Chemistry Further

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The early periodic table
Elements were classified based on their properties and atomic weights.
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Newlands table
In 1863 Newlands proposed his law of octaves. Similar properties every 8th elements. After calcium the properties did not match so his table was not accepted by scientists.
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Mendeleevs table
In 1869 Mendeleev produced a table which had gaps left for undiscovered elements. He predicted the properties of these elements and they were confirmed once the elements were discovered. His table became the basis for the modern periodic table.
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The modern periodic table
Protons and electrons were discovered early 20th century. The elements were arranged in the periodic table in order of their atomic numbers(proton numbers) and were lined up in vertical groups.
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Reactivity of metals
When metals react they lose electrons, so the reactivity of metals in a group increases going down the group.
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Reactivity of non-metals
When non-metals react they gain electrons so the reactivity of non-metals decreases going down a group.
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Group 1
Group 1 is the alkali metals. They are all metals that react readily with air and water.
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Group 1 - properties
They are soft solids at room temperature with low melting and boiling poins that decrease going down the group. They have low densities, so lithium, sodium and potassium float on water.
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Group 1 reacting with Group 7
They react with the halogens to form salts that are wite or colourless crystals
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Reactivity trend in Group 1
Reactivity increases going down Group 1 because the outer electron is less strongly attracted to the nucleus as the number of occupied energy levels increases and the atoms get larger.
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The tranisitonal metals
The transitional metals(elements) are found in the periodic table between Groups 2 + 3
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The tranisitonal metals - properties
Except for mercury they have higher melting and boiling points than the alkali metals. they are malleable and ductile and they are good conductors of heat and electricity.They react slowly or not at all with oxygen and water. Most are strong.
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The tranisitonal metals - compounds
They form positive ions with various charges. Compounds on transition metals are often brightly coloured.
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Group 7
The halogens are non-metallic elements, they exist as smal molecules made up of pairs of atoms.
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Group 7 - properties
They have low melting and boiling poitns that increase going down the group. At room temperature flourine is a pale yellow gas, chlorine is a green gas, bromine is a red-brown liquid, iodine is a grey solid. Iodine easily vaporises to a violet gas
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Group 7 - compounds
The halogens form ionic compounds with metals in which the halide ions have a charge of 1-.
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Reactivity trend in Group 7
The reactivity of the halogens decrease going down Group 7 because the attraction of the outer electrons to the nucleus decreases as the number of occupied energy levels increases.
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Scum
Scum is formed when soap reacts with dissolved compounds in hard water.
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Scale
Scale is formed when temporary hard water is heated it covers pipes and heating elements.
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Difference between soft water and hard water
Hard water contains dissolved compounds that react with soap to form an insoluble solid
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Hard water can be made soft by..
..removing the dissolved calcium and magnesium ions that react with soap
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Temporary hard water is softened by heating
Temporary hard water contains hydrogencarbonate ions HCO3-. The HCO ions decompose when heated to produce carbonate ions, water and carbon dioxide
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Temporary hard water being softened - equation
2HCO^3-(aq) -> CO3^2-(aq) + H2O(l) + CO2(g)
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Ion-exchange column
They are packed with a resin containing sodium or hydrogen ions. When hard water is passed through, calcium and magnesium ions become attached to the resin and the sodium/hydrogen takes their place in the water as they don't react with soap.
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Water filters
They can be used to improve the taste of water, the often contain carbon and an ion-exchange resin to remove soluble substances. They contain silver to prevent growth of bacteria.
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Pure water
Pure water can be made by distillation, this require too much energy for it to be done on a large scale as it would be too expensive.
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3 main stages of producing water that is fit to drink
Suitable source, removal of solids, killing of microbes
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Hard water issues
Hard water causes problems in heating systems and with washing, but if used for drinking it has health benifits
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Chlorine
Chlorine is effective in killing microbes in water, however chlorine is poisonous and it can produce other toxic commpounds and must be carefully controlled to minimise the risk
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Flourine
Flourine is added to toothpastes and to water supplies to help prevent tooth decay. One argyment against adding flourine to water is that people should be able to choose to take extra flouride or not
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Comparing the energy released - equation
Q=mc(^)t Q is the amount of energy transferred to the water in joules. m is the mass of water in grams. c is the specific heat capacity of water. (^)t is the temperature change
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Exothermic
When energy is released during a reaction
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Endothermic
When energy is taken in during a reaction
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Calorimeter
A Calorimeter is used to measure the amount of energy released when a substance burns. The simplest calorimeter is some water in a glass beaker or metal can.
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Solid added to water
When a solid is added to water or an aqueous solution we assume that the volume of the solution does not change
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Energy change
The difference between the energy levels of reactants and products is the energy change for the reaction
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Activation energy
The minimun energy needed for the reaction to happen is called the activation energy
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Catalyst
When using a catalyst the activation energy is lower.
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Hydrogen as a fuel - advantages
