How does the melting point of a typical polymer compare with that of a clay ceramic?

A polymer softens or melts at a few hundred degrees Celsius, while a ceramic withstands well over a thousand.

Compare the electrical conductivity of a metal with that of a polymer.

A metal conducts extremely well, while a polymer is an insulator that conducts many times less.

Compare the strength of glass in compression with its strength in tension.

Glass is far stronger in compression than in tension, which is why it cracks when it is bent.

Which is stronger for its mass, a carbon fibre composite or steel?

The composite, because it has a comparable strength but a much lower density.

OCR GCSE Chemistry A J248

Chemical Reactions

Topic overview Writing formulae of elements and compounds Balanced equations, and deducing formulae from ions Ionic equations, and state symbols The mole and the Avogadro constant Conservation of mass, and changes of mass in open systems Stoichiometry, and calculating reacting masses Exothermic and endothermic reactions, and reaction profiles Activation energy, and bond energy calculations Oxidation and reduction, by oxygen and by electrons Acids, alkalis and neutralisation The ionic equation for neutralisation, and reactions of acids Dilute and concentrated, weak and strong The pH scale, and hydrogen ion concentration pH as a factor of ten, and measuring pH Products at the electrodes, and molten ionic compounds Electrolysis of aqueous solutions Inert and non-inert electrodes

Elements, Compounds and Mixtures

Topic overview Purity, and melting point data Relative formula mass and empirical formulae Formulations, and separating mixtures Paper and thin layer chromatography Interpreting chromatograms and Rf values Choosing a purification method Metals and non-metals in the Periodic Table Electron arrangement and position in the Periodic Table Ionic, covalent and metallic bonding compared Dot and cross diagrams, and the limits of models Reactions, electron arrangement and Mendeleev's table Carbon's four bonds, and the variety of organic compounds Diamond, graphite, fullerenes and graphene Bond strength, intermolecular forces and predicting state Bulk properties of ionic, molecular and giant structures Nanoparticles: size and surface area to volume Uses and risks of nanoparticulate materials

Global Challenges

Topic overview Extracting metals by reduction and by electrolysis Biological methods of metal extraction Rate against yield in industry, and reaction conditions The Haber process and fertiliser production Nitrogen, phosphorus and potassium in agriculture Life cycle assessment Recycling, and the decisions behind it Alloys, and the corrosion of metals Comparing glass, ceramics, polymers, composites and metals Functional groups and homologous series Predicting the products of organic reactions Addition polymerisation Condensation polymerisation, and making a polymer DNA and other natural polymers Fractional distillation of crude oil The fractions, and crude oil as a feedstock Dependence on hydrocarbons, and cracking Chemical cells and fuel cells The Earth's early atmosphere, and how oxygen developed The greenhouse effect, and evidence for climate change Effects of carbon dioxide and methane, and air pollutants Producing potable water

Monitoring and Controlling Chemical Reactions

Topic overview Concentration in mol/dm³, and titration Titration calculations, and the mass of a solute Molar gas volume and the volumes of gases Theoretical mass and percentage yield Atom economy, and choosing a reaction pathway Measuring the rate of a reaction, and rate graphs Factors affecting rate, and collision theory Surface area and rate Catalysts and how they work Reversible reactions and dynamic equilibrium Changing the conditions of an equilibrium Activation energy, and enzymes as catalysts

Particles

Topic overview The particle model and changes of state Limitations of the particle model How the atomic model changed, and the structure of the atom The size of atoms, and the subatomic particles Calculating protons, neutrons and electrons

Predicting and Identifying Reactions

Topic overview Groups 1, 7 and 0, and why they behave as they do Transition metals Predicting reactivity from the Periodic Table Reactivity of metals with water and acids Tests for oxygen, hydrogen, carbon dioxide and chlorine Tests for aqueous cations and anions Flame tests, and identifying metal ions Identifying a species from test results Instrumental methods of analysis

Global Challenges

Comparing glass, ceramics, polymers, composites and metals

2 things to know
Paper 4

Overview

How metals, ceramics, polymers, glass and composites compare in toughness, density, melting point, conductivity and strength, what a composite is, and choosing materials for windows, furnaces, bicycles, cables, kettles and bridges.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Which stands up better to a sharp blow, a metal or a clay ceramic, and why?

Key term

Compare the density of aluminium with the density of steel.

Questions from this subtopic

Each one with the model answer underneath.

1
Which stands up better to a sharp blow, a metal or a clay ceramic, and why?
Model answer
The metal, because it bends or dents, while a ceramic is brittle and shatters.
2
Compare the density of aluminium with the density of steel.
Model answer
Aluminium is roughly a third as dense as steel.
3
How does the melting point of a typical polymer compare with that of a clay ceramic?
Model answer
A polymer softens or melts at a few hundred degrees Celsius, while a ceramic withstands well over a thousand.
4
Compare the electrical conductivity of a metal with that of a polymer.
Model answer
A metal conducts extremely well, while a polymer is an insulator that conducts many times less.
5
Compare the strength of glass in compression with its strength in tension.
Model answer
Glass is far stronger in compression than in tension, which is why it cracks when it is bent.
6
Which is stronger for its mass, a carbon fibre composite or steel?
Model answer
The composite, because it has a comparable strength but a much lower density.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book

2Open book

3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Chemical Reactions

Elements, Compounds and Mixtures

Global Challenges

Monitoring and Controlling Chemical Reactions

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Values 7.

belowaboveat

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AThe products sit at a higher energy level than the reactants.

BThe activation energy, the energy that must be supplied before the reaction can happen.

CThe reactants, the products, the activation energy and the overall energy change.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Sodium ions give a bright yellow flame colour.

TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Global Challenges, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a month See how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.