JOHN NEWLANDS placed the elements known in his time, and organised them in a specific way9 in atomic weight). However, it was MENDELEEV who cracked the periodic table.
MENDELEEV created a periodic table, and left gaps where elements had yet to be discovered. He saw simularities in the elements and created a specific organisation, recognising the simularities of the elements.
COLOUMNS of elements are called groups. ROWS of elements are called periods. The group number tells you how many electrons are on the outer shells and the period number tells you how many shells in the atom.
The attraction of a halogen for a extra electron gets greater going up groups in the periodic table.
Uses of BROMINE and IODINE:
- Leaded petrol
- Animal feed suppliments
The outer electrons of a atom get further away meaning they are more sheilded from the nucleus. We use a more reactive halogen to displace a less reactive halogen from solution.
EXAMPLE: CHLORINE will displace BROMINE because chlorine is more reactive.
TRANISTION ELEMENTS are the elements found in between group 2 and group 3 of the periodic table. PROPERTIES INCLUDE:
- Not massively reactive
- They are all highly dense
- Melting points show no regular pattern, other than being high
- React slowly with oxygen, water and acid
- Mostly form colour compounds
- Their 3rd outer shell can hold 18 electrons
- Good conductors
Many transition metals are catalysts; Nickel is used in oil hydogenation and Titanium is used in plastic manufacturing.
HARD WATER FORMS SCUM - Reacts with calcuim and magnesium ions to form scum.
- Rain water doesnt form any dissolved salts. However, as it seeps through the ground it comes into contact with rocks and dissolved compounds from them. These compounds often contain calcuim and magnesium ions, which CAUSE HARD WATER
- Anyone living in a hard water area will notice that the water doesnt easily form lather with soap. Instead, a grey scum is formed so more soap is needed to form a lather. In areas where there is soft water there are no dissolved compounds.
CALCIUM IONS FROM WATER+STERATE IONS FROM SOAP= CALCIUM STERATE(scum)
PERMANENT hard water= remains hard when boiled
TEMPORARY hard water= is softened by boiling because it contains an additional hydrogencarbonate ion. They decompose when you heat them which then react with the calcium or magnesium to form solid calcium carbonate.
Cleaning our water
When we take water from rivers and reserves we give them treatment in a water treatment facility. This treatment involves several physical and chemical processes. The water source is chosen so that it contains as few dissolved particles as possible. The water passes through 5 stages:
- The water is passed through a filter make of sand which removes particles of mud or grit.
- It then passes through a screen made from bars of metal placed close together. These catch large objects such as leaves or twigs.
- Then it passes through a settlement tank where the sand and soil settle out.
- Then Aluminuim sulfate and lime are added to the water. Small particles of dirt clump together so that they sink to the bottom of the water. The sludge that collects like this is dumped at a landfill.
- Although the water now looks clean, it may still contain harmful bacteria so a small amount of chorine is added to kill them.
- Finally, the pH of the water is checked and corrected so that it is neutral, so the water is stored in large tanks or reserves ready to be pumped into the community.
Fuel is something that releases energy when being burned through combustion. It is measured in JOULES.
Qualities of a good fuel:
- viscosity; correct state, temperature alters viscosity.
- flammable; to release energy, combustion, activation energy
- efficient; releases a lot of energy per gram
- high chemical bond energy
- supply and demand/not finite
- environmental impact
Global Dimming= carbon particles in the air blocking the sunlight
Moles= mass(a) divided by relative atomic mass
Energy Release= mass of water heated x specific heat capacity x rise in temp.
If heat is GIVEN OUT this energy must have come from chemical energy in the reactants. Reactants transfer chemical energy to heat energy,so the temperature rises.
Endothermic Reactions are more rare. A few reactions that give off gases are highly endothermic, they get very cold and temperature drops. Reactants convert heat energy to chemical energy.
Breaking Chemical Bonds
Most chemicals will decompose(break up) if we heat them strong enough. This indicates that breaking chemical bonds requires energy and is an ENDOTHERMIC PROCESS
Making Chemical Bonds
Energy will be given out in an exothermic process when bonds are formed,
When the energy from bond forming exceeds that needed for the bond breaking the reaction is exothermic and vise versa.
We use analytical techniques to:
- Identify presence or absence of an element or compound (QUALITITATIVE ANALYSIS)
- Measure some feature of a substance i.e the amount of C in C6H1206; concentration of an acid(QUANTITATIVE ANALYSIS)
Litium Chloride- Red
Sodium Chloride - Orange
Potassium Chloride -Pink/Purple
Copper Chloride - Green/Blue
Calcium Chloride - Yellow/Red
Barium Chloride - Pale Green
Titrations are used to measure accurately how much alkali is needed to react completley with a known amound of acid.
Titrations are used for the neutralisation reactions and the point at which neutralisation is complete is called the end point.
Hydrogen in ACIDS releases HYDROGEN ions. The stronger the acid, the more it releases hydrogen ions.
ALKALIS release HYDROXIDE ions, so when acids and alkalis mix the hydrogen and hydroxide ions produce H2O or water showing neutralisation.
PHENOPHTHALIEN - Indicator; Alkali - Pink; Neutral - Colourless; More effective than Universal Indicator because you can detect between the different pH's.
Ammonia(NH3) is an important chemical with many uses, one being in the production of Nitrogen rich fertilisers. Due to its importance NH3 is produced on an industrial scale through the Haber Process, a CHEMICAL REACTION that is carefully controlled to maximise output while minimising costs. Nitrogen is a very unreactive gas which tends to react slowly if at all. Changing the element Nitrogen into compounds that plants can absorb involves reacting it with HYDROGEN.
NITROGEN+HYDROGEN = Ammonia (REVERSABLE REACTION)
Ways to speed up this reaction:
- Use an Iron catalyst
- High temp. 450 Degrees
- Pressure of 100 atmospheres
Refers to the reactions of CARBON based compounds. An example of this would be the hydrocarbon alkenes and alkanes. There are other functional groups which are also charecterised by their molecular structure, a functional group is a combination of atoms that exist as one unit within a bigger structure:
- Alcohol: An alcohol molecule is replacing the H molecule of an alkene to an O-H molecule. The -OH group of atoms is an example of a functional group
- Carboxylic Acid: Etanoic acid is the main acid in vinegar. All carboxylic acids contain the -COOH functional group.
- Esters: They are closely related to carboxylic acids. If we replace the H atom in the -COOH group by a hydrocarbon group we get an ester.
Methanol, Ethanol and Propanol are the first 3 alcohols in the homologous groups. They all:
- Have the -OH functional group
- Dissolve in water to form a neutral solution
- Act as solvents
- React with Na to produce H2
- Burn easily to be used as fuel