Chemistry Core

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  • Created by: Amrita
  • Created on: 24-03-14 18:01
What is an element?
A substance that is made up of only one sort of atom
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Elements in the same group of the periodic table have the same number of electrons in their highest energy level. This gives them similar chemical properties
Atoms have no overall electrical charge
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What are elements in group 0 called?
The noble gases
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Why are noble gases unreactive?
Their atoms have stable arrangements of electrons
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When elements react, their atoms join with other atoms to form compounds
In molecules, the atoms are held together by covalent bonds.
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Compounds formed from metals and non-metals consist of ions
Compounds formed from non-metals consist of molecules.
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What is an ion?
An electrically charged particle
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What is the law of conservation of mass?
No atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants
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What is meant by thermal decomposition?
It means 'breaking down with heat'
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Explain the limestone cycle
Calcium carbonate is heated to form calcium calcium oxide and Co2. The calcium oxide reacts with water to produce calcium hydroxide. Then more water is added and filtered to make calcium hydroxide solution. Co2 is added to form calcium carbonate
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Carbon dioxide turns limewater cloudy
Carbonates react with acids to produce carbon dioxide, a salt and water
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Limestone is damaged by acid rain which reacts with it
Limestone is heated with clay to make cement
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Cement is mixed with sand to make mortar.
Cement is mixed with sand and aggregate to make concrete
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Ores contain enough metal to make it economical to extract
Ores are mined and may be concentrated before the metal is extracted and purified
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Metals apart from unreactive ones, are found as compounds that require chemical reactions to extract the metal
Metals that are less reactive than carbon can be extracted by reduction with carbon. e.g iron oxide is reduced in the blast furnace to make iron
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Metals more reactive than carbon are extracted by electrolysis
There are large amounts of energy in the extraction process making it expensive to produce
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What is smelting?
Extracting a metal from its ore by a process involving heating and melting
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Copper can be extracted from its ore by smelting
New ways of extraction are being researched to limit environmental impacts
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What is phytomining?
It uses plants to absorb metal compounds. The plants are then burned to produce ash containing the metal compounds
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What is bioleaching?
Bioleaching uses bacteria to produce leachate solutions that contain metal compounds
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Why is extraction expensive?
There are many stages in the process and large amounts of energy is needed
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Iron from the blast surface contains about 96% iron. Impurities makes the iron brittle so it has limited uses
Steels are alloys as they are mixtures of iron with carbon
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Low carbon steels are easily shaped whereas high carbon steels are hard
Stainless steels are resistant to corrosion
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Some metals are mixed with small amounts of similar metals to make them harder e.g copper,gold,iron
The elements in the central block of the periodic table are transition metals
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Transition metals are good conductors of heat and electricity and can be bent into shape
Low density and resistance to corrosion make aluminium and titanium useful metals
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What is crude oil?
A mixture of a large number of compounds
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Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms. Most of these are saturated hydrocarbons called alkanes
The bigger the molecule the higher the boiling point and viscosity. Flammability decreases as the molecule gets bigger
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Explain fractional distillation
Fractional distillation boils crude oil to purify it. Each substance in crude oil has different boiling points. The ones with the lower boiling points leave first.
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What gases are released into the atmosphere when a fuel burns?
Co2, water vapour, carbon monoxide, sulfur dioxide, nitrogen. Solid particles may be released which may contain soot and unburnt fuels
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Combustion of hydrocarbon fuels releases energy in which the fuels are oxidised
Sulfur dioxide and oxides of nitrogen cause acid rain. Co2 causes global warming. Solid particles cause global dimming
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Biofuels, including biodiesel and ethanol are produced from plant material
Hydrocarbons can be cracked to produce smaller, more useful molecules. This involves heating them to vaporise them. The vapours are then passed over a hot catalyst so that thermal decomposition occurs
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The products of cracking includes alkenes.
Alkenes react with bromine water, turning it from orange to colourless
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Alkenes can be used to make polymers such as poly(ethene) and poly(propene)
In these reactions, many small molecules join together to form large molecules
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Polymers can be developed into packaging and wound dressings
Polymers are not biodegradable which can lead to problems with waste disposal
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How are they solving the problem with non-biodegradable polymers
Plastic bags are being made from polymers and cornstarch so that they break down
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How is ethanol produced?
By hydration of ethene with steam in the presence of a catalyst or fermentation with yeast, sugar > carbon dioxide + ethanol
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Some fruits, nuts and seeds are rich in oils and can be extracted
The plant material is crushed and the oil is removed by pressing or distillation.
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Vegetable oils are important foods and fuels as they provide a lot of energy and nutrients
Vegetable oils have higher boiling points than water therefore they can be used to cook foods at higher temperatures rather than by boiling
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The higher temperature produces quicker cooking and different flavours. It also increases the energy that the food released when eaten. However it reduces the amount of nutrients
Oils do not dissolve in water but can be used to produce emulsions
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Emulsions are thicker than oil/water. They provide better texture and appearance, e.g ice creams.
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How can unsaturated oils be hardened?
By reaction them with hydrogen in a nickel catalyst at 60 degrees
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Unsaturated vegetable oils can be detected by reacting it with bromine water as it decolourises
Hydrogenated oils have higher melting points so they are solids at room temperature, making them useful as spreads
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The Earth consists of a core, mantle and crust, and is surrounded by the atmosphere
The Earth's crust and the upper part of the mantle are cracked into tectonic plates
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Convection currents are within the Earth's mantle and are driven by heat released by natural radioactive processes.
Convection currents cause the plates to move at relative speeds of a few cm per year
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The mantle is mostly solid but is able to move slowly
Earthquakes and volcanic eruptions occur at the boundaries between tectonic plates. It is the changes that occur at the plate boundaries which cause these
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For about 200 million years, the proportion of different gases in the atmosphere are the same as today. 80% nitrogen, 20% oxygen.
There are also small proportions of co2, water vapour and noble gases
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During the first billion years of the Earth's existence, there was intense volcanic activity
This activity released the gases that formed the atmosphere and water vapour that condensed to form the oceans
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One theory suggests that the Earth's atmosphere was mainly co2 and there was no oxygen, like Venus and Mars. But there was methane and ammonia
There is a theory that life formed due to the interaction between hydrocarbons, ammonia and lightning
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Plants and algea produce oxygen by photosynthesis which uses co2 from the atmosphere
Most of the carbon in the air gradually became locked up in rocks as carbonates and fossil fuels
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Co2 dissolves in oceans. Limestone was formed from shells and skeletons of marine organisms
Fossil fuels contain carbon and hydrocarbons that are remains of plants and animals
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Burning fossil fuels increases the level of co2 in the atmosphere causing global warming
The air is a mixture of gases with different boiling points and can be fractionally distilled to provide a source of raw materials used in industrial processes
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Other cards in this set

Card 2


Atoms have no overall electrical charge


Elements in the same group of the periodic table have the same number of electrons in their highest energy level. This gives them similar chemical properties

Card 3


The noble gases


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Card 4


Their atoms have stable arrangements of electrons


Preview of the back of card 4

Card 5


In molecules, the atoms are held together by covalent bonds.


Preview of the back of card 5
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