Chemistry

Rationale/Aims

Chemistry is the study of materials and substances, and the transformations they undergo through interactions and the transfer of energy. Chemists can use an understanding of chemical structures and processes to adapt, control and manipulate systems to meet particular economic, environmental and social needs.

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Structure of Chemistry

In Chemistry, students develop their understanding of chemical systems, and how models of matter and energy transfers and transformations can be used to describe, explain and predict chemical structures, properties and reactions.

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Links to Foundation to Year 10

The Chemistry curriculum continues to develop student understanding and skills from across the three strands of the F-10 Australian Curriculum: Science. In the Science Understanding strand, the Chemistry curriculum draws on knowledge and understanding from across the four sub-strands of Biological, Physical, Chemical and Earth and Space Sciences.

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Representation of Cross-curriculum priorities

While the significance of the cross-curriculum priorities for Chemistry varies, there are opportunities for teachers to select contexts that incorporate the key concepts from each priority.

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Achievement standards

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Unit 2: Molecular interactions and reactions

Unit 2: Molecular interactions and reactions Description

In this unit, students develop their understanding of the physical and chemical properties of materials including gases, water and aqueous solutions, acids and bases. Students explore the characteristic properties of water that make it essential for physical, chemical and biological processes on Earth, including the properties of aqueous solutions. They investigate and explain the solubility of substances in water, and compare and analyse a range of solutions. They learn how rates of reaction can be measured and altered to meet particular needs, and use models of energy transfer and the structure of matter to explain and predict changes to rates of reaction. Students gain an understanding of how to control the rates of chemical reactions, including through the use of a range of catalysts.

Through the investigation of appropriate contexts, students explore how evidence from multiple disciplines and individuals and the development of ICT and other technologies have contributed to developing understanding of intermolecular forces and chemical reactions. They explore how scientific knowledge is used to offer reliable explanations and predictions, and the ways in which it interacts with social, economic, cultural and ethical factors.

Students use a range of practical and research inquiry skills to investigate chemical reactions, including the prediction and identification of products and the measurement of the rate of reaction. They investigate the behaviour of gases, and use the kinetic theory to predict the effects of changing temperature, volume and pressure in gaseous systems.


Unit 2: Molecular interactions and reactions Learning Outcomes

By the end of this unit, students:

  • understand how models of the shape and structure of molecules and intermolecular forces can be used to explain the properties of substances, including the solubility of substances in water
  • understand how kinetic theory can be used to explain the behaviour of gaseous systems, and how collision theory can be used to explain and predict the effect of varying conditions on the rate of reaction
  • understand how models and theories have developed based on evidence from multiple disciplines, and the uses and limitations of chemical knowledge in a range of contexts
  • use science inquiry skills to design, conduct, evaluate and communicate investigations into the properties and behaviour of gases, water, aqueous solutions and acids and the factors that affect the rate of chemical reactions
  • evaluate, with reference to empirical evidence, claims about chemical properties, structures and reactions
  • communicate, predict and explain chemical phenomena using qualitative and quantitative representations in appropriate modes and genres.

Unit 2: Molecular interactions and reactions Content Descriptions

Science Inquiry Skills (Chemistry Unit 2)

Identify, research, construct and refine questions for investigation; propose hypotheses; and predict possible outcomes (ACSCH040)

Design investigations, including the procedure/s to be followed, the materials required, and the type and amount of primary and/or secondary data to be collected; conduct risk assessments; and consider research ethics (ACSCH041)

Conduct investigations, including measuring pH and the rate of formation of products, identifying the products of reactions, and testing solubilities, safely, competently and methodically for the collection of valid and reliable data (ACSCH042)

Represent data in meaningful and useful ways, including using appropriate graphic representations and correct units and symbols; organise and process data to identify trends, patterns and relationships; identify sources of random and systematic error; identify anomalous data; estimate the effect of error on measured results; and select, synthesise and use evidence to make and justify conclusions (ACSCH043)

