Why does freshly cut sodium lose its shiny surface within seconds?

Sodium is extremely reactive, so it is oxidised by the oxygen in the air almost immediately.

Why does aluminium resist corrosion even though it is high in the reactivity series?

The oxide layer that forms on aluminium clings firmly to the surface and stops oxygen reaching the metal underneath.

Why does rusting continue to eat into a piece of iron instead of stopping at the surface?

The rust flakes away and exposes fresh iron beneath, which is then oxidised in its turn.

Edexcel GCSE Combined Science Chemistry 1SC0

Key Concepts in Chemistry

Topic overview Formulae, word equations and balanced equations Hazard symbols and assessing risk The changing model of the atom Protons, neutrons and electrons The nucleus, mass number and atomic mass Elements and isotopes Calculating particle numbers and relative atomic mass Mendeleev's periodic table How the modern periodic table is arranged Electronic configuration and the periodic table How ionic bonds form Ions in ionic compounds Formulae of ionic compounds and ionic equations Naming compounds and the ionic lattice Covalent bonds and molecules Dot and cross diagrams for simple molecules Classifying substances and the properties of ionic compounds Properties of simple molecular substances, and forms of carbon Graphite and diamond Fullerenes and graphene Polymers and models of bonding The properties of metals Relative formula mass and percentage composition Empirical and molecular formulae Conservation of mass in closed and open systems Reacting masses from balanced equations Concentration in grams per cubic decimetre Moles and the Avogadro constant Limiting reactants and stoichiometry

States of Matter and Mixtures

Topic overview The three states of matter and changes of state Energy changes during changes of state, and predicting state Pure substances and melting point data Choosing a separation technique Separating a mixture in practice Paper chromatography and interpreting a chromatogram Investigating inks by distillation and chromatography Making water potable

Chemical Changes

Topic overview Acids, alkalis and the pH scale Indicators: litmus, methyl orange and phenolphthalein Hydrogen ion concentration and the pH scale Investigating pH change when neutralising an acid Dilute and concentrated, weak and strong acids Bases and alkalis Reactions of acids, and testing for hydrogen and carbon dioxide Neutralisation and its ionic equation Preparing soluble salts from insoluble and soluble reactants Preparing pure, dry copper sulfate crystals Carrying out an acid-alkali titration Solubility rules Predicting precipitates and preparing an insoluble salt Electrolytes and what electrolysis is Movement of ions and predicting the products of molten electrolysis Electrolysis with inert electrodes Writing half equations Oxidation and reduction at the electrodes Electrolysis of copper sulfate solution Investigating the electrolysis of copper sulfate

Extracting Metals and Equilibria

Topic overview Investigating the reactivity of metals Displacement reactions as redox reactions The reactivity series Ores, oxidation and reduction Choosing a method to extract a metal Biological methods of metal extraction Corrosion resistance and recycling metals Life cycle assessment Reversible reactions and dynamic equilibrium The Haber process and its conditions Changing the position of an equilibrium

Groups in the Periodic Table

Topic overview The groups of the periodic table, and the alkali metals Reactions of the alkali metals with water The pattern in alkali metal reactivity and why it happens Physical properties of the halogens The test for chlorine, and halogens reacting with metals Hydrogen halides, and explaining halogen reactivity Displacement reactions of the halogens Group 0: the noble gases

Rates of Reaction and Energy Changes

Topic overview Investigating the rate of a reaction Measuring rate and interpreting rate graphs Collision theory and factors affecting rate Catalysts and enzymes Exothermic and endothermic changes Bond breaking, bond making and the overall energy change Bond energies, activation energy and reaction profiles

Fuels and Earth Science

Topic overview Hydrocarbons and crude oil Fractional distillation and the fractions Properties of the fractions and homologous series Complete and incomplete combustion Carbon monoxide and soot Pollutants and acid rain Hydrogen and fossil fuels compared Cracking and why it is necessary The Earth's early atmosphere How the oceans formed and how oxygen appeared The test for oxygen and the greenhouse gases Today's atmosphere and evidence for climate change

Extracting Metals and Equilibria

Corrosion resistance and recycling metals

3 things to know
Paper 3

Overview

What corrosion is and how it follows the reactivity series, why gold, sodium and aluminium behave as they do, why rust keeps spreading, and the economic and environmental case for recycling.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is meant by the corrosion of a metal?

Key term

How is a metal’s resistance to oxidation related to its position in the reactivity series?

Key term

Why does a gold ring keep its shine for centuries?

Questions from this subtopic

Each one with the model answer underneath.

1
What is meant by the corrosion of a metal?
Model answer
Corrosion is the gradual destruction of a metal by reaction with substances around it, usually oxygen.
2
How is a metal’s resistance to oxidation related to its position in the reactivity series?
Model answer
The lower a metal lies in the reactivity series, the better it resists oxidation.
3
Why does a gold ring keep its shine for centuries?
Model answer
Gold sits at the bottom of the reactivity series, so it does not react with the oxygen in the air.
4
Why does freshly cut sodium lose its shiny surface within seconds?
Model answer
Sodium is extremely reactive, so it is oxidised by the oxygen in the air almost immediately.
5
Why does aluminium resist corrosion even though it is high in the reactivity series?
Model answer
The oxide layer that forms on aluminium clings firmly to the surface and stops oxygen reaching the metal underneath.
6
Why does rusting continue to eat into a piece of iron instead of stopping at the surface?
Model answer
The rust flakes away and exposes fresh iron beneath, which is then oxidised in its turn.

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Key Concepts in Chemistry

States of Matter and Mixtures

Chemical Changes

Extracting Metals and Equilibria

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Hydrogen is formed.

chloridebromideiodide

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AChlorine is a pale green gas at room temperature.

BBromine is a red-brown liquid at room temperature.

CIodine is a dark grey solid at room temperature.

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A neutral solution has a pH of 7.

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