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GCSE Chemistry · key term
A starting substance that is changed during a chemical reaction.
Used by AQA, Edexcel and OCR
Specification 4.3.1.1, 4.6.2.1 · Paper 1, Paper 2
A substance present at the start of a chemical reaction.
Revise: Conservation of MassIt applies to the total mass of every reactant and every product involved in the reaction. The products can have very different properties from the reactants, but they contain the same collection of atoms.
Specification 0.2, 1.47, 5.25C · Paper 1, Paper 2
A starting substance that undergoes a chemical change during a chemical reaction.
Revise: Word EquationsPut the reactants on the left, the products on the right, and connect the two sides with an arrow.
The starting substance or substances in a chemical reaction, written on the left of a chemical equation.
A substance present at the start of a chemical reaction and changed during the reaction.
A substance that is used up during a chemical reaction.
Specification C1.1b, C3.1b, C3.1i · Paper 1 (Foundation), Paper 3 (Higher)
A starting substance in a chemical reaction.
Revise: Physical vs Chemical ChangesIn a chemical reaction, reactant particles collide. Collisions at an appropriate energy can lead to atoms or ions being rearranged. Existing combinations change and new combinations form, producing product particles with different chemical identities.
A substance present at the start of a chemical reaction and changed by it.
A substance present at the start of a chemical reaction and changed during the reaction.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: Writing balanced equationsConsequently, every atom present among the reactants must also be present among the products. This is the particle-level explanation of the conservation of mass: the total mass of the products equals the total mass of the reactants for the complete reaction system.
A starting substance that is changed into products during a chemical reaction.
A starting substance that is changed during a chemical reaction and is written on the left of the reaction arrow.
A starting substance that takes part in a chemical reaction.
Use the reversible-reaction symbol , not a single arrow, when the products can reform the reactants.
Place every reactant to the left of the arrow and every product to the right, even if the question describes the products first.
Read reaction language carefully: “reacts with” usually joins reactants, while “forms”, “produces” or “makes” introduces products.
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