BEWARE - this page is for Y10 2016-2017 onwards only!
Old courses AQA GCSE SCIENCES A for Y11 2016-2017
AQA GCSE CHEMISTRY 8462 paper 1 and AQA GCSE Combined Science: Trilogy 8464 Chemistry Paper 1
AQA (9-1) GCSE CHEMISTRY Topics 1-5
The Google [SEARCH] box at the bottom of the page should also prove useful
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 (AQA GCSE chemistry only) means for the separate science, NOT for Combined Science Trilogy 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.
Revision summaries for Paper 1 AQA GCSE Chemistry and AQA GCSE Combined Science: Trilogy Chemistry 1 (this page)
Revision summaries for Paper 2 AQA GCSE Chemistry & AQA GCSE Combined Science: Trilogy Chemistry 2 (separate page)
SUBJECT CONTENT of the syllabus-specification:
TOPICS for Paper 1 AQA GCSE Chemistry and AQA GCSE Combined Science Trilogy: Chemistry 1
Topic 1 Atomic structure and the periodic table (AQA gcse chemistry AQA GCSE combined science trilogy)
Know the periodic table provides chemists with a structured organisation of the known chemical elements from which they can make sense of their physical and chemical properties. The historical development of the periodic table and models of atomic structure provide good examples of how scientific ideas and explanations develop over time as new evidence emerges. The arrangement of elements in the modern periodic table can be explained in terms of atomic structure which provides evidence for the model of a nuclear atom with electrons in energy levels.
1.1 A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes
1.1.1 Atoms, elements and compounds (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that all substances are made of atoms. An atom is the smallest part of an element that can exist. Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium. There are about 100 different elements. Elements are shown in the periodic table. Compounds are formed from elements by chemical reactions. Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed. Compounds can only be separated into elements by chemical reactions. Chemical reactions can be represented by word equations or equations using symbols and formulae. You will be supplied with a periodic table for the exam and you should be able to:
1.1.2 Mixtures (AQA gcse chemistry AQA GCSE combined science trilogy)
A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged. Mixtures can be separated by physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography. These physical processes do not involve chemical reactions. You should be able to:
1.1.3 Scientific models of the atom (common content with physics) (AQA gcse chemistry AQA GCSE combined science)
Appreciate that new experimental evidence may lead to a scientific model being changed or replaced. Before the discovery of the electron atoms were thought to be tiny spheres that could not be divided. The discovery of the electron led to the plum pudding model of the atom. The plum pudding model suggested that the atom was a ball of positive charge with negative electrons embedded in it. The results from the Rutherford and Marsden’s alpha scattering experiments led to the plum pudding model being replaced by the nuclear model. Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with experimental observations. Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles. In 1932 the experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus. This historical context provides an opportunity for you to show an understanding of why and describe how scientific methods and theories develop over time. You should be able to:
1.1.4 Relative electrical charges of subatomic particles (common content with physics)
Know the relative electrical charges of the particles in atoms: proton, neutron and electron. In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge. The number of protons in an atom of an element is its atomic number. All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons. You should be able to use the atomic model to describe atoms.
1.1.5 Size and mass of atoms (common content with physics) (AQA gcse chemistry AQA GCSE combined science trilogy)
Appreciate that atoms are extremely small, having a radius of about 0.1 nm (1 x 10-10 m). The radius of a nucleus is less than 1/10 000 of that of the atom (about 1 x 10-14 m). Almost all of the mass of an atom is in the nucleus. You must know the relative masses of protons, neutrons and electrons. The sum of the protons and neutrons in an atom is its mass number. Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element. Atoms can be represented as shown symbolically e.g. or (upper left = mass number, lower left = atomic number). You should be able to calculate the numbers of protons, neutrons and electrons in an atom or ion, given its atomic number and mass number. Be able to use SI units and the prefix nano. Be able to recognise expressions in standard form. Be able to estimate the size and scale of atoms.
1.1.6 Relative atomic mass (AQA gcse chemistry AQA GCSE combined science trilogy)
The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element.
You should be able to calculate the relative atomic mass of an element given the percentage abundance of its isotopes.
