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OCR Level 1/2 GCSE (9–1) in Chemistry A (Gateway Science) (J248) Foundation Tier Paper 1/Higher Tier Paper 3
and OCR Level 1/2 GCSE (9–1) in Combined Science A (Gateway Science) (J250) FT Paper 3/HT Paper 9 Chemistry
OCR (9-1) Gateway GCSE CHEMISTRY A Chapters C1, C2 and C3
'Old' OCR Gateway GCSE sciences for Y11 finishing Y11 2016-2017
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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 GCSE 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.
Revision summaries for GCSE Chemistry FT Paper 1/HT Paper 3
AND GCSE Combined Science FT Paper 3/HT Paper 9 (this page)
Summaries for GCSE Chemistry FT Paper 2/HT Paper 4
AND GCSE Combined Science FT Paper 4/HT Paper 10 (separate page)
TOPICS OCR GCSE Chemistry A FT Paper 1/HT Paper 3
AND GCSE Combined Science A FT Paper 3/HT Paper 9 (Gateway Science)
Topic C1: Particles
C1.1 The particle model
Appreciate you can use a particle model to explain the different states of matter. A simple particle model can be to used to represent the arrangement of particles in the different states of matter and to explain observations during changes in state. It does not, however, explain why different materials have different properties. This explanation is that the particles themselves and how they are held together must be different in some way. Elements are substances that are made up of only one type of atom and atoms of different elements can combine to make compounds. You should be familiar with the different states of matter and their properties. You should also be familiar with changes of state in terms of the particle model. You should have sufficient understanding of the particle model to be able to apply it to unfamiliar materials and contexts. Common misconceptions - the idea that matter is continuous eg the space between gas particles is filled or non-existent, or that particles expand when they are heated. You also need to appreciate the concept of changes in state being reversible. Other problem concepts might be when you represent three dimensional shapes in two dimensions and vice versa when looking at chemical structures e.g. allotropes of carbon.
C1.1a Be able to describe the main features of the particle model in terms of states of matter and change of state
C1.1b Be able to explain in terms of the particle model the distinction between physical changes and chemical changes
C1.1c Be able to explain the limitations of the particle model in relation to changes of state when particles are represented by inelastic spheres (e.g. like bowling balls). Appreciate that it does not take into account the forces of attraction between particles, the size of particles and the space between them.
C1.2 Atomic structure
An atom is the smallest component of an element that gives an element its property. These properties can be explained by models of atomic structure. Current models suggest that atoms are made of smaller sub-atomic particles called protons, neutrons and electrons. The models suggest that atoms are composed of a nucleus surrounded by electrons. The nucleus is composed of neutrons and protons. Atoms of each element have the same number of protons as electrons. Atoms of different elements have different numbers of protons. Atoms of the same element will have the same number of protons but may have different numbers of neutrons. Common misconceptions: understanding the concept of isotopes due to the fact you may think that neutral atoms have the same number of protons and neutrons. You may find it difficult to distinguish between the properties of atoms and molecules. Another common misconception is that a positive ion gains protons or a negative ion loses electrons i.e. that there is a change in the nucleus of the atom rather than a change in the number of electrons. Be able to relate size and scale of atoms to objects in the physical world and be able to estimate size and scale of atoms and nanoparticles
C1.2a Be able to describe how and why the atomic model has changed over time including the models of Dalton, Thomson, Rutherford, Bohr, Geiger and Marsden.
C1.2b 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
C1.2c Know the typical size (order of magnitude) of atoms and small molecules - the concept that typical atomic radii and bond length are in the order of 10-10m
C1.2d Know the relative charges and approximate relative masses of protons, neutrons and electrons
C1.2e Be able to calculate numbers of protons, neutrons and electrons in atoms and ions, given atomic number and mass number of isotopes. Know the definitions of an ion, atomic number, mass number and an isotope and the standard notation to represent these terms.