Interpret a range of scientific and media texts, and evaluate processes, claims and conclusions by considering the quality of available evidence; and use reasoning to construct scientific arguments (ACSCH044)

Select, construct and use appropriate representations, including physical and graphical models of molecules, energy profile diagrams, electron dot diagrams, ionic formulae, chemical formulae, chemical equations and phase descriptors for chemical species to communicate conceptual understanding, solve problems and make predictions (ACSCH045)

Select and use appropriate mathematical representations to solve problems and make predictions, including using the mole concept to calculate the mass of chemicals and/or volume of a gas (at standard temperature and pressure) involved in a chemical reaction, and using the relationship between the number of moles of solute, concentration and volume of a solution to calculate unknown values (ACSCH046)

Communicate to specific audiences and for specific purposes using appropriate language, nomenclature, genres and modes, including scientific reports (ACSCH047)

Science as a Human Endeavour (Units 1 and 2)

Science is a global enterprise that relies on clear communication, international conventions, peer review, and reproducibility (ACSCH048)

Development of complex models and/or theories often requires a wide range of evidence from multiple individuals and across disciplines (ACSCH049)

Advances in science understanding in one field can influence other areas of science, technology and engineering (ACSCH050)

The use of scientific knowledge is influenced by social, economic, cultural and ethical considerations (ACSCH051)

The use of scientific knowledge may have beneficial and/or harmful and/or unintended consequences (ACSCH052)

Scientific knowledge can enable scientists to offer valid explanations and make reliable predictions (ACSCH053)

Scientific knowledge can be used to develop and evaluate projected economic, social and environmental impacts and to design action for sustainability (ACSCH054)

Science Understanding

Intermolecular forces and gases

Examples in context

Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.

Analysing the structure of materials – forensic chemistry

Forensic science often relies on chemical processes to analyse materials in order to determine the identity, nature or source of the material (ACSCH052). This requires detailed knowledge of both chemical and physical properties of a range of substances as well as the structure of the materials. Analysis techniques include different forms of chromatography to determine the components of a mixture, for example analysis of urine samples to identify drugs or drug byproducts, identification of traces of explosives, or the presence of an unusual substance at a crime scene. Evidence from forensic analysis can be used to explain the nature and source of samples and predict events based on the combination of evidence from a range of sources (ACSCH053). Calculations of quantities, including the concentrations of solutions, are an essential part of forensic chemistry, as is consideration of the reliability of evidence and the accuracy of forensic tests.

Scuba diving and the behaviour of gases

Safe scuba diving requires knowledge of the behaviour of gases with reference to volume, pressure and temperature. In particular, divers should understand how the volume of a gas varies with the surrounding pressure, in order to prevent damage to their respiratory, circulatory and nervous system. Diving equipment is designed to reduce the risk of dealing with gases at high pressure, including both the choice of materials used and the design of systems to improve efficiency and safety (ACSCH052). Guidelines and regulations based on understanding of gas compression and expansion due to changes in water pressure enable divers to avoid conditions such as pulmonary barotrauma and decompression sickness (ACSCH053).

Development of VSEPR theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is based on an understanding of subatomic and molecular structure and is an extremely powerful tool in the prediction of the shapes of molecules. In 1940 Sidgwick and Powell proposed that the shapes of molecules are dependent on the number of valence electrons in atoms within molecules. This idea was developed further by Australian scientist Sydney Nyholm and Canadian Ronald Gillespie in 1957 to describe how electrostatic repulsion between bonding and/or non-bonding pairs of electrons can be used to reliably predict the shapes of molecules (ACSCH049). They were able to demonstrate a relationship between the internal electronic structure of molecules, as predicted by knowledge of chemical bonding, and the overall shape of the molecules, as revealed by methods such as and X-ray crystallography (ACSCH048). Two- and three-dimensional graphical models have been developed and adopted by chemists to represent and communicate the shapes of molecules (ACSCH048).