1.1.7 Electronic structure (AQA gcse chemistry AQA GCSE combined science trilogy)
The electrons in an atom occupy the lowest available energy levels (innermost available shells). The electronic structure of an atom can be represented by numbers or by a diagram (on left). For example, the electronic structure of sodium is 2,8,1 or showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level. You may answer questions in terms of either energy levels or shells.
You should be able to work out and represent the electronic structures of the first twenty elements of the periodic table in both forms.
1.2 The periodic table (AQA gcse chemistry AQA GCSE combined science trilogy)
1.2.1 The periodic table
The elements in the periodic table are arranged in order of atomic (proton) number and so that elements with similar properties are in columns, known as groups. The table is called a periodic table because similar properties occur at regular intervals. Elements in the same group in the periodic table have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties. You should be able to:
1.2.2 Development of the periodic table (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of their atomic weights.
The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed.
Mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights.
Elements with properties predicted by Mendeleev were discovered and filled the gaps. Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct.
You should be able to describe these steps in the development of the periodic table and be able to explain how testing a prediction can support or refute a new scientific idea i.e the evolution of the periodic table format.
1.2.3 Metals and non-metals (AQA gcse chemistry AQA GCSE combined science trilogy)
Elements that react to form positive ions are metals. Elements that do not form positive ions are nonmetals. The majority of elements are metals. Metals are found to the left and towards the bottom of the periodic table. Non-metals are found towards the right and top of the periodic table. You should be able to:
1.2.4 Group 0 Noble Gases (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that the elements in Group 0 of the periodic table are called the noble gases. They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons. The noble gases have eight electrons in their outer energy level, except for helium, which has only two electrons. The boiling points of the noble gases increase with increasing relative atomic mass (going down the group). You should be able to:
1.2.5 Group 1 Alkali Metals (AQA gcse chemistry AQA GCSE combined science trilogy)
Know the elements in Group 1 of the periodic table are known as the alkali metals and have characteristic properties because of the single electron in their outer shell.
You should be able to describe the reactions of the first three alkali metals with oxygen, chlorine and water.
In Group 1, the reactivity of the elements increases going down the group.
You should be able to:
1.2.6 Group 7 The halogens (AQA gcse chemistry AQA GCSE combined science trilogy)
Know the elements in Group 7 of the periodic table are known as the halogens and have similar reactions because they all have seven electrons in their outer shell. The halogens are non-metals and consist of molecules made of pairs of atoms.
You should be able to describe the nature of the compounds formed when chlorine, bromine and iodine react with metals and non-metals.
In Group 7, the further down the group an element is the higher its relative molecular mass, melting point and boiling point.
In Group 7, the reactivity of the elements decreases going down the group. A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt - so you can predict the outcome of particular combinations of group 7 element and the salt of another halogen.
You should be able to:
1.3 Properties of transition metals (AQA GCSE chemistry only)
1.3.1 Be able to compare the properties of Group 1 metals with transition metals (AQA GCSE chemistry only)
Know the transition elements are metals with similar properties which are different from those of the elements in Group 1 alkali metals.
You should be able to describe the difference compared with Group 1 in melting points, densities, strength, hardness and reactivity with oxygen, water and halogens.
You should be able to exemplify these general properties by reference to Cr, Mn, Fe, Co, Ni, Cu.
1.3.2 Typical properties of transition metals (AQA GCSE chemistry only)
Know that many transition elements have ions with different charges, form coloured compounds and are useful as catalysts.
You should be able to exemplify these general properties by reference to compounds of Cr, Mn, Fe, Co, Ni, Cu.
Topic 2 Bonding, structure, and the properties of matter (AQA gcse chemistry AQA GCSE combined science trilogy)
Appreciate that chemists use theories of structure and bonding to explain the physical and chemical properties of materials. Analysis of structures shows that atoms can be arranged in a variety of ways, some of which are molecular while others are giant structures. Theories of bonding explain how atoms are held together in these structures. Scientists use this knowledge of structure and bonding to engineer new materials with desirable properties. The properties of these materials may offer new applications in a range of different technologies.