Hydrogen has its advantages, it burns easily and releases a large amount of energy per gram. It produces no carbon dioxide when it is burned, only water.It can be burned in combustion engines or in fuel cells. It can be produced from renewable source
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Hydrogen as a fuel - disadvantages
Supply, storages and stafety problems. Vehicles that use fuel cells need to match the performance, convenience and cost of petrol and disesel vehicles
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Lithium (Li+) flame colour
Crimson (red)
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Sodium (Na+) flame colour
Yellow
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Potassium (K+) flame colour
Lilac
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Calcium (Ca2+) flame colour
Red
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Barium (Ba2+) flame colour
Green
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White percipitates
Are formed from ions of aluminium, calcium and magnesium ions. When excess sodium hydroxide solution is added the precipitate of sluminium hydroxide dissolves.
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Copper(II) hydroxide percipitate
Blue
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Iron(II) hydroxide percipitate
Green
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Iron(III) hydroxide percipitate
Brown
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Test for Carbonate ions
Add dilute hydrochloric acid to the substance to see if it fizzes. If it does and the gas produced turns limewater milkly, this substance contains carboante ions.
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Carbonate ions equation example
2HCl(aq) + CaCO3(s) -> CaCl2(aq) + H2O(l) + CO2(g)
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Test for Halide ions
Add dilute nitric acid and then silver nitrate solution. Chloride ions give a white precipitate. Bromide ions give a cream precipitate. Iodide ions give a yellow precipitate
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Halide ions equation example
AgNO3(aq) + NaCl(aq) -> AgCl(s) + NaNO3(aq)
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Test for Sulfate ions
Add dilute hydrochloric acid and then barium chloride solution. If a white precipitate forms, sulfate ions are present
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Sulfate ions equation example
BaCl2(aq) + MgSO4(aq) -> BaSO4(s) + MgCl2(aq)
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Titration
Pipette is used to measure the volume of alkali that is put into a flask. An indicator is added to the alkali. A burette is filled with acid, which is then added gradually to the flask. When the indicator changes colour the end point is reached
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Hydroxide precipitates
Cooper and iron form coloured compounds, like many other transition metals. Coloured hydroxide precipitates form when a few drops of sodium hydroxide solution are added to solutions of the metal ions
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If the forward reaction produces more molecules of gas..
.. an increase in pressure decreases the amount of products formed. .. a decrease in pressure increases the amount of products formed.
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If the forward reaction produces fewer molecules of gas..
..an increase in pressure increases the amount of products formed. ..a decrease in pressure decreases the amount of products formed.
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If the forward reaction is exothermic..
..an increase in temperature increases the amount of products formed. ..a decrease in temperature increases the amount of products formed.
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If the forward reaction is endothermic..
..an increase in temperature increases the amount of products formed. ..a decrease in temperature decreases the amount of products formed.
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The Haber Process
Makes ammonia, which can be used to make fertilisers and other chemicals. Nitrogen from the air and hydrogen are purified and mixed in correct proportions.
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The Haber Process - catalyst
The gases are passed over an iron catalyst at a temperature of about +450 and a pressure of about 200 atmospheres. These conditions give a fast rate of reaction and a reasonable yield of ammonia.
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The Haber Process - reaction
N2(g) + 3H2(g) <-> 2NH3(g)
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The Haber Process - products
The gases that come out of the reactor are cooled so the ammonia condenses. The liquid ammonia is separated from the unreacted gases. The unreacted gases are recycled so they are not wasted.
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Alcohol functional group
-OH
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Carboxylic acids functional group
-COOH
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Esters functional group
-COO-
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Ester example
Ethyl ethanoate
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Properties of alcohol
Alcohol mixes well with water and produces neutral solutions. Alochols burn in air, when burnt completely they produce carbon dioxide and water. Sodium reacts with alcohols to produce hydrogen gas, this reaction is less vigorous than with water.
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Oxidising alcohols
Alcohols can be oxidised by chemical oxidsing agents such as potassium dichromate to produce carboxylic acids.
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Alcohol uses
Ethanol is used in wine, beer and other alcoholic drinks. Many organic substances dissolve in slcohols and so this makes them useful solvents.
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Carboxylic acids dissolve in water to produce
They produce solutions with a pH value of less than 7. They have the properties of a typical acid.
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How are carboxylic acids different from other acids
They react with alcohols in the presence of an acid catalyst to produce esters. Ethanol reacts with ethanonic acid when mixed with sulfuric acid as a catalyst, to produce ethyl ethanoate and water.
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Strong acids
Acids that ionise completely in aqueous solutions aer known as strong acids.
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Weak acids
Acids that do not ionise completely in aqueous solutions are known as weak acids
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Other cards in this set

Card 2

Front

In 1863 Newlands proposed his law of octaves. Similar properties every 8th elements. After calcium the properties did not match so his table was not accepted by scientists.

Back

Newlands table

Card 3

Front

In 1869 Mendeleev produced a table which had gaps left for undiscovered elements. He predicted the properties of these elements and they were confirmed once the elements were discovered. His table became the basis for the modern periodic table.

Back

Preview of the back of card 3

Card 4

Front

Protons and electrons were discovered early 20th century. The elements were arranged in the periodic table in order of their atomic numbers(proton numbers) and were lined up in vertical groups.

Back

Preview of the back of card 4

Card 5

Front

When metals react they lose electrons, so the reactivity of metals in a group increases going down the group.

Back

Preview of the back of card 5
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