OCR GCSE SCIENCES B (21st Century Science)

ALL MY GCSE CHEMISTRY REVISION NOTES

BEWARE - this page is for Y10 2016-2017 onwards only!

OCR Level 1/2 GCSE (9–1) in Chemistry B (Twenty First Century Science) (J258)

and OCR Level 1/2 GCSE (9–1) in Combined Science B Chemistry (Twenty First Century Science) (J260)

OCR (9-1) 21st Century GCSE CHEMISTRY B Chapters C1, C2 and C3

'Old' OCR 21st Century GCSE sciences for Y11 finishing 2016-2017

INDEX for all links

These topic revision summaries below for the NEW GCSE sciences are all unofficial but based on the NEW 2016 official syllabus-specifications for Y10 students from September 2016 onwards

(HT only) means higher tier only (NOT FT) and (GCSE chemistry only) means for the separate science, NOT for Combined Science chemistry

Links to specific GCSE chemistry notes about the topic in question have been added, and from these pages, you may find other links to more useful material linked to the topic.


Be aware that both Paper 1 and Paper 2 assess content from ALL chapters !!!

What's assessed in these papers?

SUMMARY Chapter C1: Air and water   (this page)

Revision summary Chapter C1.1 How has the Earth’s atmosphere changed over time, and why?

Revision summary Chapter C1.2 Why are there temperatures changes in chemical reactions?

Revision summary Chapter C1.3 What is the evidence for climate change, why is it occurring?

Revision summary Chapter C1.4 How can scientists help improve the supply of potable water?

SUMMARY Chapter C2: Chemical patterns  (this page)

Revision summary Chapter C2.1 How have our ideas about atoms developed over time?

Revision summary Chapter C2.2 What does the Periodic Table tell us about the elements?

Revision summary Chapter C2.3 How do metals and non-metals combine to form compounds?

Revision summary Chapter C2.4 How are equations used to represent chemical reactions?

Revision summary Chapter C2.5 What are the properties of transition metals?  (GCSE Chemistry only)

SUMMARY Chapter C3: Chemicals of the natural environment   (this page)

Revision summary Chapter C3.1 How are the atoms held together in a metal?

Revision summary Chapter C3.2 How are metals with different reactivities extracted?

Revision summary Chapter C3.3 What are electrolytes and what happens during electrolysis?

Revision summary Chapter C3.4 Why is crude oil important as a source of new materials?

SUMMARY Chapter C4: Material choices    (separate page)

Chapter C4.1 How is data used to choose a material for a particular use?

Chapter C4.2 What are the different types of polymers?  (GCSE Chemistry only)

Chapter C4.3/4.2 How do bonding and structure affect properties of materials?

Chapter C4.4/4.3 Why are nanoparticles so useful?

Chapter C4.5/4.4 What happens to products at the end of their useful life?

SUMMARY Chapter C5: Chemical analysis   (separate page)

Chapter C5.1 How are chemicals separated and tested for purity?

Chapter C5.2 How do chemists find the composition of unknown samples?  (GCSE Chemistry only)

Chapter C5.3/5.2 How are the amounts of substances in reactions calculated?

Chapter C5.4/5.3 How are the amounts of chemicals in solution measured?

SUMMARY Chapter C6: Making useful chemicals   (separate page)

Chapter C6.1 What useful products can be made from acids?

Chapter C6.2 How do chemists control the rate of reactions?

Chapter C6.3 What factors affect the yield of chemical reactions?

Chapter C6.4 How are chemicals made on an industrial scale?  (GCSE Chemistry only)

SUMMARY Chapter C7: Ideas about Science   (separate page)

IaS1 What needs to be considered when investigating a phenomenon scientifically?

IaS2 What conclusions can we make from data?

IaS3 How are scientific explanations developed?

IaS4 How do science and technology impact society?


Chapter C1: Air and water


Chapter C1.1 How has the Earth’s atmosphere changed over time, and why?

The Earth, its atmosphere and its oceans are made up from elements and compounds in different states. The particle can be used to describe the states of these substances and what happens to the particles when they change state. The particle model can be represented in different ways, but these are limited because they do not accurately represent the scale or behaviour of actual particles, they assume that particles are inelastic spheres, and they do not fully take into account the different interactions between particles.

The formation of our early atmosphere and oceans, and the state changes involved in the water cycle, can be described using the particle model.

Explanations about how the atmosphere was formed and has changed over time are based on evidence, including the types and chemical composition of ancient rocks, and fossil evidence of early life.

Explanations include ideas about early volcanic activity followed by cooling of the Earth resulting in formation of the oceans. The evolution of photosynthesising organisms, formation of sedimentary rocks, oil and gas, and the evolution of animals led to changes in the amounts of carbon dioxide and oxygen in the atmosphere.

