Unit 2 Everyday Chemistry

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Metals

Finding Metals Most metals are found combined with other elements. These compounds are called ores. Some metals, including gold, silver and copper, are found uncombined in the Earth's crust. This means that we can find the element on its own.

Extracting Metals We get some metals, including iron, from their ores by heating the ore with carbon.

We get some metals, including aluminium, from their ores using electricity.

Using Metals The properties of metals are the things it can do and the way it acts. Metals are chosen for certain uses because of their properties.

Density of a metal is a measure of how heavy it is, compared to its volume. That is why lead weights are used for fishing lines.

All metals are good conductors of heat i.e. they have a high thermal conductivity. That is why metals are used for making pots and pans, radiators etc.

All metals are good conductors of electricity i.e. they have a high electrical conductivity. That is why metals are used for making electrical wiring etc.

Metals are malleable. This means that they are easily made into new shapes. This property is used when metals are made into a variety of objects, such as fencing, horse shoes etc.

Metals are strong. Metals are used to make many things because of this strength e.g. car bodies, girders, tools etc.

Alloys An alloy is a mixture of metals, or of metals with non-metals. Many alloys have important uses. Examples of alloys are: brass solder 'stainless' steel

Reactions of Metals Metals react with many different materials. By comparing reactions and seeing the differences between them we can recognise the reactivity of different metals.

Metals react with oxygen to produce metal oxides. Magnesium + Oxygen  Magnesium oxide Aluminium + Oxygen  Aluminium oxide

Some metals react with water to produce hydrogen. Sodium + Water  Sodium hydroxide + Hydrogen Potassium + Water  Potassium hydroxide + Hydrogen

Many metals react with dilute acid to produce hydrogen. Some metals, including copper, silver and gold, do not react with dilute acid. Zinc + Hydrochloric acid  Zinc chloride + Hydrogen Iron + Sulphuric acid  Iron sulphate + Hydrogen

Test for hydrogen The test for hydrogen is that it burns with a 'pop'.

Corrosion Corrosion is a chemical reaction. In corrosion the surface of a metal changing from an element to a compound. For corrosion to take place the metal must react with something in its surroundings.

Rusting Rusting is the corrosion of iron. Rusting results the iron object becoming weaker. Both oxygen (from the air) and water are required for rusting. Rust indicator can be used to show the extent of the rusting process.

Acid rain increases the rate of corrosion. Salt spread on roads increases the rate of corrosion on car bodywork.

Preventing Corrosion Physical protection prevents corrosion by making a surface barrier to air and water. Now the metal cannot corrode because air and/or water cannot get at the metal.

Physical protection Physical protection can be provided by: Painting Greasing Electroplating Galvanising Tin-plating Coating with plastic

Chemical protection prevents corrosion by using chemicals. Air and water can still get at the metal, but the chemicals prevent corrosion taking place.

Chemical protection Chemical protection can be provided by: Iron does not rust when attached to more reactive metals so zinc (galvanising) and scrap magnesium are used to protect iron. Anodising is a process which increases the thickness of the oxide layer on aluminium to provide protection against corrosion.

Batteries In a battery, electricity comes from a chemical reaction. Batteries require to be replaced due to the chemicals being used up in the reaction. Examples of rechargeable batteries include the lead-acid battery and the nickel-cadmium battery.

Cells Electricity can be produced by connecting different metals together, with a solution containing ions, to form a cell. The ion solution completes the circuit. The voltage between different pairs of metals varies. The size of the voltage depends on the difference in reactivity of the metals.

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Personal Needs

Keeping clean When cleaning hair, skin and clothes the main problem is oil and grease. This is because oil and grease do not dissolve in water.

Cleaning chemicals are required to break up the oil and grease into tiny droplets These droplets can then mix with water This happens because cleaning chemicals dissolve in both water and oil and grease.

Some manufactured products contain cleaning chemicals. Some are : Soaps Detergents Shampoos Washing-up liquids and powders.

Some soaps form a scum with hard water. Soapless detergents are used to form a lather with hard water. Dry-cleaning uses special solvents which are particularly good at dissolving oil and grease stains.

Clothing Clothing fabrics are made from thin strands called fibres. Fibres are made up of long chain molecules called polymers.

Natural fibres come from plants and animals. Some natural fibres are: silk wool cotton

Synthetic fibres are made by the chemical industry. Some synthetic fibres are Nylon Polyesters (e.g. Terylene)

Synthetic fibres can be used to make fabrics which have particular uses. Dyes are coloured compounds, which are used to give bright colours to clothing.

