Which takes longer to disappear on water, a piece of lithium or an identical piece of potassium?

The lithium takes longer, because lithium is the less reactive of the two metals.

Why is potassium the only one of lithium, sodium and potassium whose hydrogen normally catches fire on water?

Potassium reacts fastest and releases heat quickly enough to set the hydrogen alight.

Rubidium lies below potassium in group 1. Predict how it behaves when dropped into water.

Rubidium reacts even more violently than potassium, because reactivity increases further down the group.

Caesium lies below rubidium in group 1. Predict how vigorous its reaction with water is.

Caesium reacts more violently still, and the reaction is explosive.

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 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

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 Investigating pH change when neutralising an acid 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 Electrolysis of copper sulfate solution Investigating the electrolysis of copper sulfate

Extracting Metals and Equilibria

Topic overview Investigating the reactivity of metals The reactivity series Ores, oxidation and reduction Choosing a method to extract a metal Corrosion resistance and recycling metals Life cycle assessment Reversible reactions and dynamic equilibrium The Haber process and its conditions

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 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

Groups in the Periodic Table

The pattern in alkali metal reactivity and why it happens

3 things to know
Paper 4

Overview

The order of lithium, sodium and potassium, predictions for rubidium and caesium, and why reactivity rises down group 1 through atom size, shielding and the loss of the outer electron.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Explain, in terms of the outer electron, why reactivity increases down group 1 and why lithium is less reactive than sodium.

Key term

Place lithium, sodium and potassium in order of their reactivity with water, starting with the least reactive.

Key term

How does reactivity with water change going down group 1?

Questions from this subtopic

Each one with the model answer underneath.

1
Place lithium, sodium and potassium in order of their reactivity with water, starting with the least reactive.
Model answer
Lithium is the least reactive, then sodium, and potassium is the most reactive.
2
How does reactivity with water change going down group 1?
Model answer
Reactivity increases going down group 1.
3
Which takes longer to disappear on water, a piece of lithium or an identical piece of potassium?
Model answer
The lithium takes longer, because lithium is the less reactive of the two metals.
4
Why is potassium the only one of lithium, sodium and potassium whose hydrogen normally catches fire on water?
Model answer
Potassium reacts fastest and releases heat quickly enough to set the hydrogen alight.
5
Rubidium lies below potassium in group 1. Predict how it behaves when dropped into water.
Model answer
Rubidium reacts even more violently than potassium, because reactivity increases further down the group.
6
Caesium lies below rubidium in group 1. Predict how vigorous its reaction with water is.
Model answer
Caesium reacts more violently still, and the reaction is explosive.

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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.

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