MYP Science: Acids & Bases (Intro) FAQ

Break it into a checklist:

1. Definitions – acids release H+ ions in water, bases release OH- ions.
2. The pH scale – 0-6 acidic, 7 neutral, 8-14 basic (alkaline).
3. Indicators – litmus, universal indicator, pH probes.
4. Reactions – neutralisation: acid + base → salt + water.
5. Everyday examples – lemon juice, vinegar, soap, bleach. I've taught this unit for years, and the students who do best are the ones who can explain why an indicator changes colour, not just memorise the colour chart.

Quick tip: don't just memorise "low number = acid". Know why — pH is based on the concentration of H+ ions, so more H+ means a lower pH number and a stronger acid. A pH of 1 (battery acid) is far more concentrated in H+ than a pH of 6 (rainwater).

Worked example: Hydrochloric acid + sodium hydroxide → sodium chloride + water.

HCl + NaOH → NaCl + H2O

Notice the pattern: acid + base always gives a salt (named from the acid and metal) plus water. In an MYP investigation, you'd track this using a pH probe or indicator, watching the pH move from acidic, through neutral at 7, to basic as you add excess base.

Common mistake: students record the colour but forget to compare it against a proper universal indicator chart, so their pH estimate is just a guess. Always cross-check colour against the printed scale, and if a digital probe is available, use it to confirm your reading before writing a conclusion.

According to the IB's MYP: From Principles into Practice guide, Sciences assessment uses four criteria (A: Knowing and Understanding, B: Inquiring and Designing, C: Processing and Evaluating, D: Reflecting on Impacts). Acids and bases tasks typically sit under Criterion A for concept questions and B/C for lab-based investigations.

Quick tip: when a question says "explain why the indicator changed colour", don't just restate the colour change. Link it back to the change in H+ or OH- ion concentration — that's the difference between a partial-credit answer and a full-mark one.

Other frequent slips:

• Confusing "neutral" (pH 7) with "neutralised" (the reaction has actually occurred).
• Forgetting that water is produced in every acid-base neutralisation.
• Mixing up litmus colours under exam pressure — red for acid, blue for base, always.

1. Learn the definitions cold (acid, base, neutralisation, indicator).
2. Practise reading and plotting pH data from a real or sample experiment.
3. Write full explanations, not one-word answers, even for short questions.
4. Review your teacher's marked exemplars against the MYP achievement level descriptors for Criterion A and B. On RevisionPrep, topical worksheets on this unit let you practise exactly this kind of explanation-writing with mark-scheme-style feedback.

Quick tip: pick one example you understand deeply rather than five you half-know. If asked to "explain" using an example, a well-explained antacid-and-stomach-acid answer will outscore a vague list of five substances with no reasoning.

In the current DP Chemistry guide (first exams 2025), acids and bases reappear as a full structural topic with quantitative pH calculations and titration curves — skills that assume the qualitative MYP foundation is already solid.

Three things worth checking before the next assessment:

1. Can they define acid, base and neutralisation in their own words?
2. Can they read a pH value off an indicator chart correctly?
3. Can they write a full "explain" answer, not a one-line fact? RevisionPrep's revision notes for MYP Sciences break this topic into short, structured sections that work well alongside classwork for exactly this kind of gap-filling.

Quick tip for parents: before spending money on resources, ask your child to explain neutralisation out loud in their own words. If they can do that clearly, they likely just need more practice questions — which is exactly what structured worksheets are for.