Topic 1.1: Stoichiometric relationship – Introduction to the particulate nature of matter and chemical change
Physical and chemical properties depend on the ways in which different atoms combine.
• Understanding: Atoms of different elements combine in fixed ratios to form compounds, which have different properties from
their component elements.
▪ Elements: collection of atoms that has the same atomic number (e.g. O2, but not H2O)
▪ Compounds: formed when two or more elements bond together (e.g. H2O, but not O2)
▪ Compounds combine in fixed ratios of atoms (e.g. water (H2O) has a ratio of two hydrogen atoms to one oxygen atom)
▪ Compounds and their component elements have different properties (e.g. hydrogen gas (H2) and oxygen (O2) has different
properties from water (H2O))
• Understanding: Mixtures contain more than one element and/or compound that are not chemically bonded together and so retain
their individual properties.
▪ Mixture: combination of elements and/or compounds that are not chemically bonded together (e.g. H2O and NaCl)
▪ Pure substance: matter that has constant composition (e.g. H2O)
▪ Chemicals in mixtures retain their individual properties: pure substance can be separated using physical techniques (e.g. boiling;
when salt water is boiled, water evaporates leaving salt)
• Understanding: Mixtures are either homogeneous or heterogeneous.
▪ Homogeneous: mixture with uniform composition and uniform properties throughout (e.g. salt water, milk)
▪ Heterogeneous: : mixture with non-uniform composition and non-uniform properties throughout (e.g. soil, blood)
• Applications and skills: Deduction of chemical equations when reactants and products are specified.
▪ Law of conservation of mass: the type and number of atoms in the reactants must equal to those in the products
• Each side of the chemical equation therefore must be balanced
• Only coefficients can change; subscripts cannot change (e.g. 3O2; 3 can change, 2 cannot)
▪ Types of reaction
• Combination (synthesis): reaction involving the combination of two or more reactant to produce a single product
▪ Example: C (s) + O2 (g) → CO2 (g)
• Decomposition: reaction involving a single reactant being broken down into two or more products
▪ Example: CaCO3 (s) → + CaO (s) + CO2 (g)
• Single replacement: reaction occurring when one element replaces another in a compound
▪ Example: Mg (s) + 2HCl (aq) → MgCl2(aq) + H2 (g) (redox)
• Double replacement (metathesis): occur between ions to form insoluble substance and weak electrolytes
▪ Example: HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) (acid-base)
• Applications and skills: Application of the state symbols (s), (l), (g) and (aq) in equations.
▪ Solid (s) – has regular arrangement of particles with minimal movement between
them (e.g. H2O is ice under 0°C)
▪ Liquid (l) – has close arrangement of particles with free movement between them
(e.g. H2O is water above 0°C and under 100°C)
▪ Gas (g) – has random arrangement of particles with no intermolecular forces
between them (e.g. H2O is gas above 100°C)
▪ Aqueous (aq) – polar or ionic particles dissolved in water (e.g. NaCl in H2O)
• Applications and skills: Explanation of observable changes in physical
properties and temperature during changes of state.
▪ Horizontal movement: during a change in state (in a temperature
threshold) temperature does not increase as all energy is being used to
disrupt the attractive forces between the particles
▪ Vertical movement: the temperature increases in a certain state
• Nature of science: Making quantitative measurements with replicates to ensure
reliability—definite and multiple proportions.
• International-mindedness: Chemical symbols and equations are international, enabling effective communication amongst scientists
without need for translation.
• International-mindedness: (International Union of Pure and Applied Chemistry) is the world authority in developing standardized
nomenclature for both organic and inorganic compounds.
• Utilization: Refrigeration and how it is related to the changes of states and freeze-drying of foods. Atom economy.
• Guidance: Balancing of equations should include a variety of types of reactions.
• Guidance: Names of the changes of state—melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and
deposition—should be covered.
• Guidance: The term “latent heat” is not required.
