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73 Cards in this Set
- Front
- Back
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How originally were elements arranged? |
There was no understanding of protons, electrons or atomic structure So elements were categorised on their physical properties, chemical properties and relative atomic masses |
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What was Newland's octaves? |
He noticed that every 8th element had similar properties However the third row didn't work out as he didn't leave any gaps for new elements |
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Why was Newland's work criticised? |
Not all the groups had similar properties - there were anomalies He mixed up metals and non-metals He didn't leave gaps for future elements to be discovered |
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What did Dmitri Mendeleev do? |
He put the elements in order of atomic mass However he left gaps for future elements in order to keep the properties in groups Therefore he could predict the properties of the undiscovered elements and where they would fit |
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What did scientists think of the periodic table? |
At first they weren't very impressed by it However soon newly discovered elements fitted into the gaps After more evidence scientists realised it could be a useful tool to predict elements properties |
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How is the modern periodic table formulated? |
When elements, protons and neutrons where discovered elements were ordered in atomic no. Electrons in an atom are set in shells Group - number of electrons in outer shell Periods- number of electron shells |
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Why do group 7 metals decrease in reactivity and group 1 metals increase in reactivity as you go down the group? |
The + nucleus attracts the - electrons The more shells the further from the nucleus the outer electron is so the less attraction The more shells the more shielding so the less attraction from the nucleus to the electron This means that in group one it gets more reactive down the group (easily lose an electron) In group 7 - less easily gain an electron |
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What are the alkali metals? |
These are the group 1 metals They all have one outer shell electron so they are very reactive as they want to lose this electron They form ionic compounds with non-metals so gain a full outer shell (by losing 1 electron) Produce white compounds that dissolve in water to form colourless solutions |
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How do alkali metals react with water? |
They react vigorously and produce hydrogen They form hydroxides which dissolve in water to give alkaline solutions This therefore, would change the indicator colour to purple |
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What are the trends going down the halogens? |
* Halogens are group 7 electrons They become less reactive They have a higher melting and higher boiling point |
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What coloured vapours are the halogens? |
Fluorine - yellow gas Chlorine - green gas Bromine - red-brown gas Iodine - Purple gas |
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What is a halide ion? |
Halogens form ionic bonds with metals They form -1 charged ions These ions are called halides They exist as diatonic molecules (in pairs) |
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How do halogens displace? |
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt eg. Cl2 (g) + 2KI (aq) ---> I2 (aq) + 2KCl (aq) |
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What are the transition metals? |
They ate typical metals found between group 2 and group 3 in the centre of the periodic table They are good conductors of heat + electricity They are very dense, strong and shiny They are less reactive than group 1 metals They have higher melting points than G1 metals They often have more than 1 type of ion which can form different coloured compounds |
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Why are transition metal compounds coloured? |
The transition metal ion they contain results in different colours EG. Copper sulphate is blue These can be used in gemstones, pottery glazes |
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What are other uses of transition metals? |
They are good as catalysts Iron - used in the haber process Manganese oxide- decomposition of hydrogen peroxide Nickel - Hydrogenation |
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What is hard water? |
Water with high concentrations of calcium and magnesium ions They are harder to lather with soap However the calcium ions are good for healthy teeth and bones and hard water could reduce the risk of developing heart disease |
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What are the problems with hard water? |
When heated they form scale as the calcium hydrocarbon ate in temporary hard water thermally decomposes to form calcium carbonate This blocks pipes and reduces heating efficiency With soap scum is also formed - less lather used |
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What are the two types of hard water? |
Temporary = caused by hydrogen carbonate ions Permanent caused by dissolved calcium sulphate |
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How is temporary hardness removed? |
This can be removed by eating as scale is formed and this can then be removed separately |
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How can both types of hard water be removed? |
Washing soda can be added (sodium carbonate) as this forms an insoluble precipitate removing the calcium and magnesium ions Ion exchange column can be used which replace the calcium and magnesium ions with sodium ions ( sodium ions often need to be replaced) |
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What are the stages of water treatment? |
Water is collected from rivers and rainfall and collected in reservoirs The water passes through grills to remove big objects and sticks Chemical coagulants are added to clump the particles together They are then removed through gravel filters Water is chlorinated to kill of harmful microbes |
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What further treatments do people do to their water? |
People buy filters using carbon or silver The carbon is supposed to remove the chlorine taste and the silver is used as an antibacterial Some people also use ion resin columns (hard) |