1. Be able to recall and explain the main features of the particle model in terms of the states of matter and change of state, distinguishing between physical and chemical changes and recognise that the particles themselves do not have the same properties as the bulk substances.

Practical work:

measure temperature against time and plot a cooling curve for stearic acid or heating curve for ice

using the particle model to explain state changes

2. (HT only) Be able to explain the limitations of the particle model in relation to changes of state when particles are represented by inelastic spheres.

3. Be able to use ideas about energy transfers and the relative strength of forces between particles to explain the different temperatures at which changes of state occur.

4. Be able to use data to predict states of substances under given conditions.

States of Matter - particle theory - gas, liquid & solid properties-behaviour, state changes

Multiple choice quiz on States of Matter (gases, liquids & solids) and State Changes

5. Be able to interpret evidence for how it is thought the atmosphere was originally formed.

6. Be able to describe how it is thought an oxygen-rich atmosphere developed over time.

Be able to distinguish data from explanatory ideas in accounts of how the atmosphere was formed

Past ancient atmospheres, changes due to man's activities

Evolution of atmosphere - changes over billions of years, origin of life

Our modern lifestyle has created a high demand for energy. Combustion of fossil fuels for transport and energy generation leads to emissions of pollutants. Carbon monoxide, sulfur dioxide, nitrogen oxides and particulates directly harm human health. Some pollutants cause indirect problems to humans and the environment by the formation of acid rain and smog. Scientists monitor the concentration of these pollutants in the atmosphere and strive to develop approaches to maintaining air quality.

The combustion reactions of fuels and the formation of pollutants can be represented using word and symbol equations. The formulae involved in these reactions can be represented by models, diagrams or written formulae. The equations should be balanced. When a substance chemically combines with oxygen it is an example of oxidation. Combustion reactions are therefore oxidation. Some gases involved in combustion reactions can be identified by their chemical reactions.

7. Be able to describe the major sources of carbon monoxide and particulates (incomplete combustion), sulfur dioxide (combustion of sulfur impurities in fuels), oxides of nitrogen (oxidation of nitrogen at high temperatures and further oxidation in the air)

unintended impacts of burning fossil fuels on air quality

catalytic converters, low sulfur petrol and gas scrubbers as positive applications of science

8. Be able to explain the problems caused by increased amounts of these substances and describe approaches to decreasing the emissions of these substances into the atmosphere including the use of catalytic converters, low sulfur petrol and gas scrubbers to decrease emissions.

Alkanes - saturated hydrocarbons, reactions including combustion

Air pollution - sulfur oxides, nitrogen oxides, acid rain

Air pollution - incomplete combustion, carbon monoxide & soot

9. Be able to use chemical symbols to write the formulae of elements and simple covalent compounds.

10. Be able to use the names and symbols of common elements and compounds and the principle of conservation of mass to write formulae and balanced chemical equations.

Law of Conservation of Mass and simple reacting mass calculations

11. Be able to use arithmetic computations and ratios when balancing equations.

How to write word & balance symbol equations

Balancing symbol equations worksheet - reactions of acids & bases and symbol equation answers

Multiple Choice Quiz on balancing Symbol Chemical Equations with numbers

Number fill Quiz on completing symbol equations (Q1 Q2 Q3)

12. Be able to describe tests to identify oxygen, hydrogen and carbon dioxide.

Summary of tests for gases and ions

13. Be able to explain oxidation in terms of gain of oxygen.

Introduction to oxidation and reduction


Chapter C1.2 Why are there temperature changes in chemical reactions?

When a fuel is burned in oxygen the surroundings are warmed; this is an example of an exothermic reaction. There are also chemical reactions that cool their surroundings; these are endothermic reactions. Energy has to be supplied before a fuel burns. For all reactions, there is a certain minimum energy needed to break bonds so that the reaction can begin. This is the activation energy. The activation energy, and the amount of energy associated with the reactants and products, can be represented using a reaction profile. Atoms are rearranged in chemical reactions. This means that bonds between the atoms must be broken and then reformed. Breaking bonds requires energy (the activation energy) whilst making bonds gives out energy.

(HT only) Energy changes in a reaction can be calculated if we know the bond energies involved in the reaction.

1. Be able to distinguish between endothermic and exothermic reactions on the basis of the temperature change of the surroundings.

Practical work: investigate different chemical reactions to find out if they are exothermic or endothermic

2. Be able to draw and label a reaction profile for an exothermic and an endothermic reaction, identifying activation energy.

