Describe the structure of diamond.

It is a giant covalent structure in which every carbon atom is bonded to four others by strong covalent bonds in a rigid three-dimensional lattice.

Describe the structure of graphite.

It is a giant covalent structure in which each carbon atom bonds to three others, forming flat layers of hexagonal rings held to each other only by weak forces.

Explain why graphite conducts electricity.

Because each carbon atom uses only three of its outer electrons in bonding, leaving one delocalised electron free to move along the layers.

OCR GCSE Combined Science Chemistry J250

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

Global Challenges

Topic overview Extracting metals by reduction and by electrolysis Biological methods of metal extraction Life cycle assessment Recycling, and the decisions behind it Fractional distillation of crude oil The fractions, and crude oil as a feedstock Dependence on hydrocarbons, and cracking 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 Mass of solute, concentration and dilution calculations 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 Predicting reactivity from the Periodic Table Reactivity of metals with water and acids Tests for oxygen, hydrogen, carbon dioxide and chlorine

Elements, Compounds and Mixtures

Diamond, graphite, fullerenes and graphene

3 things to know
Paper 9 (Chemistry)

Overview

The structures of diamond and graphite, why diamond is hard and does not conduct while graphite is soft, slippery and conducting, what graphene is and why it is strong, light and conducting, what a fullerene is, buckminsterfullerene C₆₀, and why fullerenes melt at far lower temperatures than diamond.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Explain why diamond is extremely hard and has a very high melting point.

Key term

Explain why diamond does not conduct electricity.

Key term

Explain why graphite is soft and slippery.

Questions from this subtopic

Each one with the model answer underneath.

1
Describe the structure of diamond.
Model answer
It is a giant covalent structure in which every carbon atom is bonded to four others by strong covalent bonds in a rigid three-dimensional lattice.
2
Explain why diamond is extremely hard and has a very high melting point.
Model answer
Because a great many strong covalent bonds run throughout the structure and a large amount of energy is needed to break them.
3
Explain why diamond does not conduct electricity.
Model answer
Because all four outer electrons on each carbon atom are used in bonding, leaving no delocalised electrons or ions free to move.
4
Describe the structure of graphite.
Model answer
It is a giant covalent structure in which each carbon atom bonds to three others, forming flat layers of hexagonal rings held to each other only by weak forces.
5
Explain why graphite is soft and slippery.
Model answer
Because the forces between its layers are weak, so the layers can slide over one another easily.
6
Explain why graphite conducts electricity.
Model answer
Because each carbon atom uses only three of its outer electrons in bonding, leaving one delocalised electron free to move along the layers.

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Chemical Reactions

Elements, Compounds and Mixtures

Global Challenges

Monitoring and Controlling Chemical Reactions

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