Chemistry- Year 10, Unit 1

Everything to do with Chemistry

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Copper, Aluminium and Titanium

Copper- Copper is useful for electrical wiring and plumbing but natural supplies of ores containing large quantities of copper are limited. If we continue to use them they will run out completely.

Aluminium- Aluminium is resistant to corrosion. A reaction between the aluminium and oxygen from the air produces a 'thin' skin which prevents further corrosion. It is for this reason that greenhouses don't have to be painted. However, for some uses of aluminium, a thinker layer of this protective oxide is needed.

Aluminium has a low density so it is very light. It is used for...

·         drink cans

·         window framed

·         lightweight vehicles

·         aeroplanes

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Titanium- Titanium is strong and resistant to corrosion. It is used in...

·         aeroplanes

·         nuclear reactors

·         replacement hip joints

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Crude Oil and Fraction Distillation

Crude Oil- Crude oil is a mixture of compounds, most of which are molecules made up of carbon and hydrogen atoms only, called hydrocarbons. These hydrocarbon molecules vary in size. This affects their properties and how they are used as fuels. The larger the hydrocarbon (the greater the number of carbon and hydrogen atoms in a molecule)...

·         the less easily it flows, i.e. the viscous it is

·         the less easily it ignites, i.e. the less flammable it is

·         the less volatile it is, i.e. it doesn't vaporise as easily

·         the higher its boiling point

A mixture consists of two or more elements or compounds which are not chemically combined together, so the properties of the substances in the mixture remain unchanged and specific to that substance. This makes it possible to separate the substances in a mixture by physical methods such as distillation.

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Alkanes and Burning Fuels

Alkanes (Saturated Hydrocarbons)- The 'spine' of a hydrocarbon is made up of a chain of carbon atoms. When these are joined tohether by single carbon carbon bonds we say the hydrocarbon is saturated and it is known as an alkane. To put it simply...

·       hydrogen atoms can make 1 bond each

·       carbon atoms can make 4 bonds each

·       the simplest alkane, methane, is made up of 4 hydrogen atoms and 1 carbon atom.

The general formula for alkanes is C(n)H(2n+2).

In alkanes, all the carbon atoms are linked to 4 other atoms by single bonds. This means that all their bonds are 'occupied' (the alkane is saturated) so they are fairly nonreactive, although they do burn well. The shorter-chain hydrocarbons release energy more quickly by burning, so there is a greater demand for them as fuels.

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Burning Fuels- As fuels burn they produce waste products, which are then released into the atmosphere. The waste products produced depend on which elements are present in the fuel. Most fuels contain carbon and hydrogen, but many also contain some sulfur.

·         Carbon (C) > burn > Carbon dioxide + Carbon monoxide

·         Hydrogen (H) > burn > Water vapour (H(2)O)

·         Sulfur (S) > burn > Sulfur dioxide (SO(2))

-CO causes 'global warming' due to the Greenhouse effect                                                                   -SO(2) causes acid rain. Removing the sulfur before burning, or removing the waste gases, can reduce this. However, both of these add to the cost.

Power stations remove sulfer dioxide from the waste gases produced when combustion takes place to reduce the pollution they give out. Particles may also be released, which causes global dimming (a reduction in the amount of sunlight reaching the Earth's surface).

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Cracking Hydrocarbons, Making Alcohol from Ethene

Cracking Hydrocarbons- Longer-chain hydrocarbons can be cracked or broken down into shorter chains, which release energy more quickly by burning.

Hydrocarbons are cracked by heating them until they vaporise, then passing the vapour over a heated catalyst, where a thermal decomposition reaction takes place.

The products of cracking include alkanes and unsaturated hydrocarbons called alkenes. Some of the products are useful as fuels.

Making Alcohol from Ethene- Ethanol is an alcohol. It can be produced by reacting steam with ethene at a moderately high temperature and pressure in the presence of a catalyst, phosphoric acid. Ethanol can be used as a... solvent, fuel and component in alcoholic drinks.

Ethene + Steam > phosphoric acid > Ethanol

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Polymerisation-  Because all alkenes are unsaturated (have a double bond), they are very reactive. When small alkene molecules (monomers) join together to form long-chain molecules (polymers) without producing another substance, it is called polymerisation.

The properties of polymers depend on what they are made from and the conditions under which they were made. The materials commonly called plastics are all synthetic polymers. They are produced commercially on a very large scale and have a wide range of properties and uses. Polymers and plastics were first discovered in about 1933.

The resulting long-chain molecule is a polymer - in this case poly(ethene), often called polythene. Poly(propene) can be made in a similar way.

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Polymers- Polymers have many useful applications and new uses are being developed.

·         Polymers and composites are widely used in medicine and dentistry.

·         Implantable materials are used for hard and soft tissue surgery, replacing and fusing damaged bone and cartilage.

·         Hard-wearing anti-bacterial dental cements, coatings and fillers have been produced.

·         Hydro gels can be used as wound dressings.

·         Silicone hydro gel contact lenses have been developed over the past few years. Research has shown that people who wear this type of contact lens have a 5% lower risk of developing severe eye infections.

·         They can be used to coat fabrics with a waterproof layer.

·         Smart materials, including shape memory polymers, are also increasingly more common.

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Polymers and Disposing of Plastics

Polyvinyl Chloride (PVC)- can be used to make waterproof items and drain pipes and can also be used as an electrical insulator.

Polystyrene- is used to make the casing for electrical appliances, and it can be expanded to make protective packaging.

Poly(ethene)- is commonly used to make plastic bags and bottles.

Poly(propene)- can be used to make crates and ropes.

                                                                                                                             Disposing of Plastics- Because plastic is such a versitile material and it is cheap and easy to produce we tend to generate a large amount of plastic waste. There are various ways of disposing of plastics, unfortunately some of them have an impact on the environment.

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Landfill sites- The problem with most plastics is that they are non-biodegradable. Microorganisms have no effect on them, so they will not decompose and rot away. The use of landfill sites means that plastic waste builds up. However, research is being carried out on the development of biodegradable plastics.

Burning- Burning plastics produces air pollution. The production of carbon dioxide contributes to the Greenhouse effect which results in global warming. Some plastics cannot be burned at all because they produce toxic fumes.

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