3. Be able to explain activation energy as the energy needed for a reaction to occur.

4. Be able to interpret charts and graphs when dealing with reaction profiles.

5. (HT only) Be able to calculate energy changes in a chemical reaction by considering bond breaking and bond making energies

6. Be able to carry out arithmetic computations when calculating energy changes.

7. (GCSE Chemistry only) Be able to describe how you would investigate a chemical reaction to determine whether it is endothermic or exothermic.

Heat changes in chemical/physical changes - exothermic and endothermic

Calorimeter methods of determining energy changes and examples of experiments you can do

Reversible reactions and energy changes

Activation energy and reaction profiles

Introduction to bond energy/enthalpy calculations

Energy transfer calculations from calorimeter results

Harder multiple choice quiz on Energy Changes in Chemical Reactions

(GCSE Chemistry only) Using hydrogen fuel cells as an alternative to fossil fuels for transport is one way to decrease the emission of pollutants in cities. The reaction in the fuel cell is equivalent to the combustion of hydrogen and gives the same product (water) but the energy drives an electric motor rather than an internal combustion engine. However, hydrogen is usually produced by electrolysis, which may use electricity generated from fossil fuels so pollutants may be produced elsewhere. There are difficulties in storing gaseous fuel for fuel cells which limits their practical value for use in cars.

8. (GCSE Chemistry only) Be able to recall that a chemical cell produces a potential difference until the reactants are used up Ideas about Science: fuel cells as a positive application of science to mitigate the effects of emissions.

9. (GCSE Chemistry only) Be able to evaluate the advantages and disadvantages of hydrogen/oxygen and other fuel cells for given uses.

Simple cells (batteries)

Fuel Cells e.g. the hydrogen - oxygen fuel cell


Chapter C1.3 What is the evidence for climate change, why is it occurring?

Some electromagnetic radiation from the Sun passes through the atmosphere and is absorbed by the Earth warming it. The warm Earth emits infrared radiation which some gases, including carbon dioxide and methane, absorb and re-emit in all directions; this keeps the Earth warmer than it would otherwise be and is called the greenhouse effect. Without the greenhouse effect the Earth would be too cold to support life. The proportion of greenhouse gases in the Earth’s atmosphere has increased over the last 200 years as a result of human activities. There are correlations between changes in the composition of the atmosphere, consumption of fossil fuels and global temperatures over time. Although there are uncertainties in the data, most scientists now accept that recent climate change can be explained by increased greenhouse gas emissions. Patterns in the data have been used to propose models to predict future climate changes. As more data is collected, the uncertainties in the data decrease, and our confidence in models and their predictions increases. Scientists aim to reduce emissions of greenhouse gases, for example by reducing fossil fuel use and removing gases from the atmosphere by carbon capture and reforestation. These actions need to be supported by public regulation. Even so, it is difficult to mitigate the effect of emissions due to the very large scales involved. Each new measure may have unforeseen impacts on the environment, making it difficult to make reasoned judgments about benefits and risks.

1. Be able to describe the greenhouse effect in terms of the interaction of radiation with matter.

What is global warning and what is the evidence for it?

Practical work:

Investigating climate change models – both physical models and computer models.

Using ideas about correlation and cause, about models and the way science explanations are developed when discussing climate change

Considering risks, costs and benefits of fuel use and its sustainability and effects on climate.

2. Be able to evaluate the evidence for additional anthropogenic causes of climate change, including the correlation between change in atmospheric carbon dioxide concentration and the consumption of fossil fuels, and describe the uncertainties in the evidence base

3. Be able to describe the potential effects of increased levels of carbon dioxide and methane on the Earth’s climate, including where crops can be grown, extreme weather patterns, melting of polar ice and flooding of low land

4. Be able to describe how the effects of increased levels of carbon dioxide and methane may be mitigated, including consideration of scale, risk and environmental implications

5. Be able to extract and interpret information from charts, graphs and tables.

6. Be able to use orders of magnitude to evaluate the significance of data

making it difficult to make reasoned judgments about benefits and risks

public regulation of targets for emissions and reasons why different decisions on issues related to climate change might be made in view of differences in personal, social, or economic context

Greenhouse effect, global warming, climate change, carbon footprint from fossil fuel burning


Chapter C1.4 How can scientists help improve the supply of potable water?

The increase in global population means there is a greater need for potable water. Obtaining potable water depends on the availability of waste, ground or salt water and treatment methods. Chlorine is used to kill microorganisms in water. The benefits of adding chlorine to water to stop the spread of waterborne diseases outweigh risks of toxicity. In some countries the chlorination of water is subject to public regulation, but other parts of the world are still without chlorinated water and this leads to a higher risk of disease.

