AQA GCSE Chemistry — Quantitative and Chemical Changes flashcards
10 of 76 cards free to study here · 2 topics · the whole deck is built into Willys
Topics 4.3 and 4.4 of AQA GCSE Chemistry: conservation of mass, moles, concentration, yield and atom economy, gas volumes, the reactivity series, redox, acids, salts and pH, and electrolysis. Higher Tier and Chemistry-only cards are marked.
Learn deck · part of AQA GCSE Chemistry · written against: AQA GCSE Chemistry (8462) specification, version 1.2, 16 January 2026; Higher Tier and separate-science-only cards marked on the front. Updated 2026-10-10.
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Why must a balanced equation have the same number of atoms of each element on both sides?The law of conservation of mass: a reaction only rearranges atoms, creating or destroying none, so the products weigh exactly as much as the reactants.Quantitative Chemistry › Conservation of Mass and Measurement
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Magnesium ribbon is heated in an open crucible and the mass of solid increases. Explain this using 2Mg + O₂ → 2MgO.The magnesium combines with oxygen from the air, and the mass of that oxygen is now part of the solid magnesium oxide.Quantitative Chemistry › Conservation of Mass and Measurement
Why: mass is still conserved; the gain is oxygen that was not weighed at the start. -
Calcium carbonate is heated in an open tube and the mass of solid falls. Explain this.It decomposes, CaCO₃ → CaO + CO₂, and the carbon dioxide gas escapes into the air, leaving only calcium oxide as the solid.Quantitative Chemistry › Conservation of Mass and Measurement
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In 2HCl, what does the large 2 mean, and what does the small subscript 2 in MgCl₂ mean?The large 2 multiplies the whole formula: two units of HCl. The subscript 2 means two chlorine atoms within one unit of MgCl₂.Quantitative Chemistry › Conservation of Mass and Measurement
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Balance the equation Al + O₂ → Al₂O₃.4Al + 3O₂ → 2Al₂O₃Quantitative Chemistry › Conservation of Mass and Measurement
Why: six oxygen atoms on each side needs 3O₂ and 2Al₂O₃, and 2Al₂O₃ then needs four aluminium atoms. -
Iron oxide is heated with carbon to extract iron. In terms of oxygen, which substance is oxidised and which is reduced?Iron oxide is reduced (it loses oxygen) and carbon is oxidised (it gains oxygen).Chemical Changes › Reactivity of Metals
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Put potassium, magnesium, copper, zinc, sodium, calcium, iron and lithium in order of reactivity, most reactive first.Potassium, sodium, lithium, calcium, magnesium, zinc, iron, copper.Chemical Changes › Reactivity of Metals
Why: the more easily a metal forms its positive ion, the more reactive it is. -
How does copper react with water and with dilute hydrochloric acid at room temperature?It does not react with either.Chemical Changes › Reactivity of Metals
Why: copper is below hydrogen in the reactivity series, so it cannot displace hydrogen. -
Magnesium is put into cold water and into dilute hydrochloric acid. What would you see in each?In cold water almost nothing happens (a very slow reaction); in the acid there is rapid fizzing as hydrogen forms and the magnesium dissolves.Chemical Changes › Reactivity of Metals
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Why is the reactivity of a metal linked to how easily it forms a positive ion?When metals react, their atoms lose outer electrons to form positive ions; the more easily a metal does this, the more reactive it is.Chemical Changes › Reactivity of Metals
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Review status: Second-reader reviewed, with corrections applied.
Checked against:
- Topic outline follows the AQA GCSE Chemistry (8462) specification, version 1.2 (16 January 2026) (outline only; no specification text reproduced).
- OpenStax Chemistry 2e, consulted as a reference; no text copied.
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