MYP · Chemistry MYP Year 4

Chemical Reactions and Bonding

MYP Year 4 Chemistry — Chemical Reactions and Bonding

29 min readStandardCore unit — assessed through Criterion A (knowing & understanding) data-response questions and Criterion C practical investigations; thermal decomposition and mass-conservation graphs are the most repeated question types

This unit is where MYP examiners stop asking you to describe and start asking you to deduce — from a table of masses, a decomposition temperature trend, or an equation you've never seen before. The four skills that actually get marked: naming a reaction type from evidence (not guessing), predicting what a reactive metal will do, explaining bonding in terms of electrons (not vague 'attraction'), and proving mass is conserved when you balance an equation. Get comfortable with $C a C O_{3}$ , $H_{2} O_{2}$ and displacement reactions — they appear in almost every paper.

Overview

Five ideas run through this whole unit and they build on each other. You classify a reaction by what happens to reactants and products (types of reactions). You predict whether a reaction will even happen using the reactivity series. You explain why substances behave as they do using bonding (electron transfer, sharing, or delocalisation). You describe what's reacting using correct formulas. And you prove nothing is lost or gained using balanced equations and conservation of mass.

Every 'deduce' question in this unit wants you to read a pattern from data or an equation — not recall a fact from memory.
Thermal decomposition ( $C a C O_{3}$ , $C u (O H)_{2}$ , $K C l O_{3}$ , $H_{2} O_{2}$ , $H g O$ ) is the single most-tested reaction across past papers.
Bonding questions almost always ask for electron behaviour (transferred, shared, or delocalised) — 'strong attraction' alone earns zero marks.

Mind map of Chemical Reactions and Bonding centred on Chemical Reactions & Bonding.

Command terms that decide your marks in this unit

Command term	What it demands	AO	Mark-earning move
Identify	Name the substance/relationship/pattern directly from given data — no explanation needed.	Criterion A	One correct word or formula = full marks; adding wrong reasoning doesn't cost marks but doesn't earn them either.
State	Give a short, precise answer with no justification required.	Criterion A	Marker wants the fact only — e.g. 'ionic bond' or '+1 charge', not a sentence of explanation.
Describe	Give a detailed account of what happens, including the trend/pattern shown by data.	Criterion A/C	Must reference the actual numbers or observation, not just 'it increases'.
Deduce	Reach a conclusion using evidence given in the question — the answer isn't stated anywhere, you build it.	Criterion C	You must show the working/reasoning link, e.g. ratio calculation, or the mark for the conclusion alone is withheld.
Explain	Give reasons — state what happens AND why, usually referencing particles/electrons/energy.	Criterion A/C	A correct fact with no mechanism (e.g. 'because they attract') scores half marks at best.
Construct	Build a balanced equation, graph or model from raw information.	Criterion C	Missing state symbols or unbalanced coefficients lose the mark even if the formulas are right.
Justify	Support a claim with evidence or reasoning drawn directly from the source given.	Criterion C/D	You must quote the equation/data, not just assert the conclusion.

Key point

Almost every mark loss in this unit comes from one habit: stating a fact without linking it to the evidence given. If a question gives you numbers, an equation or an observation, your answer must reference it directly.

Overview

Chemical Reactions and Bonding

Overview

The shape of the chapter

Command terms that decide your marks in this unit