• Guidance: Names and symbols of elements are in the data booklet in section
Physical and chemical properties depend on the ways in which different atoms combine.
• Understanding: Atoms of different elements combine in fixed ratios to form compounds, which have different properties from
their component elements.
▪ Elements: collection of atoms that has the same atomic number (e.g. O2, but not H2O)
▪ Compounds: formed when two or more elements bond together (e.g. H2O, but not O2)
▪ Compounds combine in fixed ratios of atoms (e.g. water (H2O) has a ratio of two hydrogen atoms to one oxygen atom)
▪ Compounds and their component elements have different properties (e.g. hydrogen gas (H2) and oxygen (O2) has different
properties from water (H2O))
• Understanding: Mixtures contain more than one element and/or compound that are not chemically bonded together and so retain
their individual properties.
▪ Mixture: combination of elements and/or compounds that are not chemically bonded together (e.g. H2O and NaCl)
▪ Pure substance: matter that has constant composition (e.g. H2O)
▪ Chemicals in mixtures retain their individual properties: pure substance can be separated using physical techniques (e.g. boiling;
when salt water is boiled, water evaporates leaving salt)
• Understanding: Mixtures are either homogeneous or heterogeneous.
▪ Homogeneous: mixture with uniform composition and uniform properties throughout (e.g. salt water, milk)
▪ Heterogeneous: : mixture with non-uniform composition and non-uniform properties throughout (e.g. soil, blood)
• Applications and skills: Deduction of chemical equations when reactants and products are specified.
▪ Law of conservation of mass: the type and number of atoms in the reactants must equal to those in the products
• Each side of the chemical equation therefore must be balanced
• Only coefficients can change; subscripts cannot change (e.g. 3O2; 3 can change, 2 cannot)
▪ Types of reaction
• Combination (synthesis): reaction involving the combination of two or more reactant to produce a single product
▪ Example: C (s) + O2 (g) → CO2 (g)
• Decomposition: reaction involving a single reactant being broken down into two or more products
▪ Example: CaCO3 (s) → + CaO (s) + CO2 (g)
• Single replacement: reaction occurring when one element replaces another in a compound
▪ Example: Mg (s) + 2HCl (aq) → MgCl2(aq) + H2 (g) (redox)
• Double replacement (metathesis): occur between ions to form insoluble substance and weak electrolytes
▪ Example: HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) (acid-base)
• Applications and skills: Application of the state symbols (s), (l), (g) and (aq) in equations.
▪ Solid (s) – has regular arrangement of particles with minimal movement between
them (e.g. H2O is ice under 0°C)
▪ Liquid (l) – has close arrangement of particles with free movement between them
(e.g. H2O is water above 0°C and under 100°C)
▪ Gas (g) – has random arrangement of particles with no intermolecular forces
between them (e.g. H2O is gas above 100°C)
▪ Aqueous (aq) – polar or ionic particles dissolved in water (e.g. NaCl in H2O)
• Applications and skills: Explanation of observable changes in physical
properties and temperature during changes of state.
▪ Horizontal movement: during a change in state (in a temperature
threshold) temperature does not increase as all energy is being used to
disrupt the attractive forces between the particles
▪ Vertical movement: the temperature increases in a certain state
• Nature of science: Making quantitative measurements with replicates to ensure
reliability—definite and multiple proportions.
• International-mindedness: Chemical symbols and equations are international, enabling effective communication amongst scientists
without need for translation.
• International-mindedness: (International Union of Pure and Applied Chemistry) is the world authority in developing standardized
nomenclature for both organic and inorganic compounds.
• Utilization: Refrigeration and how it is related to the changes of states and freeze-drying of foods. Atom economy.
• Guidance: Balancing of equations should include a variety of types of reactions.
• Guidance: Names of the changes of state—melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and
deposition—should be covered.
• Guidance: The term “latent heat” is not required.
• Guidance: Names and symbols of elements are in the data booklet in section
