Chemistry- Products from rocks.
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- Created by: Jessica Cooper
- Created on: 13-04-13 12:13
Atoms
they have a small nucleus surrounded by electrons
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REMEBER
number of protons equals number of electrons
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Elements consist of one type of atom only
Atoms can have different numbers of protons, neutrons and electrons.It's the number of protons in the nucleus tat decides what type of atom it is
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Atoms can be represented by symbols
Atoms of each element can be represented by a one or two letter symbol
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The periodic table puts elements with similar properties together
The periodic table is laid out so that elements with similar properties form columns
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Balancing the equation
There must always be the same number of atoms of each element on both sides, they can't just disappear.
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Method to this
You balance just one type of atom at a time
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Limestone
It is mainly calcium carbonate
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Calcium oxide reacts with water to produce calcium hydroxide
Calcium hydroxide is an alkali which can be used to neutralise acidic soils in fields. Powdered limestone can be used for this to but the advantage of calcium hydroxide is that it works much faster
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Limestone is used to make other useful things too
Powdered limestone is heated in a kiln with powdered clay to make cement
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Quarrying limestone makes a right mess of the landscape
Digging limestone out of the ground can cause environmental problems
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Making stuff from limestone causes pollution too
Cement factories make a lot of dust, which can cause breathing problems
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But on the plus side
Limestone provides things that people want, like houses and roads and chemicals used in making dyes, paints and medicines also come from limestone
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Limestone products have advantages and disadvantages
Limestone is very quick and cheap way of constructing buildings, but concrete is said to be an unattractive building material
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Ores contain enough metal to make extraction worth while
A metal ore is a rock which contains enough metal to make it worthwhile extracting the metal from it.
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Metals are extracted from their ores chemically
A metal ore can be extracted chemically from it's metal ore by reduction.
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Some metals can be extracted by reduction with carbon
A metal can be extracted from it's ore chemically by reduction using carbon, when an ore is reduced, oxygen is removed from it. The ore is heated in a furnace and this is called smelting
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Some metals have to be extracted by electrolysis
Metals that are more reactive than carbon have to be extracted using electrolysis of molten compounds
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Copper is purified by electrolysis
Copper can be easily extracted by reduction with carbon. But copper produced this way is impure and impure copper doesn't conduct electricity very well. This doesn't help due to copper being mainly used for electrical wire.
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Electrolysis is the breaking down of a substance using electricity
It requires a liquid to conduct the electricity, called the electolyte
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More reactive metals react more vigorously than less reactive metals.
If you put a reactive metal into a solution of a dissolved metal compound, the reactive metal will replace the less reactive metal in the compound
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Copper-rich ores are in short supply
The supply of copper rich ores is limited, so it's important to recycle as much copper as possible.
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Metal extraction can be bad for the environment
Metal extraction uses a lot of energy and is bad for the environment. this is why we need to recycle
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Recycling metals is important
Mining and extracting metals takes lots of energy. Recycling metals only uses a small fraction of the energy needed to mine and extract new metal.E.G recycling copper only takes 15% of the energy that's needed to mine and extract new copper.
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Metals are strong and bendy and they're great conductors
All metals have some fairly similar properties-Metals are strong (hard to break), but they can be bent or hammered into different shapes. Metals are also good at conducing heat and they conduct electricity well
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Metals are good but not perfect
Metals are very useful structural materials, but some corrode when exposed to air and water, they are protected by being painted. But when they do corrode they lose there strength and hardness.
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A metal's exact properties decide how it's used
For example aluminium is corrosion resistant and has a low density. Pure aluminium isn't particularly strong, but it forms hard strong alloys
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Alloys are harder than pure metals
Different elements have different sized atoms. So when an element such as carbon is added to pure iron, the smaller carbon atom will upset the layers of pure iron atoms, making it more difficult for them to slide over each other. So alloys are harder
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Crude oil is a mixture of hydrocarbons
A mixture consists of two (or more) elements or compounds that aren't chemically bonded to each other. So crude oil is a mixture of many different compounds, most of the compounds are hydrocarbon molecules
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Crude oil is split into separate groups of hydrocarbons
The fractionating column works continuously, with heated crude oil piped in at the bottom. The vaporised oil rises up the column and the various fractions are constantly tapped off at the different levels where they condense
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Crude oil is mostly alkanes
All the fractions of crude oil are hydrocarbons called alkanes. Alkanes are made up of chains of carbon atoms surrounded by hydrogen atoms
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The shorter the molecules, the more runny the hydrocarbon is, that is the less viscous (gloopy) it is
The shorter the molecules, the more volatile they are. "More volatile" means they turn into gas at a lower temperature. So, the shorter the molecules, the lower the temperature at which that fraction vaporises or condenses & the lower boiling point
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Also ....
The shorter the molecules, the more flammable (easier to ignite) the hydrocarbon is
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The uses of hydrocarbons depend on their properties
E.g the petrol fraction has longer molecules, so it has a higher boiling point. Petrol is a liquid which is ideal for storing in the fuel tank of a car. It can flow to the engine were it's easily vaporised to mix with the air before it's egnited
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Crude oil provides an important fuel for modern life
Crude oil fractions burn cleanly so they make good fuels. Most modern transport is fuelled by a crude oil fraction e.g.cars & planes. Parts of crude oil are also burned in central heating systems in homes and in power stations to generate electricity
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Crude oil might run out one day!
Most scientists think that oil will run out, it is a non-renewable fuel. New oil reserves are discovered from time to time and technology is constantly improving, so it's now possible to extract oil that was once too difficult or expensive to extract
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Crude oil is not the environment's best friend
Oil spills can occur when the oil is being transported by tanker, this is bad for the local environment.Birds get covered in the stuff and are poisoned as they try to clean themselves. Other creatures, like sea otters and whales, are poisoned
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Burning fossil fuels releases gases and particles
Power stations burn huge amounts of fossil fuels to makulphur e electricity and cars are also a major culprit in burning fossil fuels
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Sulphur dioxide causes acid rain
When the sulphur dioxide mixes with clouds it forms dilute sulphuric acid. This then falls as acid rain.
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You can reduce acid rain by reducing sulphur emissions
One way to reduce acid rain is to simply reduce our usage of fossil fuels. Most of the sulphur can be removed before they're burnt but it cost more to do it and removing sulphur from fuels takes more energy.
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Increasing carbon dioxide increases climate change
The level of carbon dioxide in the atmosphere in increasing because of the large amounts of fossil fuels humans burn.
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Particles cause Global Dimming
Scientists think that it is caused by particles of soot & ash that are produced when fossil fuels are burnt. These particles reflect sunlight back into space, or they can help to produce more clouds that reflect the sunlight back into space
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Alternative fuels are being developed
Some alternative fuels have already been developed, and there are others coming. Many of them are renewable fuels so, unlike fossil fuels, they won't run out.However,none of them are perfect.
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Other cards in this set
Card 2
Front
number of protons equals number of electrons
Back
REMEBER
Card 3
Front
Atoms can have different numbers of protons, neutrons and electrons.It's the number of protons in the nucleus tat decides what type of atom it is
Back
Card 4
Front
Atoms of each element can be represented by a one or two letter symbol
Back
Card 5
Front
The periodic table is laid out so that elements with similar properties form columns
Back
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