Topic C2 Elements, compounds and mixtures
C2.1 Purity and separating mixtures
Know in chemical terms elements and compounds are pure substances and mixtures are impure substances. Chemically pure substances can be identified using melting point. Many useful materials that we to use today are mixtures. There are many methods of separating mixtures including filtration, crystallisation, distillation and chromatographic techniques. You should be familiar with the concept of pure substances. You should have met simple separation techniques of mixtures. Know about the identification of pure substances in terms of melting point, boiling point and chromatography. Common misconceptions don't confuse the word pure and with natural (untampered with). Don't think that when a substance dissolves that the solution is pure and not a mixture.
C2.1a Be able to explain what is meant by the purity of a substance, distinguishing between the scientific and everyday Be able to use of the term ‘pure’. Practical on purifying compounds.
C2.1b Be able to use melting point data to distinguish pure from impure substances. Practical - measurement of melting point.
C2.1c Be able to calculate relative formula masses of species separately and in a balanced chemical equation. Know the definition of relative atomic mass, relative molecular mass and relative formula mass
C2.1d 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
C2.1e Be able to explain that many useful materials are formulations of mixtures including alloys.
C2.1f Be able to describe and exemplify the processes of filtration, crystallisation, simple distillation, and fractional distillation - know the techniques of filtration, crystallisation, simple distillation and fractional distillation.
C2.1g Be able to describe the techniques of paper and thin layer chromatography - practical exercise using these techniques.
C2.1h Know that chromatography involves a stationary and a mobile phase and that separation depends on the distribution between the phases - identification of the mobile and stationary phases
C2.1i Be able to interpret chromatograms, including measuring Rf values know and use of the Rf formula.
C2.1j Be able to suggest suitable purification techniques given information about the substances involved
C2.1k Be able to suggest chromatographic methods for distinguishing pure from impure substances including paper, thin layer (TLC) and gas chromatography. Practical - using chromatography to identify mixtures of dyes in an unknown ink.
A simple electron energy level model can be used to explain the basic chemical properties of elements. When chemical reactions occur, they can be explained in terms of losing, gaining or sharing of electrons. The ability of an atom to lose, gain or share electrons depends on its atomic structure. Atoms that lose electrons will bond with atoms that gain electrons. Electrons will be transferred between the atoms to form a positive ion and a negative ion. These ions attract one another in what is known as an ionic bond. Atoms that share electrons can bond with other atoms that share electrons to form a molecule. Atoms in these molecules are held together by covalent bonds. You should be familiar with the simple (Dalton) atomic model. Common misconceptions - appreciate that the nucleus of an atom does not change when an electron is lost, gained or shared, its sometimes difficult to predict the numbers of atoms that must bond in order to achieve a stable outer level of electrons, don't think chemical bonds are physical things made of matter (they are forces between particles). Don't think that pairs of ions such as Na+ and Cl– are molecules. Be aware of the 3D nature of bonding and therefore the shape of molecules. Be able to estimate size and scale of atoms and nanoparticles and be able to represent three dimensional shapes in two dimensions and vice versa when looking at chemical structures e.g. allotropes of carbon. You may also have to translate information between diagrammatic and numerical forms.
C2.2a Be able to describe metals and non-metals and be able to explain the differences between them on the basis of their characteristic physical and chemical properties including physical properties, formation of ions and common reactions e.g. with oxygen to form oxides.
C2.2b Be able to explain how the atomic structure of metals and non-metals relates to their position in the Periodic Table
C2.2c 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 - reference to group number and period number.
C2.2d/C2.2f Be able to describe and compare the nature and arrangement of chemical bonds in:
C2.2e/C2.2g Be able to explain chemical bonding in terms of electrostatic forces and the transfer or sharing of electrons
C2.2f/C2.2h Be able to construct dot and cross diagrams for simple covalent and binary ionic substances
C2.2g/C2.2i Be able to describe the limitations of particular representations and models to include dot and cross diagrams, ball and stick models and two and three dimensional representations.