1. Be able to describe the principal methods for increasing the availability of potable water, in terms of the separation techniques used, including the ease of treating waste, ground and salt water including filtration and membrane filtration; aeration, use of bacteria; chlorination and distillation (for salt water).

technologies to increase the availability of potable water can make a positive difference to people’s lives

access to treated water raises issues about risk, cost and benefit and providing treated water for all raises ethical issues

Practical work: Identify unknown gases

2. Be able to describe a test to identify chlorine (using blue litmus paper).

Water cycle, potable water, water treatment, pollution, tests for ions in water

Summary of tests for gases and ions


Chapter C2: Chemical patterns


Chapter C2.1 How have our ideas about atoms developed over time?

The modern model of the atom developed over time. Stages in the development of the model included ideas by the ancient Greeks (4 element ideas), Dalton (first particle model), Thomson (‘plum pudding’ model), Rutherford (idea of atomic nucleus) and Bohr (shells of electrons). Models were rejected, modified and extended as new evidence became available. The development of the atomic model involved scientists suggesting explanations, making and checking predictions based on their explanations, and building on each other’s work (IaS3). The Periodic Table can be used to find the atomic number and relative atomic mass of an atom of an element, and then work out the numbers of protons, neutrons and electrons. The number of electrons in each shell can be represented by simple conventions such as dots in circles or as a set of numbers (for example, sodium as 2.8.1). Atoms are small – about 10-10 m across, and the nucleus is at the centre, about a hundred-thousandth of the diameter of the atom. Molecules are larger, containing from two to hundreds of atoms. Objects that can be seen with the naked eye contain millions of atoms.

1. Be able to describe how and why the atomic model has changed over time to include the main ideas of Dalton, Thomson, Rutherford and Bohr

Understanding how scientific explanations and models develop in the context of changing ideas about the atomic model.

2. Be able to describe the atom as a positively charged nucleus surrounded by negatively charged electrons, with the nuclear radius much smaller than that of the atom and with most of the mass in the nucleus.

3. Be able to recall relative charges and approximate relative masses of protons, neutrons and electrons.

4. Be able to estimate the size and scale of atoms relative to other particles.

5. Be able to recall the typical size (order of magnitude) of atoms and small molecules.

6. Be able to relate size and scale of atoms to objects in the physical world.

7. Be able to calculate numbers of protons, neutrons and electrons in atoms, given atomic number and mass number of isotopes or by extracting data from the Periodic Table.

Atomic Structure - nucleus, electrons, isotopes etc.

Multiple choice quiz on  Atomic structure, isotopes & electronic structure of atoms

Atomic Structure crossword puzzle * Answers

Gap-fill worksheet on Atomic Structure

Matching pair quiz on Atomic and electronic structure 1. fundamental particles

Matching pair quiz on Atomic and electronic structure 2. periodic table


Chapter C2.2 What does the Periodic Table tell us about the elements?

Elements in the modern Periodic Table are arranged in periods and groups, based on their atomic numbers. Elements in the same group have the same number of electrons in their outer shells. The number of electron shells increases down a group but stays the same across a period.

Mendeleev proposed the first arrangement of elements in the Periodic Table. Although he did not know about atomic structure, he reversed the order of some elements with respect to their masses, left gaps for undiscovered elements and predicted their properties. His ideas were accepted because when certain elements were discovered they fitted his gaps and the development of a model for atomic structure supported his arrangement. The later determination of the number of protons in atoms provided an explanation for the order he proposed.

The Periodic Table shows repeating patterns in the properties of the elements. Metals and non-metals can be identified by their position in the Periodic Table and by comparing their properties (physical properties including electrical conductivity).

Properties of elements within a group show trends. The reactivity of Group 1 metals elements increases down the group, shown by their reactivity with moist air, water and chlorine.

The Group 7 halogens are non-metals and become less reactive down the group. This is shown in reactions such as their displacement reactions with compounds of other halogens in the group.

1. Be able to explain how the position of an element in the Periodic Table is related to the arrangement of electrons in its atoms and hence to its atomic number.

Practical work:

reactions of Group 1 (demonstration) and Group 7 (for example displacement)

understanding how scientific explanations and models develop, in the context of the Periodic Table

2. Be able to describe how Mendeleev organised the elements based on their properties and relative atomic masses.

3. Be able to describe how discovery of new elements and the ordering elements by atomic number supports Mendeleev’s decisions to leave gaps and reorder some elements.

4. Be able to describe metals and non-metals and explain the differences between them on the basis of their characteristic physical and chemical properties, including melting point, boiling point, state and appearance, density, formulae of compounds and relative reactivity and electrical conductivity.

Periodic Table Notes - an overview, groups, periods, metals & non-metals

5. Be able to recall the simple properties of Group 1 elements including their reaction with moist air, water, and chlorine.

