Wednesday 21 January 2015

Section 2- Metals

Extracting Metals:

  • are linked to the order of reactivity 
  1. Only metals less reactive than carbon can be extracted by a reduction reaction with carbon ----------> heating the ore with carbon monoxide 
    • more reactive elements form compounds more readily 
    • reduction= loss of oxygen 
  2. Hydrogen: metals above H react with acids to release H2 
Extracting Iron:
(Blast Furnace) 
Raw materials:
  1. Iron ore -----> iron
  2. Coke -----> almost pure carbon; reducing iron oxide to iron metal
  3. Limestone -----> take away impurities from slag 
  4. Air ------> allows the coke to burn 
Reducing Iron ore to Iron:

  1. Hot air blasted into the furnace -----> coke burns faster than normal. Raises to 1500C.  
  2. Coke burns and produces carbon dioxide:
    • Carbon and Oxygen ------> Carbon Dioxide 
    • C            +        O2    ------> CO2 
  3. Carbon monoxide 
    • Carbon dioxide and Carbon -----> Carbon monoxide 
    •          CO2          +         C     ----->          2CO 
  4. Carbon monoxide then reduces the iron ore to iron
    • Carbon monoxide + Iron(II) oxide ------> Carbon dioxide + Iron
    •          3CO             +       Fe2O3       ------>        3CO2        +  2Fe 
  5. Iron is molten at temperature also dense so goes to the bottom where it's tapped off 
Removing impurities: 
Slag forms as CaO from limestone reacts with rocks (SiO2) 
CaCO3 -----> CaO + CO2 
CaO + SiO2 ------> CaSiO3 (molten slag) 

  • Coolen to solid and used for:
    • road building 
    • fertiliser 

Uses of Iron:
  • steel 
  • buildings
  • car radio 
  • railings
REDOX -------> reduction and oxidation occur together 
Oxidising Agent --------> produces Oxygen (O2) in the process. reduced itself
Reducing Agent --------> gains Oxygen (O2) in the process. oxidising itself

Rusting of iron:
  • needs water and oxygen (from air) 
  • doesn't rust in boiled water or dried air 
How to prevent rusting?
Barrier methods: 
  • paint 
  • plastic coat 
  • tin plate 
  • grease 
  • coat in zinc 
Sacrificial methods: 
  • Attach above (more reactive) metal to the iron (e.g. zinc) 

Tuesday 20 January 2015

2f) Reactivity Series

 
Potassium K
Sodium Na
Calcium Ca
Magnesium Mg
Aluminium Al
Carbon Ca
Zinc Zn
Iron Fe
Tin Sn
Lead Pb
Hydrogen H
Copper Cu
Silver Ag
Gold Au

2e) Hydrogen and water

Prepared by:
Zn + H2SO4 -----> ZnSO4 + H2                        displaces 

Burns in air:
2H2 + O2 -----> 2H2O 

Physical test for water boils at 100C
Chemical test turns anhydrous copper sulfate -----> blue 


Sunday 18 January 2015

2d) Oxygen and Oxides

How to make O2:
2H2O2 (aq) -----> 2H2O (l) + O2 (g) 

metal oxides- bases
non metal oxides- acidic
water- neutral

Carbon dioxide prepared by
CaCO3 + HCl ------> CaCl + CO2 + H2

Delivery of CO2
Either upwards so that it's lighter than air
Or       downwards so that it is heavier than air

  • Under pressure- disowns 
  • used in fire extinguishers
Thermal disposition of copper(II) carbonate:
CuCO3(s) -----> CuO(s) + CO2(g) 

2c) Group 7 elements

Chlorine, bromine and iodine
called Halogens

Properties:


Group VII elements Atomic Number Colour At room temperature Boiling Point
Chlorine 17 green gas -34C
Bromine 35 red-brown liquid 59C
Iodine 53 dark grey solid 185C

Bonding in molecules:



Displacement reactions:

  • more reactive halogens displace less reactive ones 
  • a solution of its salt 
    • Cl2 + 2KBr -----> 2KCl + Br2 (orange-brown)
    • Cl2 + 2KCl -----> 2KCl + I2 (dark brown)
    • Br2 + 2KBr -----> 2KBr + I2 (dark brown) 
  • REDOX Reactions 
Summary: Chlorine is smaller than bromine has less outer shells of electrons sheilding the nucleus 
attracts electrons more readily 
More reactive as the atomic number decreases 

HCl gas vs HCl (aq) 
  • gas: covalently bonded 
  • no ions so can't conduct electricity 
  • not acidic 
HCl dissolved in water:
  • forms H+ (aq) and Cl- (aq) 
  • ions conduct electricity 
  • solution acidic 


