MODULAR SCIENCE - Chemistry This gives a taste of chemistry topics that will be tested on the final two written papers Try and learn these facts – you will need to recall them and maybe apply them to something similar! Remember: chemistry is all about patterns!!
Paper 1 - chemistry What you should recall and apply from year 10 – all for F/H tier so if on higher paper they will be grade C type questions
Metals as elements Elements are made up of only one type of atoms They are arranged in order of their atomic mass and presented on the PT Elements with similar CHEMICAL properties are found in columns called GROUPS According to mass, Ar should be in group 1 and K in group 0 but then they don’t fit the chemical pattern – so they were swapped. Now we rank them according to the number of protons in their nucleus – and the pattern works
Metals • More than ¾ elements are metals • Found on the left-hand side of PT • Groups 1,2 and transition metal block between groups 2 and 3 • Properties of all metals: conduct heat and electricity, malleable (bent/hammered) group 1 vs transition metals Li Na K Cu Fe Zn Soft – cut easily Hard, strong, tough Low density – float on H2O high density
Group 1 – the alkali metals • GROUP 1 metals Li, Na, K all highly reactive - reactivity increases down group Metal + non-metal ionic compounds Eg. Sodium + oxygen sodium oxide lithium + chlorine lithium chloride All ionic compounds are solids, crystalline, white and dissolve in water to form colourless solutions.
Metals and water Metal + water metal hydroxide + hydrogen eg lithium + water lithium hydroxide + hydrogen potassium + water potassium hydroxide + hydrogen Hydroxides are alkalis (soluble bases) Test for hydrogen: light gas squeaky pop
Paper 1: Transition Metals • Useful as structural materials – iron as scaffolding, copper as electrical wiring • Compounds are coloured CuSO4=blue nickel chloride=greenCoCl2=pink Uses – pottery glazes/green weathering roof Catalysts: platinum = hydrogenation of oil to margarine iron: making ammonia ( Haber Process )
Paper 1: Reactivity Series • A league table of metals according to their reactivity • A more reactive metal will always displace a less reactive metal from its oxide or its solution • Eg copper oxide + zinc zinc oxide + copper • Eg copper sulphate + zinc zinc sulphate + copper
Extracting Metals Depends on their position in the reactivity series K Na Ca Mg Al C Zn Fe Pb Cu Ag Au Extract usingextract using native electricity carbon(CO) dig out More energy needed less energy needed very expensive cheaper But don’t forget rarity = expensive too!
Making Salts Acid + Alkaline Neutral + Water Hydroxide Sol Salt sol sulphuric acid + sodium hydroxide sodium sulphate + water The type of acid determines the salt name: sulphuric acid (metal name)sulphate hydrochloric acid (metal name)chloride nitric acid (metal name) nitrate
Year 11 work on structures and bonding • Changes of state melting evaporation/boiling Solid Liquid Gas freezing condensing • Atoms are made of 3 particles Think PENprotons, electrons and neutrons
ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”) The structure of the atom
MASS NUMBER = number of protons + number of neutrons 4 He SYMBOL 2 PROTON NUMBER = number of protons (obviously) The structure of the atom
Notice that the mass number is different. How many neutrons does each isotope have? 16 O 17 18 O O 8 8 8 Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more. Isotopes An isotope is an atom with a different number of neutrons: A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating.
39 K 19 Nucleus Electronic structure Consider an atom of Potassium: Potassium has 19 electrons. These are arranged in shells… The inner shell has _2_ electrons The next shell has _8_ electrons The next shell has _8_ electrons The next shell has the remaining __1 electron Electron structure = 2,8,8,1
This is where a metal bonds with a non-metal (usually). Instead of sharing the electrons one of the atoms “loses” one or more electrons to the other. For example, consider sodium and chlorine: Sodium has 1 electron on its outer shell and chlorine has 7, so if sodium gives its electron to chlorine they both have a FULL outer shell and are STABLE. Cl Na + - A positively charged sodium ion A negatively charged chloride ion Cl Na As opposed to covalent bonds, ionic bonds form strong forces of attraction between different ions due to their opposite CHARGES, causing GIANT IONIC STRUCTURES to form (e.g sodium chloride) with HIGH melting and boiling points: Ionic bonding
Notice that hydrogen has just __ electron in its outer shell. A full (inner) shell would have __ electrons, so two hydrogen atoms get together and “_____” their electrons: Now they both have a ____ outer shell and are more _____. The formula for this molecule is H2. When two or more atoms bond by sharing electrons we call it COVALENT BONDING. This type of bonding normally occurs between non-metal atoms. It causes the atoms in a molecule to be held together very strongly but there are weak forces between individual molecules. This is why covalently-bonded molecules have low melting and boiling points (i.e. they are usually gases or liquids). Covalent bonding Consider an atom of hydrogen:
Group 0 – The Noble gases Some facts… 1) All of the noble gases have a full outer shell, so they are very unreactive 2) They all have low melting and boiling points 3)They exist as single atoms rather then diatomic molecules • Helium is lighter then air and is used in balloons and airships (as well as for talking in a silly voice) • Argon is used in light bulbs (because it is so unreactive) and argon , krypton and neon are used in fancy lights
Potassium + water potassium hydroxide + hydrogen Group 1 – The alkali metals Some facts… 1) These metals all have 1 electron in their outer shell • Reactivity increases as you go DOWN the group. • They are soft and easy to cut – they float on water 4) They all react with water to form an alkali (hence their name) and HYDROGEN , e.g:
Decreasing reactivity Cl Cl Group 7 – The Halogens Some facts… 1) Reactivity DECREASES as you go down the group 2) They all have coloured vapours: chlorine bromine iodine Because they are non-metals they are brittle and crumbly when solid 3) They exist as diatomic molecules (so that they both have a full outer shell): 4) Because of this fluorine and chlorine are gases at room temperature and bromine is a liquid.