Making and testing predictions about trends and patterns in the Periodic Table

6. Be able to recall the simple properties of Group 7 elements including their states and colours at room temperature and pressure, their colours as gases, their reactions with Group 1 elements and their displacement reactions with other metal halides.

displacement reactions with compounds of other halogens in the group

7. Be able to predict possible reactions and probable reactivity of elements from their positions in the Periodic Table.

Making and testing predictions about trends and patterns in the Periodic Table

8. Be able to describe experiments to identify the reactivity pattern of Group 7 elements including displacement reactions.

9. Be able to describe experiments to identify the reactivity pattern of Group 1 elements.

Group 1 Alkali Metals

Multiple choice quiz on the Group 1 Alkali Metals

Word-fill worksheet on the Group 1 Alkali Metals

Group 7 Halogens - physical and chemical properties

Multiple choice quiz on the Group 7 Halogens

A Group 7 "Halogens" task sheet worksheet * (answers)

Word-fill work sheet on the Halogens

The Halogens (matching pair quiz on their appearance)


Chapter C2.3 How do metals and non-metals combine to form compounds?

Group 0 contains elements with a full outer shell of electrons. This arrangement is linked to their inert, unreactive properties. They exist as single atoms and hence are gases with low melting and boiling points. Group 1 elements combine with Group 7 elements by ionic bonding. This involves a transfer of electrons leading to charged ions.

Atoms and ions can be represented using dot and cross diagrams as simple models. Metals, such as Group 1 metals, lose electrons from the outer shell of their atoms to form ions with complete outer shells and with a positive charge. Non-metals, such as Group 7, form ions with a negative charge by gaining electrons to fill their outer shell. The number of electrons lost or gained determines the charge on the ion.

The properties of ionic compounds such as Group 1 halides can be explained in terms of the ionic bonding. Positive ions and negative ions are strongly attracted together and form giant lattices. Ionic compounds have high melting points in comparison to many other substances due to the strong attraction between ions which means a large amount of energy is needed to break the attraction between the ions. They dissolve in water because their charges allow them to interact with water molecules. They conduct electricity when molten or in solution because the charged ions can move, but not when solid because the ions are held in fixed positions.

Practical work:

test the properties of ionic compounds

dot and cross diagrams as models of atoms and ions ,and the limitations of these models

2-D and 3-D representations as simple models of the arrangement of ions, and the limitations of these models

1. Be able to recall the simple properties of Group 0 including their low melting and boiling points, their state at room temperature and pressure and their lack of chemical reactivity.

Group 0 Noble Gases

Multiple choice quiz on Group 0 The Noble Gases

Wordfill worksheet on the Noble Gases (answers)

2. Be able to explain how observed simple properties of Groups 1, 7 and 0 depend on the outer shell of electrons of the atoms and predict properties from given trends down the groups.

Group 1 Alkali Metals

Group 7 Halogens - physical and chemical properties

3. Be able to explain how the reactions of elements are related to the arrangement of electrons in their atoms and hence to their atomic number.

4. Be able to explain how the atomic structure of metals and non-metals relates to their position in the Periodic Table.

Periodic Table Notes - an overview, groups, periods, metals & non-metals

5. Be able to describe the nature and arrangement of chemical bonds in ionic compounds.

6. Be able to explain ionic bonding in terms of electrostatic forces and transfer of electrons

7. Be able to calculate numbers of protons, neutrons and electrons in atoms and ions, given atomic number and mass number or by using the Periodic Table.

8. Be able to construct dot and cross diagrams for simple ionic substances

9. Be able to explain how the bulk properties of ionic materials are related to the type of bonds they contain.

10. Be able to use ideas about energy transfers and the relative strength of attraction between ions to explain the melting points of ionic compounds compared to substances with other types of bonding.

The arrangement of ions can be represented in both 2-D and 3-D. These representations are simple models which have limitations, for example they do not fully show the nature or movement of the electrons or ions, the interaction between the ions, their arrangement in space, their relative sizes or scale.

11. Be able to describe the limitations of particular representations and models of ions and ionically bonded compounds, including dot and cross diagrams, and 3-D representations

12. Be able to translate information between diagrammatic and numerical forms and represent three dimensional shapes in two dimensions and vice versa when looking at chemical structures for ionic compounds.

Introduction to Chemical Bonding

Ionic bonding and ionic compounds and their properties


Chapter C2.4 How are equations used to represent chemical reactions?

The reactions of Group 1 and Group 7 elements can be represented using word equations and balanced symbol equations with state symbols. The formulae of ionic compounds, including Group 1 and Group 7 compounds can be worked out from the charges on their ions. Balanced equations for reactions can be constructed using the formulae of the substances involved, including hydrogen, water, halogens (chlorine, bromine and iodine) and the hydroxides, chlorides, bromides and iodides (halides) of Group 1 metals.