2.1 Chemical bonds, ionic, covalent and metallic
2.1.1 Chemical bonds (AQA gcse chemistry AQA GCSE combined science trilogy)
Know there are three types of strong chemical bonds: ionic, covalent and metallic. For ionic bonding the particles are oppositely charged ions. For covalent bonding the particles are atoms which share pairs of electrons. For metallic bonding the particles are atoms which share delocalised electrons. Ionic bonding occurs in compounds formed from metals combined with non-metals. Covalent bonding occurs in non-metallic elements and in compounds of non-metals. Metallic bonding occurs in metallic elements and alloys. You should be able to explain chemical bonding in terms of electrostatic forces and the transfer or sharing of electrons.
2.1.2 Ionic bonding (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that when a metal atom reacts with a non-metal atom electrons in the outer shell of the metal atom are transferred. Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged ions. The ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0). The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagrams. You need to be able to visualise and represent 2D and 3D forms including two dimensional representations of 3D objects. You should be able to:
2.1.3 Ionic compounds (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that an ionic compound is a giant structure of ions. Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding. Know the structure of sodium chloride can be represented in the following forms: Be able to visualise and represent 2D and 3D forms including two dimensional representations of 3D objects. You should be able to:
You should be familiar with the structure of sodium chloride but do not need to know the structures of other ionic compounds.
2.1.4 Covalent bonding (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that when atoms share pairs of electrons, they form covalent bonds. These bonds between atoms are strong. Covalently bonded substances may consist of small molecules.
You should be able to recognise common substances that consist of small molecules from their chemical formula.
Some covalently bonded substances have very large molecules, such as polymers.
Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide.
Be able to represent the covalent bonds in molecules and giant structures in various forms.
Recognise substances as small molecules, polymers or giant structures from diagrams showing their bonding
You should be able to:
2.1.5 Metallic bonding (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that metals consist of giant structures of atoms arranged in a regular pattern. The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds. The bonding in metals may be represented in the following form: Be able to recognise substances as metallic giant structures from diagrams showing their bonding. Be able to visualise and represent 2D and 3D forms including two dimensional representations of 3D objects.
2.2 How bonding and structure are related to the properties of substances
2.2.1 The three states of matter (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that the three states of matter are solid, liquid and gas. Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point.
The three states of matter can be represented by a simple model. In this model, particles are represented by small solid spheres. Particle theory can help to explain melting, boiling, freezing and condensing. The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance.
(HT only) Limitations of the simple model include that there are no forces between the spheres, that all particles are represented as spheres and that the spheres are solid.
Be able to visualise and represent 2D and 3D forms including two dimensional representations of 3D objects. You should be able to:
2.2.2 State symbols
Know that in chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions. You should be able to include appropriate state symbols in chemical equations for the reactions in this specification.
2.2.3 Properties of ionic compounds (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions.
These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds.
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
Knowledge of the structures of specific ionic compounds other than sodium chloride is not required.
2.2.4 Properties of small molecules (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
These substances have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
These substances do not conduct electricity because the molecules do not have an overall electric charge.
You should be able to use the idea that intermolecular forces are weak compared with covalent bonds to explain the bulk properties of molecular substances.
2.2.5 Polymers (AQA gcse chemistry AQA GCSE combined science trilogy)
Appreciate that polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
You should be able to recognise polymers from diagrams showing their bonding and structure.
2.2.6 Giant covalent structures (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that substances that consist of giant covalent structures are solids with very high melting points. All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
Be able to recognise giant covalent structures from diagrams showing their bonding.
Be able to visualise and represent 2D and 3D forms including two dimensional representations of 3D objects.
2.2.7 Properties of metals and alloys (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that metals have giant structures of atoms with strong metallic bonding. This means that most metals have high melting and boiling points.
In metals, the layers of atoms are able to slide over each other. This means metals can be bent and shaped.
Most metals in everyday use are alloys. Pure metals eg copper, gold, iron and aluminium, are too soft for many uses and so are mixed with other metals to make alloys which are harder.