Observable properties, including vapour pressure, melting point, boiling point and solubility, can be explained by considering the nature and strength of intermolecular forces within a substance (ACSCH055)

The shapes of molecules can be explained and predicted using three-dimensional representations of electrons as charge clouds and using valence shell electron pair repulsion (VSEPR) theory (ACSCH056)

The polarity of molecules can be explained and predicted using knowledge of molecular shape, understanding of symmetry, and comparison of the electronegativity of elements (ACSCH057)

The shape and polarity of molecules can be used to explain and predict the nature and strength of intermolecular forces, including dispersion forces, dipole-dipole forces and hydrogen bonding (ACSCH058)

Data from chromatography techniques (for example, thin layer, gas and high-performance liquid chromatography) can be used to determine the composition and purity of substances; the separation of the components is caused by the variation of strength of the interactions between atoms, molecules or ions in the mobile and stationary phases (ACSCH059)

The behaviour of gases, including the qualitative relationships between pressure, temperature and volume, can be explained using kinetic theory (ACSCH060)

Aqueous solutions and acidity

Examples in context

Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.

Acid rain

Rain water is naturally acidic as a result of carbon dioxide dissolved in water and from volcanic emission of sulphur. However scientists have observed an ongoing increase in the acidity of rain and the reduction of the pH of the oceans, which has been explained by an increased release of acidic gases including carbon dioxide, nitrogen oxides and sulphur dioxide into the atmosphere (ACSCH053). Most sulphur dioxide released to the atmosphere comes from burning coal or oil in electric power stations. Scientists have used trends in data to predict that continued increases in acidic emissions will have adverse effects on aquatic systems, forests, soils, buildings, cultural objects and human health (ACSCH053). Concern over acid rain has led to the design of technical solutions such as flue-gas desulphurisation (FGD) to remove sulphur-containing gases from coal-fired power station stacks, and emissions controls such as exhaust gas recirculation to reduce nitrogen oxide emissions from vehicles (ACSCH054). A number of international treaties and emissions trading schemes also seek to lower acidic emissions.

Blood chemistry

Blood plasma is an aqueous solution containing a range of ionic and molecular substances. Maintenance of normal blood solute concentrations and pH levels is vital for our health. Changes in blood chemistry can be indicative of a range of conditions such as diabetes, which is indicated by changed sugar levels. Pathologists compare sample blood plasma concentrations to reference ranges that reflect the normal values found in the population and analyse variations to infer presence of disease (ACSCH050). Knowledge of blood solute concentration is used to design intravenous fluids at appropriate concentrations, and to design plasma expanders such as solutions of salts for treatment of severe blood loss (ACSCH052).

Water quality

The issue of security of drinking water supplies is extremely important in Australia and many parts of the Asia region. Scientists have developed regulations for safe levels of solutes in drinking water and chemists use a range of methods to monitor water supplies to ensure that these levels are adhered to. Water from different sources has differing ionic concentrations, for example, bore water has a high iron content. Knowledge of the composition of water from different sources informs decisions about how that water is treated and used (ACSCH052). Desalination plants have been built around Australia to meet the supply needs of drinking water. These have high energy requirements and can have unwanted environmental impacts where the water is extracted from the oceans. Scientific knowledge and experimental evidence informs international action aimed at addressing current and future issues around the supply of potable water (ACSCH054).

