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