What are Chemical Substances?

1.1 Particles in Solids, Liquids and Gases

recall the three states of matter and how they can be interconverted

Revise the grouping of different materials as solids, liquids and gases. Ask pupils how different states can be interconverted - ice/water/water vapour can be used as an example.

describe and draw the arrangement of particles in solids, liquids and gases

explain the general properties of solids, liquids and gases in terms of the arrangement and movement of particles

Relate properties such as shape, volume, ability to be poured (to flow), compressibility, to the behaviour of particles in solids, liquids and gases.

explain diffusion in terms of the movement of particles

Discuss examples of diffusion such as cooking smells, perfume, and explain in terms of the behaviour of particles

1.2 Atomic Structure

recall that an atom consists of a nucleus and electrons

Develop the concept of a nuclear atom, appreciating the relative sizes of an atom and its nucleus

describe the structure of an atom in terms of protons, neutrons and electrons

Discuss the nature of the nucleus.

state the relative mass and relative charge of a proton, a neutron and an electron

Explain relative mass and relative charge. Discuss the charges on protons and electrons and the implications for the atom. Explain that neutrons and protons account for almost all of the mass of the atom.

Understand that atoms of elements can be represented by symbols

understand the terms atomic number, and mass number

Define the terms atomic number, mass number. Discuss the idea that each element has its own unique atomic number. Describe an atom in symbol form ^A_ZX. Draw diagrams showing the structure of atoms.

give the electronic structures of the first twenty elements in the periodic table (a periodic table will be provided)

Discuss the arrangement of elements in the periodic table according to their atomic numbers. Discuss the idea of different energy levels/shells and the way electrons fill up these energy levels.

Understand the term relative atomic mass and explain the existence of isotopes

Consider that the relative atomic masses of some elements are not whole numbers, hence the existence of isotopes and their atomic structure. Discuss relative atomic mass as the average mass of the atoms of an element.

calculate the relative atomic mass of an element from relative masses and abundances of its isotopes

recall the formulae of elements and simple compounds in the syllabus

Discuss the idea that a formula shows the ratio of atoms of the elements in a substance.

calculate relative formula mass from relative atomic masses

1.3 Ionic and Covalent Bonding

describe the differences between elements, compounds and mixtures

Discuss and give definitions of elements, compounds and mixtures

understand that atoms of different elements can combine to form compounds by the formation of new chemical bonds

Describe compounds as substances in which atoms of different elements are chemically bonded together.

understand that chemical bonds can be made by the transfer or sharing of electrons

Discuss the fact that Group 0 elements are very unreactive and note their electronic structure. Point out that when elements combine, they (often) attain the electronic structure of atoms of elements in Group 0; this can be by gaining, losing or sharing electrons.

describe the formation of cations by electron loss and anions by electron gain

Consider compounds formed between Group 1 and Group 7 elements.

describe the formation of Na⁺ and Cl^- ions and hence the formation of other ions in other ionic compounds

Discuss the specific example of a sodium atom and a chlorine atom combining to form sodium chloride. Use the number of electrons and protons to calculate the charges on the ions and hence the formula of the compound NaCl. Other compounds (of metals/non-metals) can be worked out by ensuring that the ions have Group 0 electronic structures and the number of electrons lost by the metal atom(s) equals the number gained by the non-metal atom(s).

recall that electron sharing results in the formation of covalent bonds and this results in molecules (e.g. hydrogen)

Draw a diagram of a hydrogen molecule showing how electrons are shared; the covalent bond is the shared pair of electrons and the formula of the molecule is H₂.

explain, using dot-and-cross diagrams, the formation of simple covalent molecules including H₂, Cl₂, H₂O, HCl and CH₄ in terms of the electronic structures of their atoms

Describe how the atoms in these covalent molecules attain the electronic structure of an atom of an element in Group 0.

1.4 Properties of Ionic and Covalent Substances

describe the physical properties of a giant ionic structure like sodium chloride

Describe how positive and negative ions, held together by electrostatic forces, form a giant lattice. describe the resultant properties: MP, BP, density, solubility, electrical conductivity

explain the physical properties of a giant ionic structure like sodium chloride

Explain the resultant properties: MP, BP, density, solubility, electrical conductivity

recall that covalent bond formation can also result in giant structures (e.g. diamond and graphite)

Explain that some covalent substances have giant structures.

describe the physical properties of simple molecular substances

Describe the existence of small molecules. Describe their properties: MP, BP, density, solubility, electrical conductivity.

explain the physical properties of simple molecular substances. Describe and explain giant covalent structures (to include diamond and graphite)

Simple molecular substances only have weak forces between their molecules; hence deduce their properties: MP, BP, density, solubility, electrical conductivity. Describe the existence of large molecules. Giant covalent molecules have only strong covalent bonds; hence explain their different properties.

predict the type of structure of a substance from its physical properties

Summarise the key differences in the properties of ionic and simple molecular covalent substances: MP, BP, solubility, electrical conductivity when solid, liquid or in solution.

predict the type of structure of a substance from its physical properties

Summarise the properties of giant covalent molecular substances: (MP, BP, solubility, electrical conductivity when solid, liquid or in solution) and compare with simple molecular and ionic substances.

1.5 Reactions (Word and Symbol Equations)

represent chemical reactions by word equations

Discuss how, in a chemical reaction, new substances are formed (products) from the original substances (reactants): reactants ® products.

write balanced equations for the formation of oxides

Explain that, in a chemical reaction, the atoms in the reactants are rearranged to form the products; therefore, there must be the same number of atoms of each type on each side of the equation.

write balanced equations to describe and explain a wide range of reactions including ionic interactions

Write balanced equations for reactions in the syllabus. Extend to include ionic equations, in which charge must also be balanced

recall and use in equations, where appropriate, the state symbols (s), (l), (g) and (aq)

Recognise that state symbols represent the states of the reactants and products.

1.6 Mass Relation Calculations

determine the formulae of simple compounds from reacting masses and understand that these are empirical

Define the term 'empirical formula'; give a method for determining empirical formulae from reacting masses

use given chemical equations to calculate masses of reactants and products

Show the connection between masses of reactants and products and chemical equations.

1.7 Mole Calculations

convert moles into masses and vice versa

recall Avogadro's Law and use it to calculate volumes of gases in reactions, given the relevant equation

calculate the volume of a given mass of gas (given the molar volume at that temperature and pressure) and vice versa

calculate and inter-relate masses or volumes of substances involved in a reaction, given the relevant equation