1. Be able to use chemical symbols to write the formulae of elements and simple covalent and ionic compounds.

2. Be able to use the formulae of common ions to deduce the formula of Group 1 and Group 7 compounds.

3. Be able to use the names and symbols of the first 20 elements, Groups 1, 7 and 0 and other common elements from a supplied Periodic Table to write formulae and balanced chemical equations where appropriate.

4. Be able to describe the physical states of products and reactants using state symbols (s, l, g and aq).

How to write word & balance symbol equations, work out formula and name compounds


Chapter C2.5 What are the properties of the transition metals? (GCSE Chemistry only)

The transition metals do not show group properties like the elements in Group 1 and Group 7; they form a family of elements with general properties that are different from those of other metals. These properties make the transition metals particularly useful. They all have relatively high melting points and densities. Transitions metals are generally less reactive than Group 1 metals, and some are very unreactive (for example silver and gold). Some transition metal elements and their compounds are used widely in the manufacture of consumer goods and as catalysts in industry, both of which represent beneficial applications of science.

1. Be able to recall the general properties of transition metals (melting point, density, reactivity, formation of coloured ions with different charges and uses as catalysts) and exemplify these by reference to copper, iron, chromium, silver and gold.

Practical work: Investigating colours of transition metal compounds, and their effectiveness as catalysts

The Transition Metals eg iron and copper - their physical/chemical properties & uses

Multiple choice quiz on the Transition Metals and their Compounds

Word-fill worksheet on the Transition Metals


Chapter C3: Chemicals of the natural environment


Chapter C3.1 How are the atoms held together in a metal?

Chemists use a model of metal structure to explain the properties of metals (IaS3). In the model, metal atoms are arranged closely together in a giant structure, held together by attraction between the positively charged atoms and a ‘sea’ of negatively charged electrons. Metals are malleable and ductile because the ions can slide over each other but still be held together by the electrons; they conduct electricity and heat because their electrons are free to move; and they have high boiling points and melting points due to the strong electrostatic attraction between metal ions and the electrons. These properties of metals make them useful.

1. Be able to describe the nature and arrangement of chemical bonds in metals.

Using the model of metal structure to explain properties of metals.

2. Be able to explain how the bulk properties of metals are related to the type of bonds they contain.

Metallic bonding, properties and uses of metals


Chapter C3.2 How are metals with different reactivities extracted?

Metals can be placed in an order of reactivity by looking at their reactions with water, dilute acid and compounds of other metals. The relative reactivity of metals enables us to make predictions about which metals react fastest or which metal will displace another. When metals react they form ionic compounds. The metal atoms gain one or more electrons to become positive ions. The more easily this happens the more reactive the metal. These reactions can be represented by word and symbol equations including state symbols. Ionic equations show only the ions that change in the reaction and show the gain or loss of electrons. They are useful for representing displacement reactions because they show what happens to the metal ions during the reaction.

The way a metal is extracted depends on its reactivity. Some metals are extracted by reacting the metal compound in their ores with carbon. Carbon is a non-metal but can be placed in the reactivity series of the metals between aluminium and zinc. Metals below carbon in the reactivity series are extracted from their ores by displacement by carbon. The metal in the ore is reduced and carbon is oxidised. Highly reactive metals above carbon in the reactivity series are extracted by electrolysis. Scientists are developing methods of extracting the more unreactive metals from their ores using bacteria or plants. These methods can extract metals from waste material, reduce the need to extract ‘new’ ores, reduce energy costs, and reduce the amount of toxic metals in landfill. However, these methods do not produce large quantities of metals quickly.

1. Be able to deduce an order of reactivity of metals based on experimental results including reactions with water, dilute acid and displacement reactions with other metals.

Practical work:

Investigating the reactivity of different metals with water and dilute acid.

Investigating the reactivity of Zn, Fe and Cu by heating each metal with oxides of each of the other two metals.

Consider the impacts of metal extraction on the environment, the measures scientists are taking to mitigate them, and the risks, costs and benefits of different courses of action.

2. Be able to explain how the reactivity of metals with water or dilute acids is related to the tendency of the metal to form its positive ion to include potassium, sodium, calcium, aluminium, magnesium, zinc, iron, lead, [hydrogen], copper, silver.

3. Be able to use the names and symbols of common elements and compounds and the principle of conservation of mass to write formulae and balanced chemical equations and (HT only) ionic equations.

4. Be able to explain, using the position of carbon in the reactivity series, the principles of industrial processes used to extract metals, including the extraction of zinc.

