What information about a substance do you need in order to predict its state at a given temperature?

Its melting point and its boiling point.

Explain why an ionic compound melts at a far higher temperature than a substance made of small molecules.

Melting an ionic solid needs enough energy to overcome strong electrostatic forces throughout the lattice, while a molecular solid needs only enough to overcome weak forces between whole molecules.

Explain, in terms of energy, why more energy is needed to boil water than to melt the same mass of ice.

Boiling has to separate the molecules completely by overcoming all the forces between them, while melting only lets them move past one another.

AQA GCSE Combined Science Chemistry 8464

Atomic Structure and the Periodic Table

Topic overview Atoms, elements and compounds Word equations, symbols and balanced equations Mixtures From the plum pudding model to the nuclear model Bohr, Chadwick and the modern model of the atom Relative electrical charges of subatomic particles Size and mass of atoms Relative atomic mass and electronic structure The periodic table Development of the periodic table Metals and non-metals Group 0 Group 1 Group 7

Bonding, Structure, and the Properties of Matter

Topic overview Chemical bonds, including metallic bonding Ionic bonding Ionic compounds Covalent bonding and how it is represented The three states of matter and changes of state Predicting state, state symbols, and the limits of the particle model Properties of ionic compounds Properties of small molecules Polymers and giant covalent structures Properties of metals and alloys, and why metals conduct Diamond and graphite Graphene and fullerenes

Chemical Analysis

Topic overview Pure substances Formulations Chromatography Tests for hydrogen, oxygen, carbon dioxide and chlorine

Chemical Changes

Topic overview The reactivity series Metal oxides, extraction, and redox in terms of electrons Acids reacting with metals, neutralisation and salts Soluble salts The pH scale and neutralisation Strong and weak acids The process of electrolysis, and molten ionic compounds Using electrolysis to extract metals Electrolysis of aqueous solutions Representation of reactions at electrodes as half equations

Chemistry of the Atmosphere

Topic overview The Earth's early atmosphere How oxygen increased and carbon dioxide decreased The gases in today's atmosphere, and which are greenhouse gases Human activities which contribute to an increase in greenhouse gases in the atmosphere Global climate change and carbon footprints Atmospheric pollutants from fuels, and their effects

Energy Changes

Topic overview Exothermic and endothermic reactions Everyday uses, and investigating temperature change Reaction profiles The energy change of reactions

Organic Chemistry

Topic overview Crude oil, hydrocarbons and alkanes Fractional distillation and petrochemicals Properties of hydrocarbons Cracking, and testing alkenes with bromine water Why cracking is useful, and equations for it

Quantitative Chemistry

Topic overview Conservation of mass and balanced chemical equations Relative formula mass and concentration of solutions Mass changes when a gas is involved, and measurement uncertainty Moles Amounts of substances in equations, and balancing using moles Limiting reactants

The Rate and Extent of Chemical Change

Topic overview Measuring the mean rate of a reaction Rate from graphs, and the gradient of a tangent Factors which affect the rates of chemical reactions Collision theory and activation energy Catalysts Reversible reactions and dynamic equilibrium The effect of changing conditions on equilibrium The effect of changing concentration The effect of temperature changes on equilibrium The effect of pressure changes on equilibrium

Using Resources

Topic overview Using the Earth's resources and sustainable development Producing potable water in the UK Desalination, and analysing water samples Waste water treatment Alternative methods of extracting metals Life cycle assessment Ways of reducing the use of resources

Bonding, Structure, and the Properties of Matter

Predicting state, state symbols, and the limits of the particle model

3 things to know
Chemistry Paper 1

Overview

Predicting state from melting and boiling points, why ionic solids melt far above molecular ones, why boiling takes more energy than melting, the limits of the particle model, and the four state symbols.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

A substance melts at −7 °C and boils at 59 °C. What is its state at 25 °C?

Numbers

A substance has a melting point of 801 °C and a boiling point of 1413 °C. State and explain its state at 1000 °C.

Key term

Why is it wrong to describe a single copper atom as shiny and malleable?

Questions from this subtopic

Each one with the model answer underneath.

1
What information about a substance do you need in order to predict its state at a given temperature?
Model answer
Its melting point and its boiling point.
2
A substance melts at −7 °C and boils at 59 °C. What is its state at 25 °C?
Model answer
Liquid, because 25 °C is above its melting point but below its boiling point.
3
A substance has a melting point of 801 °C and a boiling point of 1413 °C. State and explain its state at 1000 °C.
Model answer
Liquid, because 1000 °C lies between its melting point and its boiling point.
4
Explain why an ionic compound melts at a far higher temperature than a substance made of small molecules.
Model answer
Melting an ionic solid needs enough energy to overcome strong electrostatic forces throughout the lattice, while a molecular solid needs only enough to overcome weak forces between whole molecules.
5
Explain, in terms of energy, why more energy is needed to boil water than to melt the same mass of ice.
Model answer
Boiling has to separate the molecules completely by overcoming all the forces between them, while melting only lets them move past one another.
6
Why is it wrong to describe a single copper atom as shiny and malleable?
Model answer
Shine and malleability are bulk properties of the whole giant structure, not properties an individual atom has.

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Atomic Structure and the Periodic Table

Bonding, Structure, and the Properties of Matter

Chemical Analysis

Chemical Changes

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AMolecular size controls boiling point, viscosity and flammability.

BSmall molecules make gases and petrol that ignite easily.

CLarge molecules make thick liquids burned in furnaces and ships.

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Base means any substance that neutralises an acid.

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