Methane, CH4 Carbon dioxide, CO2 Water, H2O Key Hydrogen Oxygen Carbon Sulphur Ethyne, C2H2 Sulphuric acid, H2SO4 Chemical formulae
Paper 2 - chemistry What you should recall and apply from year 10 – all for F/H tier so if on higher paper they will be grade C type questions
H H C C H H H H Ethane Increasing length H H H H C C C C H H H H H H Butane Hydrocarbons and crude oil Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: Longer chains mean… Less ability to flow Less flammable Less volatile Higher boiling point
Fractional distillation - separating the oil into useful parts (fractions) • A tall fractionating column is used – cool at the top and hot at the bottom • The oil is heated up into a gas (vapourised) • The smaller molecules go to the top and condense bottled gases • The heavier ones stay at the bottom and condense fuel oil and bitumen (road tar)
Cracking • Breaks down (cracks) the big not so useful hydrocarbon molecules into smaller more useful hydrocarbons • A catalyst and high temperatures are used this is called THERMAL DECOMPOSITION • New molecules called alkenes are also made Eg Paraffin petrol + ethene (fuel) (used to make plastic)
Burning Fuels (hydrocarbons) • The carbon parts burn to make carbon dioxide • The hydrogen parts burn to make water • Sulphur in the fuel burns to make sulphur dioxide – this then dissolves to make ACID RAIN Hydrocarbons + oxygen carbon dioxide + water Plastics like polyethene and polypropene are NOT BIODEGRADABLE – they WILL NOT ROT AWAY – this causes disposal problems
Earth Structure – the crust fold Turned upside down tilted fold fracture fold At the Earth’s surface sedimentary rocks exist mainly in LAYERS – the toplayers are usually the YOUNGEST HOWEVER the Earth has been subjected to very large forces causing folding, faulting and fracturing of rocks This demonstrates that the Earth’s crust is very unstablet You may also be asked to do some data handling on plate movements (tectonics) and the theory behind it
Yr 11 : Patterns of chemical change – paper 2 • Topics you should know about • Factors affecting the rate of a reaction • Enzymes – Fermentation • Exothermic & Endothermic reactions • The Haber Process • Fertilisers • Relative Formula Mass
Highly Flammable i Toxic Corrosive h Irritant Harmful Oxidising Agent RECOGNISE AND RECALL THESE HAZARD SYMBOLS
Rates of Reaction Chemical reactions occur when different atoms or molecules collide: • For the reaction to happen the particles must have a certain amount of energy – this is called the ACTIVATION ENERGY. • The rate at which the reaction happens depends on four things: • The temperature of the reactants, • Their concentration • Their surface area • Whether or not a catalyst is used
Sugar Alcohol + carbon dioxide Enzymes are denatured beyond 40OC Could be protease (found in the stomach) Could be amylase (found in the intestine) Enzyme activity 400C Temp pH pH Enzymes Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction. They can be denatured by high temperatures - so they don’t work Yeast is an example of an enzyme. It is used to help a process called fermentation: The alcohol from this process is used in making drinks and the carbon dioxide can be used to make bread rise. Enzymes work best in certain conditions:
Endothermic and exothermic reactions Step 1: Energy must be SUPPLIED to break bonds: Step 2: Energy is RELEASED when new bonds are made: EXOTHERMIC reactions feel HOT because HEAT EXITS ENDOTHERMIC reactions feel cold because HEAT ENTERS ( energy is lost from your hand!)
A + B C + D e.g. Ammonium chloride Ammonia + hydrogen chloride NH4Cl NH3 + HCl For example, consider copper sulphate: Hydrated copper sulphate (blue) + Heat Anhydrous copper sulphate (white) + Water CuSO4.5H2O CuSO4 + H2O Reversible Reactions Some chemical reactions are reversible. In other words, they can go in either direction: If a reaction is EXOTHERMIC in one direction what must it be in the opposite direction?
Nitrogen + hydrogen Ammonia Fritz Haber, 1868-1934 N2 + 3H2 2NH3 Nitrogen Mixture of NH3, H2 and N2. This is cooled causing NH3 to liquefy. Hydrogen Recycled H2 and N2 Making Ammonia Guten Tag. My name is Fritz Haber and I won the Nobel Prize for chemistry. I am going to tell you how to use a reversible reaction to produce ammonia, a very important chemical. This is called the Haber Process. To produce ammonia from nitrogen and hydrogen you have to use three conditions: • High pressure • 450O C • Iron catalyst
Relative atomic mass of O = 16 Relative atomic mass of H = 1 Relative formula mass, Mr The relative formula mass of a compound is blatantly the relative atomic masses of all the elements in the compound added together. E.g. water H2O: Therefore Mr for water = 16 + (2x1) = 18 Work out Mr for the following compounds: • HCl • NaOH • MgCl2 • H2SO4 • K2CO3 H=1, Cl=35 so Mr = 36 Na=23, O=16, H=1 so Mr = 40 Mg=24, Cl=35 so Mr = 24+(2x35) = 94 H=1, S=32, O=16 so Mr = (2x1)+32+(4x16) = 98 K=39, C=12, O=16 so Mr = (2x39)+12+(3x16) = 138