The different sizes of atoms in an alloy distort the layers in the structure, making it more difficult for them to slide over each other, so alloys are harder than pure metals. You should be able to explain why an alloy of a metal is harder than the pure metal.
2.2.8 Metals as conductors (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal. Metals are good conductors of thermal energy because energy is transferred by the mobile delocalised electrons.
2.3 Structure and bonding of carbon
2.3.1 Diamond (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that in diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard, has a very high melting point and does not conduct electricity. Be able to explain the properties of diamond in terms of its structure and bonding. Be able to visualise and represent 2D and 3D forms including two dimensional representations of 3D objects.
2.3.2 Graphite (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that in graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers. In graphite, one electron from each carbon atom is delocalised.
You should be able to explain the properties of graphite in terms of its structure and bonding.
You should know that graphite is similar to metals in that it has delocalised electrons.
2.3.3 Graphene and fullerenes (AQA gcse chemistry AQA GCSE combined science trilogy)
Graphene is a single layer of graphite and has properties that make it useful in electronics and composites.
You should be able to explain the properties of graphene in terms of its structure and bonding.
Fullerenes are molecules of carbon atoms with hollow shapes. The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms. The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.
Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials. You should be able to:
2.4 Bulk and surface properties of matter including nanoparticles (AQA GCSE chemistry only)
2.4.1 Sizes of particles and their properties (AQA GCSE chemistry only)
Nanoscience refers to structures that are 1–100 nm in size, of the order of a few hundred atoms. Nanoparticles, are smaller than fine particles (PM2.5), which have diameters between 100 and 2500 nm (1 x 10-7 m and 2.5 x 10-6 m).
Coarse particles (PM10) have diameters between 1 x 10-5 m and 2.5 x 10-6 m. Coarse particles are often referred to as dust.
As the side of cube decreases by a factor of 10 the surface area to volume ratio increases by a factor of 10.
Nanoparticles may have properties different from those for the same materials in bulk because of their high surface area to volume ratio. It may also mean that smaller quantities are needed to be effective than for materials with normal particle sizes.
You should be able to compare ‘nano’ dimensions to typical dimensions of atoms and molecules.
Be able to
2.4.2 Uses of nanoparticles (AQA GCSE chemistry only)
Nanoparticles have many applications in medicine, in electronics, in cosmetics and sun creams, as deodorants, and as catalysts. New applications for nanoparticulate materials are an important area of research.
You should consider advantages and disadvantages of the applications of these nanoparticulate materials, but do not need to know specific examples or properties other than those specified.
You should be able to:
Topic 3 Quantitative chemistry (AQA gcse chemistry AQA GCSE combined science trilogy)
Chemists use quantitative analysis to determine the formulae of compounds and the equations for reactions. Given this information, analysts can then use quantitative methods to determine the purity of chemical samples and to monitor the yield from chemical reactions.
Chemical reactions can be classified in various ways. Identifying different types of chemical reaction allows chemists to make sense of how different chemicals react together, to establish patterns and to make predictions about the behaviour of other chemicals.
Chemical equations provide a means of representing chemical reactions and are a key way for chemists to communicate chemical ideas.
3.1 Conservation of mass and the quantitative interpretation of chemical equations
3.1.1 Conservation of mass and balanced chemical equations
Know the law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.
This means that chemical reactions can be represented by symbol equations which are balanced in terms of the numbers of atoms of each element involved on both sides of the equation.
You should understand the use of the multipliers in equations in normal script before a formula and in subscript within a formula.
3.1.2 Relative formula mass (AQA gcse chemistry AQA GCSE combined science trilogy)
Know the relative formula mass (Mr) of a compound is the sum of the relative atomic masses of the atoms in the numbers shown in the formula.
In a balanced chemical equation, the sum of the relative formula masses of the reactants in the quantities shown equals the sum of the relative formula masses of the products in the quantities shown.
3.1.3 Mass changes when a reactant or product is a gas (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that some reactions may appear to involve a change in mass but this can usually be explained because a reactant or product is a gas and its mass has not been taken into account.
