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
Formulae, word equations and balanced equations
- 2 things to know
- Papers 3 and 4
Overview
Formulae of oxygen, the diatomic elements, ammonia, methane, common acids and ions such as sulfate, carbonate, hydroxide and ammonium, writing word equations, and balancing equations with state symbols without changing any formula.
What you need to know
Answer each one before you reveal it.
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Key term
Which seven elements exist as diatomic molecules, and what does diatomic mean?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is the chemical formula of a molecule of oxygen gas?
Model answer
Oxygen gas has the formula O₂.
- 2
Which seven elements exist as diatomic molecules, and what does diatomic mean?
Model answer
Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine are diatomic, meaning each molecule contains two atoms joined together.
- 3
State the formulae of ammonia and methane.
Model answer
Ammonia is NH₃ and methane is CH₄.
- 4
Give the formulae of sulfuric acid, nitric acid and hydrochloric acid.
Model answer
They are H₂SO₄, HNO₃ and HCl.
- 5
State the formula and charge of the sulfate ion and of the carbonate ion.
Model answer
Sulfate is SO₄²⁻ and carbonate is CO₃²⁻.
- 6
What are the formulae of the hydroxide ion and the ammonium ion?
Model answer
Hydroxide is OH⁻ and ammonium is NH₄⁺.
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