5. Be able to explain why electrolysis is used to extract some metals from their ores.

6. (HT only) Be able to evaluate alternative biological methods of metal extraction (bacterial and phytoextraction).

The Reactivity Series of Metals

Metal Reactivity Series Experiments-Observations

Introduction to Metal Extraction

Extraction of Zinc

Copper extraction by phytomining or bioleaching


Chapter C3.3 What are electrolytes and what happens during electrolysis?

Electrolysis is used to extract reactive metals from their ores. Electrolysis is the decomposition of an electrolyte by an electric current. Electrolytes include molten and dissolved ionic compounds. In both cases the ions are free to move. During electrolysis non-metal ions lose electrons to the anode to become neutral atoms. Metal (or hydrogen) ions gain electrons at the cathode to become neutral atoms.

The addition or removal of electrons can be used to identify which species are reduced and which are oxidised. These changes can be summarised using half equations.

Electrolysis is used to extract reactive metals from their molten compounds. During the electrolysis of aluminium, aluminium oxide is heated to a very high temperature. Positively charged aluminium ions gain electrons from the cathode to form atoms. Oxygen ions lose electrons at the anode and form oxygen molecules which react with carbon electrodes to form carbon dioxide. The process uses a large amount of energy for both the high temperature and the electricity involved in electrolysis.

Some extraction methods, such as the recovery of metals from waste heaps, give a dilute aqueous solution of metals ions. When an electric current is passed through an aqueous solution the water is electrolysed as well as the ionic compound. Less reactive metals such as silver or copper form on the negative electrode. If the solution contains ions of more reactive metals, hydrogen gas forms from the hydrogen ions from the water. Similarly, oxygen usually forms at the positive electrode from hydroxide ions from the water. A concentrated solution of chloride ions forms chlorine at the positive electrode.

1. Be able to describe electrolysis in terms of the ions present and reactions at the electrodes.

Practical work: Investigating what type of substances are electrolytes.

Introduction to electrolysis - electrolytes, non-electrolytes, electrode equations

2. Be able to predict the products of electrolysis of binary ionic compounds in the molten state.

Electrolysis of molten lead(II) bromide (and other molten ionic compounds)

3. Be able to recall that metals (or hydrogen) are formed at the cathode and non-metals are formed at the anode in electrolysis using inert electrodes.

4. (HT only) Be able to use the names and symbols of common elements and compounds and the principle of conservation of mass to write half equations.

5. (HT only) Be able to explain reduction and oxidation in terms of gain or loss of electrons, identifying which species are oxidised and which are reduced.

Introduction to oxidation and reduction and their application to REDOX reactions

6. Be able to explain how electrolysis is used to extract some metals from their ores including the extraction of aluminium.

Introduction to Metal Extraction

7. Be able to describe competing reactions in the electrolysis of aqueous solutions of ionic compounds in terms of the different species present, including the formation of oxygen, chlorine and the discharge of metals or hydrogen linked to their relative reactivity.

Electrolysis of acidified water (dilute sulfuric acid)

Electrolysis of sodium chloride solution (brine)

Electrolysis of copper(II) sulfate solution

8. Be able to describe the technique of electrolysis of an aqueous solution of a salt.

Practical work: Investigating the effects of concentration of aqueous solution, current, voltage on the electrolysis of sodium chloride.


Chapter C3.4 Why is crude oil important as a source of new materials?

Crude oil is mixture of hydrocarbons. It is used as a source of fuels and as a feedstock for making chemicals (including polymers) for a very wide range of consumer products. Almost all of the consumer products we use involve the use of crude oil in their manufacture or transport. Crude oil is finite. If we continue to burn it at our present rate it will run out in the near future. Crude oil makes a significant positive difference to our lives, but our current use of crude oil is not sustainable. Decisions about the use of crude oil must balance short-term benefits with the need to conserve this resource for the future. Crude oil is a mixture. It needs to be separated into groups of molecules of similar size called fractions. This is done by fractional distillation. Fractional distillation depends on the different boiling points of the hydrocarbons, which in turn is related to the size of the molecules and the intermolecular forces between them. The fractions are mixtures, mainly of alkanes, with a narrow range of boiling points. The first four alkanes show typical properties of a homologous series: each subsequent member increases in size by CH2, they have a general formula and show trends in their physical and chemical properties.

1. Be able to recall that crude oil is a main source of hydrocarbons and is a feedstock for the petrochemical industry.

decision making in the context of the use of crude oil for fuels and as a feedstock.

2. Be able to explain how modern life is crucially dependent upon hydrocarbons and recognise that crude oil is a finite resource.

3. Be able to describe and explain the separation of crude oil by fractional distillation.

Fractional distillation of crude oil & uses of fractions

4. Be able to describe the fractions of crude oil as largely a mixture of compounds of formula CnH2n+2 which are members of the alkane homologous series of hydrocarbons.