For example: when a metal reacts with oxygen the mass of the oxide produced is greater than the mass of the metal or in thermal decompositions of metal carbonates carbon dioxide is produced and escapes into the atmosphere leaving the metal oxide as the only solid product.
You should be able to explain any observed changes in mass in non-enclosed systems during a chemical reaction given the balanced symbol equation for the reaction and explain these changes in terms of the particle model.
You should have experienced investigating of mass changes using various apparatus.
3.1.4 Chemical measurements (AQA gcse chemistry AQA GCSE combined science trilogy)
Whenever a measurement is made there is always some uncertainty about the result obtained. You should be able to:
3.2 Use of amount of substance in relation to masses of pure substances
3.2.1 Moles (HT only) (AQA gcse chemistry AQA GCSE combined science trilogy)
Chemical amounts are measured in moles. The symbol for the unit mole is mol.
The mass of one mole of a substance in grams is numerically equal to its relative formula mass.
One mole of a substance contains the same number of the stated particles, atoms, molecules or ions as one mole of any other substance.
The number of atoms, molecules or ions in a mole of a given substance is the Avogadro constant. The value of the Avogadro constant is 6.02 x 1023 per mole.
You should understand that the measurement of amounts in moles can apply to atoms, molecules, ions, electrons, formulae and equations, for example that in one mole of carbon (C) the number of atoms is the same as the number of molecules in one mole of carbon dioxide (CO2).
You should be able to use the relative formula mass of a substance to calculate the number of moles in a given mass of that substance and vice versa.
Be able to recognise and use expressions in decimal form. Be able to recognise and use expressions in standard form.
Be able to use an appropriate number of significant figures.
Be able to understand and use the symbols: =, <, <<, >>, >, , ~
Be able to change the subject of an equation.
3.2.2 Amounts of substances in equations (HT only) (AQA gcse chemistry AQA GCSE combined science trilogy)
The masses of reactants and products can be calculated from balanced symbol equations. Chemical equations can be interpreted in terms of moles. For example: Mg + 2HCI ===> MgCI2 + H2 shows that one mole of magnesium reacts with two moles of hydrochloric acid to produce one mole of magnesium chloride and one mole of hydrogen gas. You should be able to:
3.2.3 Using moles to balance equations (HT only) (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that the balancing numbers in a symbol equation can be calculated from the masses of reactants and products by converting the masses in grams to amounts in moles and converting the numbers of moles to simple whole number ratios. You should be able to:
3.2.4 Limiting reactants (HT only) (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that in a chemical reaction involving two reactants, it is common to use an excess of one of the reactants to ensure that all of the other reactant is used. The reactant that is completely used up is called the limiting reactant because it limits the amount of products.
You should be able to explain the effect of a limiting quantity of a reactant on the amount of products it is possible to obtain in terms of amounts in moles or masses in grams.
3.2.5 Concentration of solutions (HT only) (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that many chemical reactions take place in solutions. The concentration of a solution can be measured in mass per given volume of solution, eg grams per dm3 (g/dm3). You should be able to:
3.3 Yield and atom economy of chemical reactions (AQA GCSE chemistry only)
3.3.1 Percentage yield (AQA GCSE chemistry only)
Know that even though no atoms are gained or lost in a chemical reaction, it is not always possible to obtain the calculated amount of a product because:
The amount of a product obtained is known as the yield.
When compared with the maximum theoretical amount as a percentage, it is called the percentage yield.
% Yield = 100 x Mass of product actually made ÷ Maximum theoretical mass of product
(HT only) Be able to calculate the theoretical mass of a product from a given mass of reactant and the balanced equation for the reaction
3.3.2 Atom economy (AQA GCSE chemistry only)
Know the atom economy (atom utilisation) is a measure of the amount of starting materials that end up as useful products. It is important for sustainable development and for economic reasons to use reactions with high atom economy.
The percentage atom economy of a reaction is calculated using the balanced equation for the reaction as follows:
100 x Relative formula mass of desired product from equation ÷ Sum of relative formula masses of all reactants from equation
You should be able to:
3.4 Using concentrations of solutions in mol/dm3 (AQA GCSE chemistry only) (HT only)
Know that the concentration of a solution can be measured in mol/dm3.