Water is a key substance in a range of chemical systems because of its unique properties, including its boiling point, density in solid and liquid phases, surface tension, and ability to act as a solvent (ACSCH061)

The unique properties of water can be explained by its molecular shape and hydrogen bonding between molecules (ACSCH062)

The concentration of a solution is defined as the amount of solute divided by the amount of solution; this can be represented in a variety of ways including by the number of moles of the solute per litre of solution (mol L-1) and the mass of the solute per litre of solution (g L-1) (ACSCH063)

The presence of specific ions in solutions can be identified using analytical techniques based on chemical reactions, including precipitation and acid-base reactions (ACSCH064)

The solubility of substances in water, including ionic and molecular substances, can be explained by the intermolecular forces between species in the substances and water molecules, and is affected by changes in temperature (ACSCH065)

The pH scale is used to compare the levels of acidity or alkalinity of aqueous solutions; the pH is dependent on the concentration of hydrogen ions in the solution (ACSCH066)

Patterns of the reactions of acids and bases (for example, reactions of acids with bases, metals and carbonates) allow products to be predicted from known reactants (ACSCH067)

Rates of chemical reactions

Examples in context

Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.

The importance of enzymes

Enzymes are specific to particular reactions and act as important catalysts in many biological reactions, including those involved in digestion and respiration. Evidence for the existence and action of enzymes initially arose from Louis Pasteur’s study of fermentation of sugar to form alcohol in the nineteenth century. Further work, involving a wide range of scientists, proposed that enzyme action was associated with protein molecules (ACSCH049). Catalysts work in a variety of ways, and knowledge of the structure of enzyme molecules helps scientists to explain and predict how they are able to lower the activation energy for reactions (ACSCH053). This work often relies on evidence from laboratory experiments as well as analytical methods used to determine the structure of molecules (ACSCH049). For example, Australian John Cornforth was awarded the Nobel Prize for chemistry for his study of the molecular geometry of enzymes and how they are able to catalyse essential biochemical reactions.

Cost of corrosion

Corrosion of metals can have significant negative economic, environmental and safety consequences. For example, corrosion of steel pipes led to the 2008 gas plant explosion on Varunus Island, Western Australia, cutting the state’s gas supply by 30%. Many heritage structures, particularly bridges, have significant corrosion issues that compromise user safety, such as corrosion of main cables on suspension bridges. Addressing these issues can be complex and costly, and decisions about maintenance or replacement often involve consideration of factors such as cost, aesthetic or cultural value, and safety (ACSCH052). Most contemporary methods of corrosion prevention rely on knowledge of chemical and electrochemical redox processes, including the use of graphene within varnish coatings of iron or steel. The extension of a metal’s useful life will achieve cost savings and improve environmental impacts for many Australian industries, where a significant amount of industry is located on the coast and/or relies on shipping for imports and exports (ACSCH054).

Development of collision theory

Collision theory enables chemists to explain and predict the rates of a vast range of chemical reactions in many different contexts (ACSCH053). German chemist Max Trautz published research about aspects of collision theory, in particular the significance of activation energy, in 1916. William Lewis, working independently in England at the same time, proposed complimentary work on collision theory in 1918 (ACSCH048). The First World War prevented not only the two chemists working together, but even being aware of each other’s work. Further work on collision theory enabled a quantitative approach to be taken which allowed for the prediction and control of chemical reaction rates; these understandings are now used by chemical engineers to design efficient, safe and economically viable industrial processes (ACSCH052).

Varying the conditions present during chemical reactions can affect the rate of the reaction and in some cases the identity of the products (ACSCH068)

The rate of chemical reactions can be quantified by measuring the rate of formation of products or the depletion of reactants (ACSCH069)

Collision theory can be used to explain and predict the effect of concentration, temperature, pressure and surface area on the rate of chemical reactions by considering the structure of the reactants and the energy of particles (ACSCH070)

The activation energy is the minimum energy required for a chemical reaction to occur and is related to the strength of the existing chemical bonds; the magnitude of the activation energy influences the rate of a chemical reaction (ACSCH071)

Energy profile diagrams can be used to represent the enthalpy changes and activation energy associated with a chemical reaction (ACSCH072)

Catalysts, including enzymes and metal nanoparticles, affect the rate of certain reactions by providing an alternative reaction pathway with a reduced activation energy, hence increasing the proportion of collisions that lead to a chemical change (ACSCH073)