Wednesday 14 January 2015

2b) Group 1 elements

The group 1 elements are lithium, sodium and potassium
  • They all react a similar way in water:

metal and water -------> metal hydroxide and hydrogen
2M(s)       2H2O(l)            2MOH(aq)                H2(g)


  • alkali metals 
  • reactive metals 
  • shiny silver when freshly cut
  • low density 
  • low melting point 

Metal Observations
Lithium (Li) Fizzes, floats and moves on the water surface
Sodium (Na) Fizzes, floats, forms a ball and moves around surface of water (may ignite)
Potassium (K) Fizzes, reacts vigorously and burns with a lilac flame (sometimes explodes)

Summary: Group 1 elements get more reactive as the atomic number increases 



1. Atoms increase in size 
2. Outer electrons further from nucleus 
3. Therefore they are easily lost 

Monday 12 January 2015

2a) The Periodic Table

Origins of the periodic table


  1. Newland's Octaves:
    • elements in groups have similar properties 
    • didn't leave gaps for undiscovered elements 
    • metals and non metals are mixed up
  2. Mendeleev 
    • arranged by mass
    • left gaps 
    • some elements in wrong order 
    • now arranged in order of atomic number 
LHS metals                                                                                                                  RHS Non-metals 

Groups- elements that have the same number of outer shells are part of the same group
              They have similar chemical properties and physical appearance is similar 

Periods- number of electrons or protons increases across period recurring patterns 

Transition Elements
  • metals 
  • hard/strong
  • high melting points 
  • unreactive
  • act as a catalyst 
  • form a coloured compound 
  • 3rd shelll being filled across period 

Section 2

Chemistry of the elements

1f) Ionic compounds + 1g) covalent compounds

Ionic bonding:

  • strong electrostatic attraction 
  • opposite charged ions 
  • throughout lattice 

Properties of ionic compounds:
  • high melting point 
  • strong electrostatic attraction 
  • giant ionic lattice 
  • soluble in water 
  • Ions attracted to polar water molecules 
  • conduct electricity 
  • ions can move and carry charge
A Lattice is a 3-D network of ions in fixed positions bonded together 


OIL RIG 

Oxidation- loses electrons                      Reduction- gains electrons 



Group 1 2 3 4 5 6 7 0/8
Charge 1+ 2+ 3+ X 3- 2- 1- X

Covalent bonding:
  • non metal with non metal 
  • outer shells overlap 
  • electron shared in pairs 
  • atoms achieve outer shells (full)
  • attracts both nuclei 


Properties of simple covalent molecules:
  • very strong bonds
  • low melting and boiling points 
  • insoluble in water 
  • no free electrons 
  • Don't conduct electricity 
  • soluble in organ solvents 
Intermolecular forces 
  • weak bonds
  • easily broken 
Giant covalent bonds 
  • strong bonds 
  • no free electrons 
  • rigid 
  • all atoms joined together 
  • covalent unreactive 
Diamonds 
  • rigid 
  • hard 
  • sparkly
  • four covalent bonds  
Graphite
  • layers three covalent bonds 
  • slide over each other 
  • free electrons 
  • good conductor of electricity 
  • lubricant 

Monday 5 January 2015

1c) Atomic structure


Nucleus- contains neutrons and protons
Protons- has a positive charge due to neutrons
Electrons- move around the nucleus in shells; negatively charged
2,8,8,2: Elements in the same group have the same number of outer shell electrons

Atoms consist of a nucleus in the centre, which has neutrons and protons. Protons have a positive charge due to neutrons. There are also electrons which move around the nucleus in shells and are negatively charged. Elements in the same group have the same amount of outer shell electrons.

Particle Relative Mass Relative Charge
Proton 1 +1
Neutron 1 0
Electron 1/2000 -1

  • Atomic Number tells you how many protons there are
  • Mass number is the total number of protons and neutrons in an atom
  • Isotopes have the same chemical reactivity but different number of neutrons they also have the same molecular formula but different structural formula.
  • The Relative atomic mass (Ar) is the average mass of all the isotopes of an element. It allows for the relative mass of each isotope and its relative abundance.
  • Relative Abundance is how much there is of each isotope compared to the total amount of the element in the world. This can be represented as a ratio, fraction or percentage.


The Periodic Table
Is an arrangement of elements in order of their atomic number

Electronic configurations of the 1st twenty elements

Element Electronic Configuration
Hydrogen 1
Helium 2
Lithium 2,1
Berylium 2,2
Boron 2,3
Carbon 2,4
Nitrogen 2,5
Oxygen 2,6
Fluorine 2,7
Neon 2,8
Sodium 2,8,1
Magnesium 2,8,2
Aluminium 2,8,3
Silicon 2,8,4
Phosphorus 2,8,5
Sulphur 2,8,6
Chlorine 2,8,7
Argon 2,8,8
Potassium 2,8,8,1
Calcium 2,8,8,2