The amount in moles of solute or the mass in grams of solute in a given volume of solution can be calculated from its concentration in mol/dm3.
If the volumes of two solutions that react completely are known and the concentration of one solution is known, the concentration of the other solution can be calculated.
The volumes of acid and alkali solutions that react with each other can be measured by titration using a suitable indicator.
You should be able to:
You should have experienced doing titrations including to determine concentrations of strong acids and alkalis.
3.5 Use of amount of substance in relation to volumes of gases (AQA GCSE chemistry only) (HT only)
Know that equal amounts in moles of gases occupy the same volume under the same conditions of temperature and pressure.
The volume of one mole of any gas at room temperature and pressure (20oC and 1 atmosphere pressure) is 24 dm3.
The volumes of gaseous reactants and products can be calculated from the balanced equation for the reaction.
You should be able to:
You should be able to:
Topic 4 Chemical changes (AQA gcse chemistry AQA GCSE combined science trilogy)
Appreciate that understanding of chemical changes began when people began experimenting with chemical reactions in a systematic way and organizing their results logically. Knowing about these different chemical changes meant that scientists could begin to predict exactly what new substances would be formed and use this knowledge to develop a wide range of different materials and processes. It also helped biochemists to understand the complex reactions that take place in living organisms. The extraction of important resources from the earth makes use of the way that some elements and compounds react with each other and how easily they can be ‘pulled apart’.
4.1 Reactivity of metals (AQA gcse chemistry AQA GCSE combined science trilogy)
4.1.1 Metal oxides
Know that metals react with oxygen to produce metal oxides.
The reactions are oxidation reactions because the metals gain oxygen.
You should be able to explain reduction and oxidation in terms of loss or gain of oxygen.
4.1.2 The reactivity series
Know that when metals react with other substances the metal atoms form positive ions. The reactivity of a metal is related to its tendency to form positive ions. Metals can be arranged in order of their reactivity in a reactivity series.
The metals potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper can be put in order of their reactivity from their reactions with water and dilute acids.
The non-metals hydrogen and carbon are often included in the reactivity series.
A more reactive metal can displace a less reactive metal from a compound. You should be able to:
The reactions of metals with water and acids are limited to room temperature and do not include reactions with steam.
4.1.3 Extraction of metals and reduction (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that unreactive metals such as gold are found in the Earth as the metal itself but most metals are found as compounds that require chemical reactions to extract the metal.
Metals less reactive than carbon can be extracted from their oxides by reduction with carbon.
Reduction involves the loss of oxygen.
Your knowledge and understanding are limited to the reduction of oxides using carbon.
Knowledge of the details of processes used in the extraction of metals is not required.
You should be able to:
4.1.4 Oxidation and reduction in terms of electrons (HT only, AQA gcse chemistry AQA GCSE combined science trilogy)
Know that oxidation is the loss of electrons and reduction is the gain of electrons.
You should be able to:
4.2 Reactions of acids (AQA gcse chemistry AQA GCSE combined science trilogy)
4.2.1 Reactions of acids with metals (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that acids react with some metals to produce salts and hydrogen.
(HT only) You should be able to:
Knowledge of reactions limited to those of magnesium, zinc and iron with hydrochloric and sulfuric acids.
4.2.2 Neutralisation of acids and salt production (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that acids are neutralised by alkalis (eg soluble metal hydroxides) and bases (eg insoluble metal hydroxides and metal oxides) to produce salts and water, and also neutralised by metal carbonates to produce salts, water and carbon dioxide.
The particular salt produced in any reaction between an acid and a base or alkali depends on:
You should be able to:
4.2.3 Soluble salts (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that soluble salts can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides or carbonates.
The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt.
Salt solutions can be crystallised to produce solid salts.
You should be able to describe how to make pure, dry samples of named soluble salts from information provided.
You should have prepared of a pure, dry sample of a soluble salt from an insoluble oxide or carbonate using a bunsen burner to heat dilute acid and a water bath or electric heater to evaporate the solution.
