical. Follow this guide, stay calm, and you can significantly boost your grade.

The 24-Hour Last-Minute Study Plan

This timeline is designed for maximum retention. Stick to it.

Condensed O Level Chemistry 5070 Notes (2025 Syllabus)

These are the topics that appear EVERY year. Master these first.

1. Stoichiometry & The Mole (The Non-Negotiable)

This is the biggest mark-earner in Paper 4. You cannot afford to skip it.

• Mole Formula: moles = mass / M_r
• Concentration: conc. = moles / volume (dm³)
• Gas Volume: moles = volume (dm³) / 24
• LAST MINUTE TIP: Always check if your equation is balanced first. The most common mistake is calculating with an unbalanced equation.

Need a quick calc refresher? Speed through our Moles Worksheet.

2. Acids, Bases & Salts (Guaranteed Questions)

• Three Salt Preparations:
  1. Titration: Acid + Alkali (soluble salts)
  2. Precipitation: Two soluble salts (insoluble salts)
  3. Acid + Metal/Carbonate/Oxide: (soluble salts)
• Tests for Gases:
  • Hydrogen: Squeaky pop with a lighted splint.
  • Oxygen: Relights a glowing splint.
  • Carbon Dioxide: Turns limewater cloudy.
  • Chlorine: Bleaches damp litmus paper.
• LAST MINUTE TIP: For "method of preparation" questions, the first step is always to identify if the salt is soluble or insoluble.

3. Organic Chemistry (Easy to Memorize)

• Homologous Series: Know the trends (melting point, boiling point, viscosity, flammability).
• Tests:
  • Alkane vs. Alkene: Bromine water. Alkene decolorizes it (orange to colorless).
  • Alcohol: Burns with a clean blue flame.
• LAST MINUTE TIP: You can identify the homologous series by the ending: -ane (alkane), -ene (alkene), -ol (alcohol).

4. Electrochemistry (Master the Rules)

• For Molten Compounds: Metal is formed at the cathode (-), non-metal at the anode (+).
• For Aqueous Solutions: It gets tricky. Memorize this order of discharge:
  • At Cathode: If metal is above H in reactivity series, H₂ is produced. If below, the metal is produced.
  • At Anode: If halide ions (Cl-, Br-, I-) are present, the halogen is formed. Otherwise, O₂ from OH- is produced.
• LAST MINUTE TIP: For concentrated NaCl, Cl₂ is produced at the anode, not O₂. This is a classic trick question.

If electrolysis confuses you, our 15-minute Electrochemistry Masterclass can save you.

5. The Periodic Table (Focus on Trends)

• Group I (Alkali Metals): Reactivity increases DOWN the group. Low density, soft, violent reaction with water.
• Group VII (Halogens): Reactivity decreases DOWN the group. Color and state change (F₂ pale yellow gas, Cl₂ green gas, Br₂ red-brown liquid, I₂ grey solid).
• Transition Metals: High melting points, form colored compounds, act as catalysts.
• LAST MINUTE TIP: Explain trends in terms of atomic size and ease of losing/gaining electrons.

Must-Know Formulas & Equations

Write these down on a cheat sheet and review them every hour:

What You MUST Write in Your Exam (Keyword Checklist)

Examiners look for specific phrases. Use these to grab easy marks:

• For rate of reaction graphs: "The curve becomes less steep because the concentration of reactants decreases / the surface area gets used up."
• For endothermic/exothermic: "Temperature decreases because energy is taken in from the surroundings / Temperature increases because energy is released to the surroundings."
• For catalysts: "It provides an alternative pathway with a lower activation energy."
• For electrolysis: "At the cathode, reduction occurs. At the anode, oxidation occurs."

Common Pitfalls to Avoid

Don't lose easy marks on these:

1. Missing Units: Always include units in your final answer (g, mol, dm³, kJ/mol).
2. Incorrect State Symbols: Use (s), (l), (g), (aq) in chemical equations.
3. Vague Language: Say "the mass decreases" not "it gets smaller."
4. Unbalanced Equations: Always double-check atom count on both sides.
5. Misreading Questions: Underline command words: state, explain, describe, suggest.

Final 2-Hour Emergency Drill

In your final two hours, do this:

1. Quick Past Paper Scan (60 mins): Take one recent past paper. Don't write answers. Just read each question and mentally note what topic it's testing and the key steps to solve it.
2. Keyword Review (30 mins): Go through the "What You MUST Write" section above. Say the phrases out loud.
3. Formula & Definition Recall (20 mins): Cover your formula sheet and try to write all formulas from memory.
4. Relax (10 mins): Breathe. You have prepared under pressure. Trust your knowledge.

Last-Minute Mindset Tips

• Time Management: Spend about 1 minute per mark. If stuck, move on and return later.
• Show Working: You get method marks even if your final answer is wrong.
• Attempt Every Question: A blank answer gets zero. A wrong answer might get method marks.
• Stay Hydrated: Your brain needs water to function at its best.

Need More Than Last-Minute Help?

If you're reading this with more than a week to go, you have time for a more solid foundation. Our O Level Chemistry 5070 Crash Course can still help you turn things around with live sessions, personalized feedback, and a structured plan.

Conclusion: You Can Do This

You have the essential last-minute revision notes for O Level Chemistry 5070. You know the high-yield topics, the common pitfalls, and the exam strategy. Now, take a deep breath. Your goal isn't perfection—it's to maximize your score with the time you have left. Go into that exam room with confidence, write clearly, and apply what you've just learned. Good luck!

P.S. If you have 10 minutes right now, quickly scan our Ultimate Guide for any topics you're unsure about. It could be the quickest 5 marks you ever earn.