C2.2h/C2.2d 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
C2.2i/C2.2e Be able to explain in terms of atomic number how Mendeleev’s arrangement was refined into the modern Periodic Table
C2.3 Properties of materials
This section explores the physical properties of elements and compounds and how the nature of their bonding is a factor in their properties. You should know the difference between an atom, element and compound. Common misconceptions - you have a limited understanding of chemical reactions, for example substances may explode, burn, contract, expand or change state.
C2.3a Know that carbon can form four covalent bonds
C2.3b Be able to explain that the vast array of natural and synthetic organic compounds occur due to the ability of carbon to form families of similar compounds, chains and rings.
C2.3c Be able to explain the properties of diamond, graphite, fullerenes and graphene in terms of their structures and bonding.
C2.3d 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
C2.3e Be able to use data to predict states of substances under given conditions using data such as temperature and how this may be linked to changes of state
C2.3f Be able to explain how the bulk properties of materials (ionic compounds; simple molecules; giant covalent structures; polymers and metals) are related to the different types of bonds they contain, their bond strengths in relation to intermolecular forces and the ways in which their bonds are arranged. You should recognise that the atoms themselves do not have the bulk properties of these materials
C2.3g (GCSE chemistry only) compare ‘nano’ dimensions to typical dimensions of atoms and molecules
C2.3h (GCSE chemistry only) Be able to describe the surface area to volume relationship for different-sized particles and be able to describe how this affects properties - practical on dissolving tablets.
C2.3i (GCSE chemistry only) Be able to describe how the properties of nanoparticulate materials are related to their to uses
C2.3j (GCSE chemistry only) Be able to explain the possible risks associated with some nanoparticulate materials
Topic C3 Chemical reactions
C3.1 Introducing chemical reactions
A chemical equation represents, in symbolic terms, the overall change in a chemical reaction. New materials are formed through chemical reactions but mass will be conserved. This can be explained by a model involving the rearrangement of atoms. Avogadro gave us a system of measuring the amount of a substance in moles. You should be familiar with chemical symbols and formulae for elements and compounds, representing chemical reactions using formulae and knowledge of conservation of mass, changes of state and chemical reactions. You may have to do calculations with numbers written in standard form when using the Avogadro and be able to convert units where appropriate particularly from mass to moles.
C3.1a Be able to use chemical symbols to write the formulae of elements and simple covalent and ionic compounds
C3.1b 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) half equations
C3.1c Be able to use the names and symbols of common elements from a supplied Periodic Table to write formulae and balanced chemical equations where appropriate including the first 20 elements, group 1, 7, and 0 and other common elements included within the specification.
C3.1d Be able to use the formula of common ions to deduce the formula of a compound
C3.1e (HT only) Be able to construct balanced ionic equations
C3.1f Be able to describe the physical states of products and reactants using state symbols (s, l, g and aq)
C3.1g/C3.1h (HT only) Know and be able to use the definitions of the Avogadro constant (in standard form) and of the mole including the calculation of the mass of one atom/molecule
C3.1g Be able to describe tests to identify selected gases - oxygen, hydrogen, carbon dioxide and chlorine (Combined Science only in Topic 3.1, covered in Topic 4.2 for GCSE chemistry)
C3.1h/C3hi (HT only) Be able to explain how the mass of a given substance is related to the amount of that substance in moles and vice versa
C3.1i/C3.1i Know and be able to use the law of conservation of mass.
C3.1j/C3,1l Be able to explain any observed changes in mass in non-enclosed systems during a chemical reaction and be able to explain them using the particle model
C3.1j (HT only) Be able to explain how the mass of a solute and the volume of the solution is related to the concentration of the solution (Combined Science only in Topic 3, covered in Topic 5.1 for GCSE chemistry)
C3.1k/C3.1m (HT only) Be able to deduce the stoichiometry of an equation from the masses of reactants and products and be able to explain the effect of a limiting quantity of a reactant.
