5.10 (sheet a) Using resources Ceramics Non-metallic solids High melting points Not made form carbon based compounds Excellent insulators (of heat and electricity) Very brittle and stiff There are two main types of ceramics: Clay ceramics Clay is a soft material that is taken from the earth. When it is fired it becomes a hard clay ceramic. Because it can be moulded then hardened, it is a very useful substance. Glass Glass can be moulded when hot and then cooled to form many shapes. Most glass is soda-lime glass. This is made by heating a mixture of limestone, sand and sodium carbonate until it melts; this cools as glass. Borosilicate is a different type of glass with a higher melting point. It is made in the same way but is a mixture of sand and boron trioxide. Corrosion Corrosion is when a metal is gradually destroyed by reacting with substances in the environment. Rust is a type of corrosion: Iron + oxygen + water  hydrated iron (III) oxide Rust is flaky and soft. Objects, such as bridges, made from iron that have rusted will not be a strong as they were when new. Aluminium also corrodes when exposed to air however the layer of aluminium oxide that forms actually protects the aluminium metal underneath. Preventing corrosion Stopping corrosion is important. Structures such as bridges need to remain strong or they may become dangerous to use. Corrosion can be prevented in a number of ways. Creating a barrier – Painting a metal or coating it with plastic keeps out water and oxygen. Electroplating is where metals are coated with a different metal. Oiling or greasing is used where moving parts need protecting. Sacrificial method – placing a more reactive metal with the metal you want to protect. For example, big blocks of magnesium can be bolted to steel bridges. Other methods – galvanising is a combination of a barrier and a sacrificial metal. Zinc is sprayed onto iron. If the zinc is scratched, the zinc acts as a sacrificial metal. Composites Composites are made of one material embedded in another. The embedded material is usually there to give extra strength (as reinforcement). Concrete is a composite of sand and cement Carbon fibre is a commonly used composite material. Wood and fibre glass are also composite materials. 5.10 (sheet a) Using resources Polymers When monomers (very small molecules) join together a polymer (a very large molecule) is formed. The atoms in polymers are held together by strong covalent bonds. Polymers are flexible, tough and are easily moulded. The properties of the polymer depends on two things: What it is made from (the monomers) How it was made (the reaction conditions) Metals Malleable Good conductors (heat and electricity) Ductile (can be drawn into wires) Shiny Stiff Alloys A mixture of two or more metals. The properties of the alloy depends on the metals that are mixed. The layers of atoms in alloy metals do not slide as easily. This changes the properties. Types of alloys Alloys of iron Pure iron is too soft and bendy for most uses. Iron is frequently used to make an alloy called steel. Gold alloys Pure gold is too soft to be worn everyday as jewellery. Gold alloys contain other metals such as silver, copper and zinc; this hardens the gold alloy but means the decorative colour is maintained or enhanced. Pure gold is described as 24 carat. Aluminium alloys Aluminium has a low density but is soft. Aluminium alloys are made in the manufacture of aircrafts because they are still low denslty but are stronger. Common alloys: Bronze - An alloy of copper and tin. Harder than copper but still a decorative colour. Good for statues and medals. Brass – An alloy of copper and zinc. Has a gold like appearance. More malleable than bronze. Good for moving parts. Used for water taps and door fittings. Thermosetting polymers: have cross links between the polymer chains. These polymers char and do not melt. Good for electrical sockets etc. Thermosoftening polymers: can be metled and reformed into new shapes. Good for throw away items such as bottles as they can be recycled easily.

5.10 (sheet b) Using resources Resources and sustainability Natural resources form without human input. We have relied on them for hundreds of thousands of years, and now many of them are running out. We have replaced many natural resources with synthetic (man made) alternatives however many of these synthetic alternatives still rely on natural resources as the raw materials. For example, we have replaced tree sap with fossil fuels in the production of rubber, however fossil fuels are a finite (non-renewable) resource. We enhance the production of natural resources using agriculture. The development of fertiliser greatly enhanced our ability to do this. Renewable and non-renewable Some resources are renewable(will never run out because they are replaced as quickly as we use them) and some are non-renewable or finite (there is a limited amount as they do not form quickly enough to replace what we use). Examples: Renewable – timber Non-renewable – fossil fuels and nuclear fuels Sustainable development This is an approach to development that takes account of the needs of present society while not damaging the live of future generations. We can’t stop using finite resources all together but chemistry gives us ways to reduce the amount we use and therefore reduce the damage we cause to the environment. Sustainability of copper (HT) There is a high demand for copper but the supply is limited. To increase the supply, chemists work on ways to extract copper from low grade ores (ores where previously it wouldn’t be financially worth extracting the tiny amount of copper present). Bioleaching: This uses bacteria to convert copper compounds in the ores into soluble copper compounds. The leachate (the solution created) contains copper ions which can be extracted using electrolysis or displacement reactions. Phytomining: This involves growing plants in soil that contains copper. The copper builds up in the plants system. When the concentration in the plant is high enough, the plant is harvested and the copper extracted. The copper compounds are then purified using electrolysis or displacement reactions. Both of these methods are efficient, cause little damage to the environment and ensure that copper remains available into the future. These methods are slower than traditional mining methods. 5.10 (sheet b) Using resources The Haber process The following conditions are used: Temperature: 450°C Pressure: 200 atmospheres Catalyst: iron The ammonia is then used in the production of fertilisers. Potable water Potable water is water that has been treated by humans or is naturally safe to drink. Potable water can come from a fresh water source (lakes, rivers and reservoirs) or sea water. Fresh water is filtered then sterilised. Sea water is desalinated via distillation or reverse osmosis. Reuse and recycling Reuse – using a product more than once Recycling – using waste materials to make new products. Reasons to recycle metals: Recycling metal uses a small fraction of the energy used to mine and extract new metal Energy isn’t cheap so this saves money There is a finite amount of each metal on earth Recycling cuts down on landfill. NPK FERTILISERS The three main essential elements needed by plants are: Nitrogen (to make protein) Phosphorus Potassium Every time a crop is grown in a field, these are used up by the plants. Every year, these elements must be replaced; farmers use NPK fertilisers to replace them. The ammonia produced by the Haber process is the source of nitrogen. Potassium and phosphorus are obtained from mined potassium chloride and potassium sulphate. Waste water treatment Waste water comes from: Baths and showers Toilets Washing up Agriculture This water is far too precious to waste so it is treated and put back into fresh water sources. Stages of treatment: Screening – removes the large bits Sedimentation – suspended solids settle and are removed Aerobic digestion – air is pumped in to help bacteria break down organic material aerobically Anaerobic digestion – the sludge is removed and broken down anaerobically producing methane (which can be used as a fuel) and digested waste that can be used as a fertiliser. Life cycle assessment Life cycle assessments (LCAs) assess the environmental impact of the entire lifetime of a product. This allows manufacturers and developers the information needed to make decisions on which product will have the least environmental impact.