Chemists have developed ways of treating fabrics to improve their properties. Some fibres form strong bonds with water molecules These fibres are hard to drip-dry but they do not feel 'sweaty' to wear because they soak-up perspiration.

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Fuels

Fire A fuel is a chemical, which is burned to produce energy. When a substance burns it reacts with oxygen. Combustion is another word for burning.

A fire needs: Fuel Oxygen (usually from the air) A temperature high enough to start the fire and keep it going Take away anyone of the three and the fire goes out.

Putting out fire Fire-fighting methods in the lab and the home include using Fire blanket Sand Water Carbon dioxide gas Foam.

Different methods of putting out the fire are used in different situations. Water must not be used with oil, petrol and electrical fires.

Fossil fuels Fossil fuels are formed from animal and plant remains over a very long period of time. Fossil fuels include Coal Natural gas Oil Peat.

Finite Resources Fossil fuels are finite resources, i.e. they cannot be replaced. If we use too much of the fossil fuels a fuel crisis will result, when most of the fossil fuels have been used up.

Hydrocarbons The compounds, which are found in fossil fuels are mainly hydrocarbons. A hydrocarbon is a compound which contains hydrogen and carbon only. Hydrocarbons burn in a plentiful supply of air to produce carbon dioxide and water. Hydrocarbon + Oxygen  Carbon Dioxide + Water

Renewable resources Renewable resources are energy resources which can be replaced. Some renewable sources of energy are: Methane Ethanol Hydrogen

Methane is found in biogas, which is made by the breaking down of waste plant material. Ethanol is made from sugar cane and can be mixed with petrol to make a fuel for cars, Hydrogen, which can be made from water, is a likely fuel for the future.

Fractional Distillation Crude oil is a mixture of hydrocarbons. A fraction is a group of hydrocarbons with boiling points within a given range.

Fractional distillation is the process which separates crude oil into different fractions according to their boiling points.

Fractions Hydrocarbons made of small molecules boil more easily than hydrocarbons made of large molecules. Different fractions are used as different fuels.

The uses of the fractions is decided by their properties. How easy it is to make them turn into a gas (evaporate) Their thickness (viscosity) How easy they are to burn (flammability) Their boiling point range

Cracking Fractional distillation of crude oil gives more long chain hydrocarbons than are needed. Cracking is an industrial method for producing a mixture of smaller, more useful molecules.

Water Pollution Oil spillages can cause great damage to marine life and the environment.

Air Pollution Soot (carbon) and carbon monoxide, a poisonous gas, can be produced when hydrocarbons burn in a low supply of oxygen. The burning of some fuels releases sulphur dioxide, a poisonous gas, into the atmosphere.

Nitrogen and oxygen from the air can react inside a car engine to form nitrogen dioxide which is a poisonous gas. Lead compounds which used to be added to petrol cause pollution. Benzene fumes in unleaded petrol are toxic.

Soot particles, produced when diesel fuel does not burn properly, are harmful. Air pollution from the burning of hydrocarbons can be reduced by the use of catalytic converters which convert the pollutant gases to harmless gases.

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Plastics

Plastics are synthetic materials, i.e. made by the chemical industry. Most plastics are made from oil. Examples of plastics include polythene, polystyrene, perspex, PVC, nylon, Kevlar, bakelite, formica and silicones. The properties of plastic help to decide what they are used for.

Advantages and disadvantages of plastics For some uses, plastics have advantages over natural materials and vice versa. Biodegradable materials are broken down by bacteria in the soil and rot away.

Most plastics are not biodegradable and their durability and lightness can cause environmental problems. Some degradable plastics have been developed by chemists to ease the problems of plastic waste.

Disposing of plastics Some plastics burn or smoulder to give off toxic fumes, including carbon monoxide. We can get rid of plastics by burning, recycling and burying. With burning the heat produced can be used as a source of energy but there are problems with gases given off.

Recycling plastics Since oil is a finite resource, recycling is to be encouraged and chemists are looking for renewable sources of plastics. Recycling can be difficult because of the many different kinds of plastic in common use.

Different plastics Plastics can be either thermoplastic or thermosetting. A thermoplastic is one which can be reshaped on heating. A thermosetting plastic cannot be reshaped by heating. The uses of thermosetting plastics are decided by their heat and electrical insulation properties.

Making plastics Plastics are made up of polymers. These are very long molecules, made by joining together many small molecules.

Polymer molecules are made from many small molecules called monomers. The process of making a polymer by joining many monomers together is called polymerisation. Ethene monomers form poly(ethene), also called polythene; the styrene monomers form poly(styrene).

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