Alkanes - saturated hydrocarbons

5. Be able to use ideas about energy transfers and the relative strength of chemical bonds and intermolecular forces to explain the different temperatures at which changes of state occur.

6. Be able to deduce the empirical formula of a compound from the relative numbers of atoms present or from a model or diagram and vice versa.

7. Be able to use arithmetic computation and ratio when determining empirical formulae.

The molecular formula of an alkane shows the number of atoms present in each molecule. These formulae can be simplified to show the simplest ratio of carbon to hydrogen atoms. This type of formula is an empirical formula. Small molecules like alkanes and many of those met in chapter C1 contain non-metal atoms which are bonded to each other by covalent bonds.

A covalent bond is a strong bond between two atoms that formed from a shared pair of electrons. A covalent bond can be represented by a dot and cross diagram. Molecules can be shown as molecular or empirical formulae, displayed formulae (which show all of the bonds in the molecule) or in a 3 dimensional ‘balls and stick’ model.

Simple molecules have strong covalent bonds joining the atoms within the molecule, but they only have weak intermolecular forces. No covalent bonds are broken when simple molecules boil. The molecules move apart when given enough energy to overcome the intermolecular forces. This explains their low melting and boiling points.

8. Be able to describe the arrangement of chemical bonds in simple molecules.

the use and limitations of models to represent bonding in simple molecules

9. Be able to explain covalent bonding in terms of the sharing of electrons.

10. Be able to construct dot and cross diagrams for simple covalent substances.

Covalent bonding and small molecules and their properties

11. Be able to represent three dimensional shapes in two dimensions and vice versa when looking at chemical structures for simple molecules.

12. Be able to describe the limitations of dot and cross diagrams, ball and stick models and two and three dimensional representations when used to represent simple molecules.

13. Be able to translate information between diagrammatic and numerical forms.

14. Be able to explain how the bulk properties of simple molecules are related to the covalent bonds they contain and their bond strengths in relation to intermolecular forces.

Cracking long chain alkanes makes smaller more useful molecules that are in great demand as fuels (for example petrol). Cracking also yields alkenes – hydrocarbons with carbon-carbon double bonds. Alkenes are much more reactive than alkanes and can react to make a very wide range of products including polymers. Without cracking, we would need to extract a lot more crude oil to meet demand for petrol and would waste some longer chain alkanes which are not as useful.

Alkanes - saturated hydrocarbons

15. Be able to describe the production of materials that are more useful by cracking.

cracking as a positive application of science, to reduce extraction of crude oil and so conserves oil reserves

Cracking - a problem of supply and demand, other products

The rest of Chapter C3.4 is for separate science GCSE Chemistry only, NOT combined science.

Alkanes and alkenes burn in plenty of air to make carbon dioxide and water. The double bond makes alkenes more reactive than alkanes. Addition across the double bond means that alkenes decolourise bromine water and can form polymers.

Alkanes - saturated hydrocarbons, reactions including combustion

Alkenes - unsaturated hydrocarbons

An alcohol has a structure like an alkane, but with one hydrogen replaced by an OH group. Alcohols burn to make carbon dioxide and water, and can also be oxidised to make carboxylic acids. All of these compounds are useful to make consumer products. They have different properties due to their different functional groups.

Alkanes do not have a functional group and so are unreactive.

The functional group of alkenes – the double bond – is used for addition reactions.

The OH functional group in alcohols give them a range of uses including their use as solvents that are miscible with water.

The carboxylic acid functional group behaves as a weak acid, and these acids are found in foods and personal care products.

16. (GCSE Chemistry only) Be able to recognise functional groups and identify members of the same homologous series.

Practical work:

Investigating the reactions of alkanes, alkenes and alcohols.

Using of models to represent functional groups in homologous series.

17. (GCSE Chemistry only) Be able to name and draw the structural formulae, using fully displayed formulae, of the first four members of the straight chain alkanes and alkenes, alcohols and carboxylic acids.

Introduction to Organic Chemistry - Why so many series of organic compounds? - homologous series

Alkanes - saturated hydrocarbons, structure and reactions including combustion

Alkenes - unsaturated hydrocarbons - structure and reactions

Alcohols - structures including ethanol - manufacture, properties and reactions

Carboxylic acids and esters, structure and reactions

18. (GCSE Chemistry only) Be able to predict the formulae and structures of products of reactions (combustion, addition across a double bond and oxidation of alcohols to carboxylic acids) of the first four and other given members of these homologous series

19. (GCSE Chemistry only) Be able to recall that it is the generality of reactions of functional groups that determine the reactions of organic compounds


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