Key term
Edexcel GCSE Combined Science Chemistry 1SC0
Key Concepts in Chemistry
Topic overviewFormulae, word equations and balanced equationsHazard symbols and assessing riskThe changing model of the atomProtons, neutrons and electronsThe nucleus, mass number and atomic massElements and isotopesCalculating particle numbers and relative atomic massMendeleev's periodic tableHow the modern periodic table is arrangedElectronic configuration and the periodic tableHow ionic bonds formIons in ionic compoundsFormulae of ionic compoundsNaming compounds and the ionic latticeCovalent bonds and moleculesDot and cross diagrams for simple moleculesClassifying substances and the properties of ionic compoundsProperties of simple molecular substances, and forms of carbonGraphite and diamondFullerenes and graphenePolymers and models of bondingThe properties of metalsRelative formula mass and percentage compositionEmpirical and molecular formulaeConservation of mass in closed and open systemsReacting masses from balanced equationsConcentration in grams per cubic decimetre
States of Matter and Mixtures
Topic overviewThe three states of matter and changes of stateEnergy changes during changes of state, and predicting statePure substances and melting point dataChoosing a separation techniqueSeparating a mixture in practicePaper chromatography and interpreting a chromatogramInvestigating inks by distillation and chromatographyMaking water potable
Chemical Changes
Topic overviewAcids, alkalis and the pH scaleIndicators: litmus, methyl orange and phenolphthaleinInvestigating pH change when neutralising an acidBases and alkalisReactions of acids, and testing for hydrogen and carbon dioxideNeutralisation and its ionic equationPreparing soluble salts from insoluble and soluble reactantsPreparing pure, dry copper sulfate crystalsCarrying out an acid-alkali titrationSolubility rulesPredicting precipitates and preparing an insoluble saltElectrolytes and what electrolysis isMovement of ions and predicting the products of molten electrolysisElectrolysis with inert electrodesElectrolysis of copper sulfate solutionInvestigating the electrolysis of copper sulfate
Extracting Metals and Equilibria
Groups in the Periodic Table
Topic overviewThe groups of the periodic table, and the alkali metalsReactions of the alkali metals with waterThe pattern in alkali metal reactivity and why it happensPhysical properties of the halogensThe test for chlorine, and halogens reacting with metalsHydrogen halides, and explaining halogen reactivityDisplacement reactions of the halogensGroup 0: the noble gases
Rates of Reaction and Energy Changes
Fuels and Earth Science
Topic overviewHydrocarbons and crude oilFractional distillation and the fractionsProperties of the fractions and homologous seriesComplete and incomplete combustionCarbon monoxide and sootPollutants and acid rainHydrogen and fossil fuels comparedCracking and why it is necessaryThe Earth's early atmosphereHow the oceans formed and how oxygen appearedThe test for oxygen and the greenhouse gasesToday's atmosphere and evidence for climate change
Key Concepts in Chemistry
Reacting masses from balanced equations
- 1 thing to know
- Papers 3 and 4
Overview
What a reacting mass calculation needs, why the equation must be balanced, and worked masses for calcium carbonate decomposing, magnesium burning, iron(III) oxide reduced and hydrogen burning.
What you need to know
Answer each one before you reveal it.
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Questions from this subtopic
Each one with the model answer underneath.
- 1
What information is needed before the mass of a product can be calculated from the mass of a reactant?
Model answer
The balanced equation for the reaction and the relative formula masses of the substances involved.
- 2
Why must an equation be balanced before reacting masses are calculated?
Model answer
The balancing numbers give the ratio in which the substances react, and the wrong ratio gives the wrong mass.
- 3
In CaCO₃ → CaO + CO₂, calculate the mass of calcium oxide formed from 50 g of calcium carbonate. Relative formula masses: CaCO₃ = 100, CaO = 56.
Model answer
50 ÷ 100 × 56 = 28 g.
- 4
In CaCO₃ → CaO + CO₂, calculate the mass of carbon dioxide released from 50 g of calcium carbonate. Relative formula masses: CaCO₃ = 100, CO₂ = 44.
Model answer
50 ÷ 100 × 44 = 22 g.
- 5
In 2Mg + O₂ → 2MgO, calculate the mass of magnesium oxide formed from 4.8 g of magnesium. Relative atomic masses: Mg = 24, O = 16.
Model answer
48 g of magnesium gives 80 g of oxide, so 4.8 g gives 8.0 g.
- 6
In 2Mg + O₂ → 2MgO, calculate the mass of oxygen that combines with 4.8 g of magnesium, given that 8.0 g of oxide is formed.
Model answer
8.0 − 4.8 = 3.2 g.
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