C3.1l/C3.1n (HT only) Be able to use a balanced equation to calculate masses of reactants or products.
Chemical reactions are accompanied by an energy change. A simple model involving the breaking and making of chemical bonds can be used to interpret and calculate the energy change. You should be familiar with exothermic and endothermic chemical reactions. Common misconceptions - energy is lost or used up rather than energy is transferred, thinking that energy is released when bonds break and do not link this release of energy with the formation of bonds and don't that eg a candle burning is endothermic because heat is needed to initiate the reaction. You are expected to be able to calculations involving energy changes.
C3.2a Be able to distinguish between endothermic and exothermic reactions on the basis of the temperature change of the surroundings - practical measuring the temperature change in reactions.
C3.2b Be able to draw and label a reaction profile for an exothermic and an endothermic reaction including activation energy, energy change, reactants and products.
C3.2c Be able to explain activation energy as the energy needed for a reaction to occur.
C3.2d (HT only) Be able to calculate energy changes in a chemical reaction by considering bond making and bond breaking energies
C3.3 Types of chemical reactions
Chemical reactions can be classified according to changes at the atomic and molecular level. Examples of these include reduction, oxidation and neutralisation reactions. You should be familiar with combustion, thermal decomposition, oxidation and displacement reactions. You should be familiar with defining acids and alkalis in terms of neutralisation reactions eg reactions of acids with alkalis to produce a salt and water and reactions of acids with metals to produce a salt and hydrogen. Common misconceptions - hydrogen ions in an acid are still part of the molecule, not free in the solution. pH is often misunderstood and alkalis are seen as less corrosive than acids. A big misconception is that the strength of acids and bases and concentration mean the same thing - they do NOT, so take care on these ideas.
C3.3a Be able to explain reduction and oxidation in terms of loss or gain of oxygen, identifying which species are oxidised and which are reduced including the concept of oxidising agent and reducing agent.
C3.3b (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.
C3.3c Know that acids form hydrogen ions when they dissolve in water and solutions of alkalis contain hydroxide ions.
C3.3d Be able to describe neutralisation as acid reacting with alkali or a base to form a salt plus water.
C3.3e Recognise that aqueous neutralisation reactions can be generalised to hydrogen ions reacting with hydroxide ions to form water.
C3.3f Know that carbonates and some metals react with acids and write balanced equations predicting products from given reactants.
C3.3g (HT only) Be able to use and explain the terms dilute and concentrated (amount of substance) and weak and strong (degree of ionisation) in relation to acids - ratio of amount of acid to volume of solution.
C3.3h Know that relative acidity and alkalinity are measured by pH
C3.3i (HT only) Be able to describe neutrality and relative acidity and alkalinity in terms of the effect of the concentration of hydrogen ions on the numerical value of pH (whole numbers only) and pH of titration curves.
C3.3j (HT only) Know that as hydrogen ion concentration increases by a factor of ten the pH value of a solution decreases by a factor of one.
C3.3k Be able to describe techniques and apparatus used to measure pH.
Decomposition of a liquid during the conduction of electricity is a chemical reaction called electrolysis. This section explores the electrolysis of various molten ionic liquids and aqueous ionic solutions. You should be familiar with ionic solutions and solids. Common misconceptions - ionic solutions conduct because they are able to use of the movement of electrons. Another common misconception is that ionic solids do not conduct electricity because electrons cannot move.
C3.4a Know that metals (or hydrogen) are formed at the cathode and non-metals are formed at the anode in electrolysis using inert electrodes and be familiar with the terms cations and anions
C3.4b predict the products of electrolysis of binary ionic compounds in the molten state compounds such as NaCl.
C3.4c Be able to describe competing reactions in the electrolysis of aqueous solutions of ionic compounds in terms of the different species present.
C3.4d Be able to describe electrolysis in terms of the ions present and reactions at the electrodes
C3.4e Be able to describe the technique of electrolysis using inert and non-inert electrodes.
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