C3.

C3.

The periodic table
1. The early periodic table
  1. The periodic table of elements was developed as chemists tried to fit the elements into a pattern. It is arranged with similar elements grouped together
  2. Newlands table put the elements in order of atomic mass but failed to take account of elements that were unknown at the time
  3. Mendeleevs periodic table left gaps for the unknown elements and so provided the basis for the moon periodic table
2. The modern periodic table
  1. The proton number of an element determines its position in the periodic table
  2. The number of electrons in the outermost shell determines its chemical properties and what group it is in
  3. We can explain trends in reactivity through the group by distance of outermost elections from nucleus
3. Alkali metals
  1. The elements in group 1 are alkali metals because they form alkali solutions when they react with water
  2. Melting points decrease as you go down the group
  3. Reactivity increases as you go down the group
4. Transition elements
  1. Transition elements have higher melting points than group 1 elements and are stronger, harder and less reactive
  2. They can form ions of different charges and coloured compounds
  3. Good catalysts
5. Halogens
  1. Halogens are in group 7
  2. A more reactive halogen can displace a less reactive halogen from a solution of one of its salts
  3. Reactivity of halogens decreases as you go down the group
Water
1. Hard water
  1. Hard water contains dissolved calcium and magnesium salts
  2. Ions react with soap to form scum
  3. Temporary hard water can produce scale when heated
  4. Hard water is good for bones and teeth and may help prevent heart disease
2. Removing hardness
  1. Hard water can be softened by removing the ions that cause scale and scum
  2. Permanent hard water does not change when heated
  3. Both permanent and temporary hardness can be removed using washing soda or an ion exchange column
3. Water treatment
  1. Water for drinking should only contain low levels of dissolved substances
  2. Water is filtered and has chlorine added to it
  3. Pure water can be made by distilling it but it is very expensive
4. Water issues
  1. Fluoride helps to improve dental health
  2. Some think that people should have the right to choose if they get fluoride or not
Energy calculations
1. Comparing energy released by fuels
  1. When fuels and food react with oxygen energy I released in an exothermic reaction
  2. A calorimeter can be used to measure energy released by a fuel
2. Energy transfers in solution
  1. We can calculate the energy change for reactions in solution by measuring the temperature change
  2. Neutralisation and displacement reactions are both done using this technique
3. Energy level diagrams
  1. We can show the relative difference in the energy of reactants and products on energy level diagrams
  2. Catalysts lower the activation energy by providing an alternative path for the reaction
  3. Bond breaking is endothermic and bond making is exothermic
4. Calculations using bond energies
  1. In chemical reactions energy must be supplied to break bonds between atoms in the reactants
  2. In exothermic reactions the energy released making bonds is greater than needed to break the original bonds. It is the opposite in endothermic reactions
5. Fuel issues
  1. Much of the world relies on fossil fuels
  2. Fossil fuels are not renewable and cause pollution so we need to find an alternative
  3. Hydrogen is an alternative fuel and can be used to power vehicles
Analysis and synthesis
1. Tests for positive ions
  1. Most group 1 and 2 ions can be identified in their compounds through flame tests
  2. Lithium gives a crimson flame, sodium gives a yellow flame, potassium gives a lilac flame, calcium gives a red flame and barium a green flame
  3. When reacted with sodium hydroxide copper gives a blue precipitate, iron II gives a green precipitate and iron III gives a brown precipitate. Aluminium, calcium and magnesium ions give white precipitates
2. Tests for negative ions
  1. We can identify carbonates by adding dilute acid which produces carbon dioxide which make limewater go cloudy
  2. We can identify halides by adding nitric acid then silver nitrate solution. If the precipitate is white it is chloride, if it is cream it is bromide and if it is pale yellow it is iodide
  3. We can identify silicates by adding hydrochloric acid then bromium chloride solution. This forms a white precipitate
3. Titrations
4. Titration calculations
5. Chemical analysis
6. Chemical equilibrium
7. Altering conditions
8. Haber process
9. Economics of the haber process
Organic chemistry
1. Structures
2. Alcahols
3. Carboxylic acids and esters
4. Organic issues

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