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
Empirical and molecular formulae
- 1 thing to know
- Papers 3 and 4
Overview
Empirical formulae of glucose, hydrogen peroxide and butane, going from empirical formula and relative molecular mass to molecular formula, and the crucible experiment that finds the formula of magnesium oxide.
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
Give the empirical formula of glucose, C₆H₁₂O₆.
Model answer
CH₂O.
- 2
Give the empirical formula of hydrogen peroxide, H₂O₂.
Model answer
HO.
- 3
Give the empirical formula of butane, C₄H₁₀.
Model answer
C₂H₅.
- 4
How is a molecular formula obtained from an empirical formula and a relative molecular mass?
Model answer
Divide the relative molecular mass by the empirical formula mass and multiply every number in the formula by the answer.
- 5
A compound has the empirical formula CH₂ and a relative molecular mass of 42. Determine its molecular formula. Relative atomic masses: C = 12, H = 1.
Model answer
CH₂ has a mass of 14 and 42 ÷ 14 = 3, so the molecular formula is C₃H₆.
- 6
A compound has the empirical formula CH₂O and a relative molecular mass of 180. Determine its molecular formula.
Model answer
CH₂O has a mass of 30 and 180 ÷ 30 = 6, so the molecular formula is C₆H₁₂O₆.
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