Global challenges Study Guide

Recycling involves processing waste materials to create new products, often reducing the consumption of fresh raw materials, energy usage, air and water pollution, and greenhouse gas emissions. A specific type of recycling for a different use, sometimes called upcycling, focuses on transforming materials into something of higher value or quality than the original. This is viable when the discarded material still possesses desirable properties that can be repurposed, or when the cost and energy required for transformation are less than producing a new product from virgin resources. For example, plastic bottles can be melted down and reformed into new plastic materials for furniture or clothing, rather than simply being made back into bottles. This reduces the demand for new plastics, which are derived from finite fossil fuels. The process typically involves collection, sorting (to separate different material types and contaminants), cleaning, processing (e.g., shredding, melting, reforming), and then manufacturing the new product. The viability depends on several factors: the availability of the waste material, the cost and efficiency of processing, the market demand for the new product, and the environmental benefits achieved.

Organic chemistry focuses on compounds containing carbon atoms. A key skill in this area is understanding and drawing structural formulae, particularly fully displayed formulae, which show all atoms and bonds within a molecule. This objective covers the first four members of four important homologous series: alkanes, alkenes, alcohols, and carboxylic acids. Each series has a general formula and characteristic functional groups that determine their chemical properties.

Alkanes are saturated hydrocarbons, meaning they contain only single carbon-carbon bonds. Their general formula is CnH2n+2. The first four members are methane, ethane, propane, and butane.

Alkenes are unsaturated hydrocarbons with at least one carbon-carbon double bond. Their general formula is CnH2n (for cyclic alkenes or those with one double bond). The first four members (with one double bond) are ethene, propene, but-1-ene (or but-2-ene, indicating double bond position, although for these small molecules, positional isomers become more relevant for butene onwards).

Alcohols contain the hydroxyl (-OH) functional group. Their general formula is CnH2n+1OH. The first four members are methanol, ethanol, propanol, and butanol.

Carboxylic acids contain the carboxyl (-COOH) functional group. Their general formula is CnH2n+1COOH. The first four members are methanoic acid, ethanoic acid, propanoic acid, and butanoic acid.

When drawing fully displayed formulae, every atom (carbon, hydrogen, oxygen) and every bond (single, double) must be explicitly shown. This provides a complete picture of the molecule's structure and connectivity, which is crucial for understanding its reactions and properties. For example, in ethene, the double bond between the two carbon atoms is clearly depicted, along with the hydrogen atoms attached to each carbon. Similarly, in ethanol, the hydroxyl group (-OH) is shown bonded to one of the carbon atoms, with all H-C and O-H bonds drawn out.