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What are the positives of water companies adding chlorine and fluoride? |
F- Can help to reduce tooth decay C - Prevents disease by killing microbes |
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What are the negatives of water companies adding chlorine and fluorine? |
C - Increase in certain cancers? - Toxic by-products could cause cancer? F- Could cause cancer and bone problems? People believe that the consumer should have a choice of whether to have it added |
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What is a reversible reaction? |
A reaction in which the products of the reaction can react themselves to produce the original reactants and this occurs constantly A +B ---> <-- C + D |
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What is equilibrium? |
In a closed system equilibrium will always be reached This is when the amount of reactants and products will reach a balance and remain there The reactions still occur just at the same rate so nothing changes |
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How does temperature affect equilibrium? |
If you raise the temperature the endothermic reaction will increase to use up the heat If you lower the temperature the exothermic reaction will increase to give out more heat |
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How does pressure affect equilibrium? |
If you raise the pressure the reaction is favoured with the less gas molecules (less volume) If you lower the pressure the reaction is favoured with the more gas molecules |
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How does adding a catalyst affect the equilibrium position? |
It doesn't as both the forward and backward reaction will be increased by the same amount The only change is that the reaction will reach equilibrium faster than without a catalyst |
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Where do nitrogen and hydrogen come from to make ammonia? |
Nitrogen comes from the air (78%) Hydrogen comes from either natural gas or other sources such as crude oil |
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What are the conditions for the Haber process? |
It is a reversible reaction 200 Atmospheres ( favours forward reaction) 450 degrees This is a compromise as although it favours the backwards reaction it gives a better rate of reaction than a lower temperature would Nickel catalyst |
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What are the end steps of the Haber process? |
Tha Ammonia is cooled and liquified and removed as a liquid The unused nitrogen and hydrogen are recycled back to be used again |
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What is the general formula of an alcohol? |
Their functional group is OH The general formula is CnH2n+1OH To show an alcohol you must separate it with the OH at the end to show it properly |
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What are the properties of alcohols? |
For the first three alcohols... They are flammable and burn in air to produce carbon dioxide and water They dissolve in water to form neutral solutions They act with sodium to give hydrogen and an alkoxide |
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How are alcohols used as solvents? |
They can dissolve most compounds that water dissolves, and more such as (hydrocarbons, oils and fats) They can be used for perfumes, aftershaves, cleaning brushes. |
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How are alcohols used as fuels? |
They can be used as spirit burners as they burn cleanly and don't smell They are also a renewable resource Sugar cane can be used to form ethanol therefore it would be carbon neutral |
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What is the functional group of a carboxylic acid? |
Their functional group is COOH Their names end in " anoic acid "
O // - C \ OH |
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How do carboxylic acids react? |
They react with carbonates to form CO2 The salts formed by this end in "anoate" They dissolve in water to form acidic solutions as when they dissolve they ionise to release H+ ions |
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What are the differences between strong and weak acids? |
Strong acids - All the H+ ions fully ionise in solution so they have a low pH Weak acids - Not all their H+ ions fully ionise fully in solution so they have a high pH |
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What are some of the uses of carboxylic acids? |
Ethanoic acid can be made from oxidising ethanol ( leaving wine out ) Ethanoic acid can be dissolved in water to make vinegar Citric acid can be used in fizzy drinks and to remove scale Longer chain- used for soaps and detergents Can be used in the production of esters |
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What is the functional group of an ester? |
They have the functional group COO They are formed from an alcohol and a carboxylic acid An acid catalyst is used (e.g. conc. sulphuric acid) |
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How are the names of esters formed? |
The first bit is from the alcohol and ends in yl e.g. ethanol -----> ethyl The second bit is from the acid and ends in annoate eg Propanoic acid ----> propanoate |
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What are the properties of esters? |
They have pleasant smells They are volatile They are flammable so can be very dangerous They don't mix well with water They don't mix well with alcohols or other solvents |
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What are the uses of esters? |
They are used in perfumes Used for flavourings and aromas They can be used in ointments They can be used as solvents for paint or ink |
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What are the problems with esters? |
Whaling their fumes can irritate mucous membranes in the nose and mouth They are heavier than air and very flammable They can be toxic in high doses Dangerous as synthetic food additives |
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What is a mole? |
The amount of substance in the restive atomic or formula mass of a substance in grams |
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What is concentration? |
The amount of moles or grams per dm cubed The more solute dissolved in a given volume the higher the concentrated Moles = ------------ Volume |
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How is a titration used? |