4.2.4 The pH scale and neutralisation (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that acids produce hydrogen ions (H+) in aqueous solutions.
Aqueous solutions of alkalis contain hydroxide ions (OH–).
The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution, and can be measured using universal indicator or a pH probe.
A solution with pH 7 is neutral. Aqueous solutions of acids have pH values of less than 7 and aqueous solutions of alkalis have pH values greater than 7.
In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water.
You should be able to:
You should have investigated pH changes when a strong acid neutralises a strong alkali.
4.2.5 Titrations (AQA GCSE chemistry only)
The volumes of acid and alkali solutions that react with each other can be measured by titration using a suitable indicator. You should be able to:
You should have done the practical to determine the reacting volumes of solutions of a strong acid and a strong alkali by titration.
(HT only) Be able to determine the concentration of one of the solutions in mol/dm3 and g/dm3 from the reacting volumes and the known concentration of the other solution.
4.2.6 Strong and weak acids (HT only)
Know that a strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.
A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids.
For a given concentration of aqueous solutions, the stronger an acid, the greater the hydrogen ion concentration and the lower the pH.
As the pH decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10.
You should be able to:
4.3 Electrolysis (AQA gcse chemistry AQA GCSE combined science trilogy)
4.3.1 The process of electrolysis
Know that when an ionic compound is melted or dissolved in water, the ions are free to move about within the liquid or solution. These liquids and solutions are able to conduct electricity and are called electrolytes.
Passing an electric current through electrolytes causes the ions to move to the electrodes. Positively charged ions move to the negative electrode (the cathode), and negatively charged ions move to the positive electrode (the anode).
Ions are discharged at the electrodes producing elements. This process is called electrolysis.
(HT only) Throughout Section 4.3 you should be able to write half equations for the reactions occurring at the electrodes during electrolysis, and you may be required to complete and balance supplied half equations.
4.3.2 Electrolysis of molten ionic compounds (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that when a simple ionic compound (eg lead bromide) is electrolysed in the molten state using inert electrodes, the metal (lead) is produced at the cathode and the non-metal (bromine) is produced at the anode.
You should be able to predict the products of the electrolysis of binary ionic compounds in the molten state.
Your teacher may have demonstrated this kind of electrolysis using anhydrous zinc chloride.
4.3.3 Using electrolysis to extract metals (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that metals can be extracted from molten compounds using electrolysis. Electrolysis is used if the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon. Large amounts of energy are used in the extraction process to melt the compounds and to produce the electrical current.
Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite. The mixture has a lower melting point than pure aluminium oxide. Aluminium forms at the negative electrode (cathode) and oxygen at the positive electrode (anode). The positive electrode (anode) is made of carbon, which reacts with the oxygen to produce carbon dioxide and so must be continually replaced.
You should be able to:
4.3.4 Electrolysis of aqueous solutions (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that the ions discharged when an aqueous solution is electrolysed using inert electrodes depend on the relative reactivity of the elements involved.
At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen.
At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced.
You should be able to predict the products of the electrolysis of aqueous solutions containing a single ionic compound.
You should have investigated what happens when aqueous solutions are electrolysed using inert electrodes.
4.3.5 Representation of reactions at electrodes as half equations (HT only)
Know that during electrolysis, at the cathode (negative electrode), positively charged ions gain electrons and so the reactions are reductions.
At the anode (positive electrode), negatively charged ions lose electrons and so the reactions are oxidations.
Reactions at electrodes can be represented by half equations, for example:
Topic 5 Energy changes (AQA gcse chemistry AQA GCSE combined science trilogy)
Appreciate that energy changes are an important part of chemical reactions. The interaction of particles often involves transfers in energy due to the breaking and formation of bonds. Reactions in which energy is released to the surroundings are exothermic reactions, while those that take in heat (absorb) thermal energy are endothermic.
These interactions between particles can produce heating or cooling effects that are used in a range of everyday applications.
Some interactions between ions in an electrolyte result in the production of electricity.
Cells and batteries use these chemical reactions to generate electricity.
Electricity can also be used to decompose (split) ionic substances and is a useful means of producing elements that are too expensive to extract any other way.
