CHEMISTRY UNIT 1

CHEMISTRY UNIT 1

1. C1.1

   • Always same number of protos and electrons in an atom.
     • Metal + Oxygen - metal oxide
     • Metal + Water - metal hydroxide + hydrogen
     • In compounds the charges cancel out like LiF
       • Non metal atoms share electrons, they dont form ions but they form molecules like H2S
   • Shells , 2 ,8, 8 .18
   • Atomic number is the nuber of protons
   • Mass number is the number of protons add the number of electrons
   • Number of neutrons is the mass number minus the number of protons
   • Atoms with same no. of electrons belong in same group in periodic table
   • Noble gases are unrreactive
   • Group 1 is very reactive
   • Group Number is the amount of electrons in the outermost shell
     • The no. of electrons in the outer shell determines the way it reacts
   • When a metal bonds with a non metal, the metal atom gives one or more electrons to the non metal
     • This is Ionic bonding and both atoms become charged particles called ions
     • Metal atoms form +
     • Non metal atoms form --

2. C1.2

   • Limestone is made up of mainly calcium carbonate - CACO3 which is quarried
   • Thermal Decomposition is breaking down with heat
   • Calcium Carbonate when heated breaks down to form Calcum Oxide and Carbon Dioxide
   • Powdered limestone and powdered clay is heated to make cement
   • Cement, sand, crushed rock and water makes concrete
   • To make lots of calcium oxide, we fill a kiln with crushed limestone and heat stonrgly with hot air
     • Calcium oxide comes out bottom and waste gases like CO2 come out top
   • Caronates react with dilute acid to form a salt water and CO2
     • When water is added to calcium carbonate, calcium hydroxide is made
       • Calcium Hydroxide is Ca(OH)2
         • If you add more water and filter you get Calcium Hydroxide solution or limewater.
           • Add Carbon Dioxide and you get Calcium Carbonate again.
           • Mortar holds building materials together, eygptians used limestone and water which hardened wth age
         • Mortar is made by mixing crushed rocks or small stones cement sand and water

3. C1.3

   • A metal ore conatins eough metal to make it economic to extract
   • We can find gold and other unreactive metalsi their native state.
     • The reactivity series helps us decide the best way to extract a metal.
   • Metals below carbon on the reactivity series can be extracted by carbon reduction
   • Metals more reactive than carbon are extracted using electrolysis
   • Iron ore contains iron combined with oxygen, we can use carbon reduction to extract the iron
     • we use a blast furnace but the iron has limited uses as it contains 96% iron with carbon impurities making it brittle and not easily compressed
       • Removing all impurities gives us pure iron which is very soft and easily shaped
         • If we want useful iron we must mix other elements and this is called an alloy, steel is an alloy
           • Carbon steels are the cheapest, cars knives and containers
             • Low alloy seels are more expensive and even more expensive are high alloy steels
             • Stainless steels are resistant to corrosion
               • Aluminium resists corrosion, and is very light, we use it for drink cans, bikes,cooking foil
                 • Using electrolysis to extract aluminium is a very expensive process we need alot of electricity
                   • Titanium is very strong and resistant to corrosion and has a very high melting point. Used for, hip joints,jet engines, aircrafts
                   • Titanium cannot be extracted with copper as they react making it brittle so we need a more reactive metal like sodium but this needs to be extracted using electroysis as well $$
                   • Transition metals are, good conducters, malleable, strong and high melting point and form coloured compounds
             • Most copper is extracted by smelting copper rich ores although our limited supplies of copper ores are becoming scarce
           • Bacteria is used in bio leaching and plants in phytomining
         • Copper can be extracted from copper solutions using electrolysis, it is also used to to purify impure copper

4. C1.4

   • Crude oil is a mixture of many different compounds, before using crde oil we must separate it into different substances with similar boiling points
   • Many of the compounds in crude oil are hydrocarbons, alkanes are saturated hydrocarbons, they contain as many hydrogen atoms as possible
   • We seperate crude oil into fractions using fractional distillation, the properties of each fraction depend on the size of their hydrocarbon molecule
   • Lighter fractions make btter fuels as they ignite easier and burn well with cleaner smoke
     • When we burn hydrocarbons in plenty of air the carbon and hydrogen are completely oxidised they produce CO2 and H2O
       • In insufficient oxygen we get poisonous carbon monoxide we can get particulates and unburnt hydrocarbons
         • Hydrogen is a potential fuel for the future
     • Sulfur impurities in fuels burn to form sulfur dioxide which causes acid rain
       • Changing the conditions in which we buen the fuels can change the products
       • At high temps nitrogen reacts with oxygen to form nitrogen oxide which can cause breathing problem
         • Advantages of biofuels, its carbon neutral, better for thr environment, cheaper
       • Biofuels are a renewable source of energy that could be used to replace some fossil fuels, biodiesal can be made from vegetable oil
         • Disadvantages are, uses large areas of farmland, destruction of habitats, temperature must be just right
   • Crude oil is fed in at the bottom of the fractioning coloumn as hot vapour, the coloumn is hot at the bottom and gets cooler as you go up, the gases condense when they reach thier boiling point and the liquids are collected at different levels

5. C1.5

   • We can split hydrocarbon molecules up into smaller molecules by cracking, - mixing them with steam and heating to a high temp or by passing the vapours over a hot catalyst
     • Cracking produces saturated hydrocarbons which are used as fuels and unsaturated hydrocarbons called alkenes.
       • Ethanol can be made from ethene reacting with steam in the presence of a catalyst, this is called hydration
       • Using ethene is to make ethanol needs non renewable crude oil as its raw material whereas as fermentation uses renewable plant material.
       • Hydration is faster and produces no waste products but its non renewable
     • Alkenes react with orange bromine water making it turn colourless
     • plastics are made of polymers, polymers are large molecules made when monomers join together
     • Ethanol is made by fermenting sugar using the enzymes in yeast, CO2 is also made in this reaction

6. C1.6

   • Vegetable oils can be extracted from plants using distillation or by pressing
     • Vegetable oils have a high energy content and provide nutrients andn be used to make biofuels
       • An emulsifier is a molecule with a tail. The head is attracyed to water and is called the hydrophilc part. The tail is attracted to oil and is called the hydrophobic part. So the molecle dissolves in the oil and the other part in water
     • Unsaturated oils contain carbon carbon C=C double bonds we can detect them as they decolourise bromine water
   • Vegetable oils are hardened by reacting them with hydrogen to increase their melting points. This makes them solids at room temperature which are suitable for spreading.
   • The hardening reaction takes place at 60 degrees with a nickel catalyst. The hydrogen adds onto C=C bonds in the vegetable oils molecules
   • Oils and water can be dispersed in each in other to produce emulsions which have special properties. Emulsions made from vegetable oils are used in many foods,such as salad dressings, ice creams cosmetics and paints

7. C1.7

   • The earths crust and upper mantle is cracked into a number of big piecs called the tectonic plates which are constantly moving
   • The motion of the tectonic plates is caused by convenction currents in the mantle due to radioactivite decay
   • Earthquakes and volcanoes happen where tectonic plates meet
     • The earths early atmosphere was formed by volcanic activity, it probs consisted mainly of carbon dioxide there may have been water vapour and amonia and methane
   • As plants spread over the earth the level of O2 i the atmosphere increased
     • Gases in the air 78% Nitrogen 21 % Oxygenand CO2 and argon