This can be used to work out concentration by finding out how much acid is needed to neutralise an alkali Phenolphalein indicator can be used as it has a sharp colour change Pink : alkali Colourless : acids |
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How can energy transfer of a chemical reaction be measured? |
By taking the temperature and placing the reaction in a polystyrene cup and measuring the temperature change A draft excluder and lid can reduce energy being lost |
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What is an exothermic reaction? |
= One which gives out energy to the surroundings The temperature of the surroundings increases E.G. fuel burning and neutralisation reaction |
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What is an endothermic reaction? |
One in which energy is taken in from the surroundings The temperature of the surroundings decreases E.G. Photosynthesis |
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What happens in all chemical reactions? |
Old bonds are broken and new bonds are made Energy must be supplied to break bonds Energy is always released when bonds are formed Breaking bonds - endothermic Making bonds - endothermic |
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Describe the energy changes in an endothermic reaction? |
The energy required to break bonds is greater than the energy released when new bonds are formed The overall energy change therefore is + The products are higher than the reactants (in a graph) |
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Describe the energy changes in an exothermic reaction? |
The energy released in bond making is greater than the energy used in bond breaking The overall energy change therefore is - On a graph the reactants are higher than the products |
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How can fuel energy be measured? |
A calorimeter can be used by using a metal container and measuring time to heat water to a certain temperature This can be calculated by looking at the mass of fuel burnt and temperature change |
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What is the equation for energy transferred? |
Q = water mass X SHC of water X temp change J = grams X J X degrees |
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What are the consequences of burning fuels? |
They can release CO2 - a green house gas This therefore can cause global warming Developing alternative sources costs money Common fuels are running out therefore the prices of these fuels increase |
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What is activation energy? |
The minimum amount of energy needed by reactant particles to break their bonds |
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What does a catalyst do to a reaction ( bond energies)? |
It provides an alternative pathway for the reaction with a lower activation energy Therefore on a bond energy diagram with a catalyst the reaction will have a lower curve however the overall energy change for the reaction will stay the same (start and end in same places) |
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How can the overall energy change for a reaction be calculated? |
You can read it of an energy level diagram Or you can subtract the bond making from the bond breaking and then indicate through the positive or negative sign whether it is exo or endo thermic |
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How can hydrogen be used as a fuel? |
If hydrogen gas is reacted with oxygen it produces water as an exothermic reaction This can be used in combustion engines It is a very clean fuel However you need a special engine, it is hard to store and you still need energy to make it ( which comes from burning fossil fuels) |
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How does a fuel cell use oxygen? |
It is an electrical cell which is supplied with fuel and oxygen and uses energy from the reaction to generate electricity Hydrogen can be used as this fuel Unlike a battery cell they don't need recharging |
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What are the positives of hydrogen fuel for cars? |
There are no pollutants produced Help countries become less dependent on crude oil which is non-renewable |
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What are the negatives of hydrogen fuel in cars? |
It is a gas so takes up lots of space to store It is explosive so is hard to store safely It is often made from hydrocarbons ( from fossil fuels) or by electrolysis of water which uses electricity which is generated from fossil fuels |
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What is the flame test? |
It is when a sterilised piece of nichrome wire is put into a bunsen burner flame with a sample of a compound on it and it creates a coloured flame to indicate which metal ions are present |
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What metal ions are indicated by the flame test? |
Lithium - Crimson Sodium- yellow Potassium - lilac Calcium - red Barium - green |
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How can sodium hydroxide be used to identify other metal ions? |
If you add sodium hydroxide solution to some compounds a coloured insoluble hydroxide is formed indicating a particular metal present |
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What metal ions are indicated by adding sodium hydroxide? |
Calcium - White precipitate Copper - Blue precipitate Iron 2 - Green precipitate Iron 3 - Brown precipitate Aluminium - White precipitate Magnesium - White precipitate |
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How can you tell the different between calcium, aluminium and magnesium ions? |
Aluminium's white precipitate dissolves in excess sodium hydroxide The other two don't dissolved in excess Then calcium can be put in the flame test and will go red whereas magnesium won't |
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How can you test for carbonates? |
You can react the sample with acid You can then test if the gas is carbon dioxide by bubbling it through limewater and if it is carbon dioxide the limewater will go cloudy If carbon dioxide is produced it is a carbonate As : CASHOCO |
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How can you test for halide ions? |
Add dilute nitric acid Then add silver nitrate solution Chlorine - white precipitate Bromide - cream precipitate Iodide - yellow precipitate |
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How can you test for sulphate ions? |
Add dilute hydrochloric acid Then add barium chloride solution A white precipitate being formed indicates sulphate was present |