5.1 Exothermic and endothermic reactions (AQA gcse chemistry AQA GCSE combined science trilogy)
5.1.1 Energy transfer during exothermic and endothermic reactions
Know that energy is conserved in chemical reactions. The amount of energy in the universe at the end of a chemical reaction is the same as before the reaction takes place. If a reaction transfers energy to the surroundings the product molecules must have less energy than the reactants, by the amount transferred.
An exothermic reaction is one that transfers energy to the surroundings so the temperature of the surroundings increases. Exothermic reactions include combustion, many oxidation reactions and neutralisation. Everyday uses of exothermic reactions include selfheating cans and hand warmers.
An endothermic reaction is one that takes in energy from the surroundings so the temperature of the surroundings decreases. Endothermic reactions include thermal decompositions and the reaction of citric acid and sodium hydrogencarbonate. Some sports injury packs are based on endothermic reactions.
You should be able to:
You should have investigated the variables that affect temperature changes in reacting solutions such as, eg acid plus metals, acid plus carbonates, neutralisations and displacement of metals.
5.1.2 Reaction profiles (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that chemical reactions can occur only when reacting particles collide with each other and with sufficient energy. The minimum amount of energy that particles must have to react is called the activation energy.
Reaction profiles can be used to show the relative energies of reactants and products, the activation energy and the overall energy change of a reaction.
You should be able to:
5.1.3 The energy change of reactions (HT only) (AQA gcse chemistry AQA GCSE combined science trilogy)
Know that during a chemical reaction:
The energy needed to break bonds and the energy released when bonds are formed can be calculated from bond energies.
The difference between the sum of the energy needed to break bonds in the reactants and the sum of the energy released when bonds in the products are formed is the overall energy change of the reaction.
In an exothermic reaction, the energy released from forming new bonds is greater than the energy needed to break existing bonds.
In an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds.
You should be able to calculate the energy transferred in chemical reactions using bond energies supplied.
5.2 Chemical cells and fuel cells (AQA GCSE chemistry only)
5.2.1 Cells and batteries (AQA GCSE chemistry only)
Know that cells contain chemicals which react to produce electricity. The voltage produced by a cell is dependent upon a number of factors including the type of electrode and electrolyte.
A simple cell can be made by connecting two different metals in contact with an electrolyte.
Batteries consist of two or more cells connected together in series to provide a greater voltage. In non-rechargeable cells and batteries the chemical reactions stop when one of the reactants has been used up. Alkaline batteries are non-rechargeable.
You should be able to interpret data for relative reactivity of different metals and evaluate the use of cells.
You do not need to know details of cells and batteries other than those specified.
You should have experienced the safe and careful use of liquids.
5.2.2 Fuel cells (AQA GCSE chemistry only)
Know that fuel cells are supplied by an external source of fuel (eg hydrogen) and oxygen or air. The fuel is oxidised electrochemically within the fuel cell to produce a potential difference.
The overall reaction in a hydrogen fuel cell involves the oxidation of hydrogen to produce water.
Hydrogen fuel cells offer a potential alternative to rechargeable cells and batteries.
You should be able to:
Doc Brown's Science Website
Help links for the 'old' GCSE science courses finish in June 2017
(NOT for Y10 2016 students onwards)
'old' AQA GCSE SCIENCES (including separate GCSE biology, GCSE chemistry and GCSE physics)
'old' EDEXCEL GCSE SCIENCES (including separate GCSE biology, GCSE chemistry and GCSE physics)
'old' OCR GCSE 21st Century SCIENCES A (including separate GCSE biology, GCSE chemistry and GCSE physics)
'old' OCR GCSE Gateway SCIENCES B (including separate GCSE biology, GCSE chemistry and GCSE physics)
Doc Brown's Chemistry
For latest updates see https://twitter.com/docbrownchem
visits since January 2000
Enter specific science words or science course e.g. topic, module, exam board syllabus or paper (AQA, Edexcel, OCR 21st Century/Gateway Science), formula, concept, equation, 'phrase', name of anything in biology, physics or chemistry, your latest homework question! anything of scientific interest!