Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.
The production of wine, along with that of many other food products, relies on the successful control of a range of reversible reactions in order to maintain the required chemical balance within the product. For wine, this balance includes the acidity, alcohol concentration, sugar levels and the colour of the wine. Techniques such as auto titration, gas chromatography and infrared spectroscopy are used to measure the chemical composition of wine. Data from these methods, including the analysis of multivariate data, has enabled scientists to identify how the concentrations of the various chemicals in the wine are related, both to each other and the observable properties of wine such as taste and aroma (ACSCH082). Sulphur dioxide is used to maintain chemical balance in wine, as it binds with acetaldehyde. ‘Sulphite calculators’ are available so that wine makers can predict the amount of sulphur dioxide required. However decisions as to how the sulphur dioxide is added to the wine, including how much to use, will depend on preferences of the winemaker, especially for those producers who market wine as ‘organic’ or ‘preservative free’ (ACSCH084).
The levels of carbon dioxide in the atmosphere have a significant influence on global systems, including surface temperatures. The oceans contribute to the maintenance of steady concentrations of atmospheric carbon dioxide because the gas can dissolve in seawater through a range of reversible processes. The uptake of anthropogenic carbon dioxide by the oceans is driven by the difference in gas pressure in the atmosphere and in the oceans, and by the air/sea transfer velocity. Because carbon dioxide is increasing in the atmosphere, more of it moves into the ocean to balance the oceanic and atmospheric gas pressures, causing a change in the equilibrium point. Dissolved carbon dioxide increases ocean acidity, which is predicted to have a range of negative consequences for ecosystems, including direct impacts on oceanic calcifying organisms such as corals, crustaceans and molluscs because structures made of calcium carbonate are vulnerable to dissolution under at lower pH levels (ACSCH088). The United Nations Kyoto Protocol and the establishment of the Intergovernmental Panel on Climate Change aim to secure global commitment to a significant reduction in greenhouse gas emissions over the next decades (ACSCH087).
Lavoisier, often referred to as the father of modern chemistry, believed that all acids contained oxygen. In 1810, Davy proposed that it was hydrogen, rather than oxygen, that was common to all acids (ACSCH083). Arrhenius linked the behaviour of acids to their ability to produce hydrogen ions in aqueous solution, however this theory only related to aqueous solutions and relied on all bases producing hydroxide ions. In 1923 Brønsted (and at about the same time, Lowry) refined the earlier theories by describing acids as proton donators (ACSCH083). This theory allowed for the description of conjugate acid-bases, and for the explanation of the varying strength of acids based on the stability of the ions produced when acids ionise to form the hydrogen ions. This concept has been applied to contemporary research into ‘superacids’, such as carborane acids, which have been found to be a million times stronger than sulphuric acid when the position of equilibrium in aqueous solution is considered.