Chemistry Of The Elements

• Elements of the same family react in a similar way
• When lithium, sodium and potassium are put into water, they all react vigorously
• The reaction produces a METAL HYDROXIDE SOLUTION
• It is alkaline, this is why group 1 metals are known as the Alkali Metals
• The reaction of the alkali metals with water also produces hydrogen

SODIUM + WATER > SODIUM HYDROXIDE + HYDROGEN

2Na(s) + 2H20(l) > 2NaOH(aq) + H2(g)

• As you go down the group, they become MORE REACTIVE
  
• The elements in group 1 get MORE REACTIVE as the ATOMIC NUMBER INCREASES
• All group 1 metals have 1 electron in their outer shell
• As you go down, the outermost electron is in a shell thats further from the nucleus 
• This means the attraction between the outermost electron and nucleus become less
• So as you go down group 1, the atoms get bigger, the outer electron is more easily lost, and the metals are more reactive.

• The properties of the elements in Group 7 change gradually as you go down the group
• As the atomic number of the halogens increase, the elements have a darker colour and a higher boiling point 
• The higher up, the more reactive 
• This is because the shell with the missing electron is nearer to the nucleus, so the pull from the positive nucleus is greater

Hydrogen Chloride Gas Dissociates in Water

• Halogens combine with hydrogen to form hydrogen halides, for example hydrogen chloride and hydrogen bromide.
• Hydrogen chloride has the chemical formula HCL and is a gas at room temp
• When HCL dissolves in water, the molecules split up into H+ ions and Cl- ions 
• The solution that is formed is called hydrochloric acid
• Its acidic because it contains H+ ions

Halogens are all one electron short of having a full outer shell

• The elements in Group 7 take part in displacement reactions
• A more reactive element pushes out the less reactive element from a compound

Halogen Displacement Reactions Involve Transfer Of Electrons

e.g Cl2(aq) + 2KI(aq) > I2(aq) + 2KCI(aq)

e.g Cl2(aq) + 2I-(aq) > 2Cl-(aq) + I2(aq)

• When this reaction happens, electrons are passed from the iodine to the chlorine 
• A loss of electrons is called oxidation
• A gain in electrons is called reduction
• Reduction and oxidation happen simultaneously e.g, if chlorine is reduced, iodine is oxidised.
• An oxidising agent accpets electrons and gets reduced. Here, chlorine is the oxidsing agent
• A reducing agent donates electrons and gets oxidised. Here, iodine is a reducing agent

Acid + Metal > Salt + Hydrogen

• The more reactive the metal, the faster the reaction will go
• The speed of reaction is indicated by the rate at which the bubbles of hydrogen are given off
• The hydrogen is confirmed by the burning splint test

Magnesium

• Reacts vigorously with cold dilute acids and produces loads of bubbles

Aluminium

• Aluminium doesnt react much with cold dilute acids because it has a protective aluminium oxide  layer. But, it reacts vigorously with warm dilute acids and produes lots of bubbles

Zinc and Iron

• Both zinc and iron react slowly with dilute acids but more strongly if you heat them up

The Name of the Salt Depends On The Metal and Acid Used

• Metals react with dilute HCl and sulfuric acid in the same way, but different salts are formed depending on the acid used
• HCl will always produce chloride salts

Hydrochloric acid + magnesium > Magnesium chloride + hydrogen

• Sulfate acids will always produce sulfate salts

Sulfuric acid + magnesium > magnesium sulfate + hydrogen

Metals also React with Water

METAL + WATER > METAL HYDROXIDE + HYDROGEN

POTASSIUM

SODIUM                     Very Reactive

LITHIUM

CALCIUM

MAGNESIUM             Fairly Reactive

ALUMINIUM

ZINC

IRON                          Not Very Reactive

COPPER

SILVER/GOLD           Not Reactive At All

Iron and Steel Corrode to Make Rust

• Iron rusts easily with oxygen (from the air) and water.
• The chemical reaction that takes place when iron corrodes is an oxidation reaction
• The iron gains oxygen to form iron(III) oxide
• Water then becomes loosely bonded to the iron(III) oxide 

iron + oxygen + water > hydrated iron(III) oxide (rust)

There are 2 Main Ways to Prevent Rusting

Barrier Methods:

• Painting/Coating with plastic ,ideal for big and small structures alike
• Oil/ Greasing, has to be used when 2 moving parts are involved

Sacrificial Methods:

• Zinc is more reactive than iron, so it will be oxidised instead of iron
• A zinc coating can be sprayed onto the object, known as galvanising 

• 78% NITROGEN
• 21% OXYGEN
• 1% ARGON
• 0.04% CARBON DIOXIDE 

Using Copper to Investigate the Proportion of Oxygen in the Atmosphere

• When heated, copper reats with oxygen in the air to make copper (II) oxide, so the reaction uses up oxygen
• If you heat excess of copper in a tube and pass air over it using 2 syringes, using markers to tell how much oxygen has been used up.

2Cu + O2 > 2CuO

• If you start with 100cm3 of air, youll end up with about 80cm3 when the reaction is finished and the air has cooled.
• If 20cm3 has gone, then around 20% of the air must be oxygen

• Hydrogen peroxide will decompose into water and oxygen

2H2O2 > 2H2O + O2

• This decomposition is really slow but the rate of reaction can be increased with a sprinkle of manganese (IV) oxide catalyst
• You can collect the oxygen produced over water

When you Burn Something It Reacts With Oxygen In The Air

• Magnesium: burns with a bright white flame in air and the white powder forms is magnesium oxide. It is slightly alkaline when dissolved in water.
• 2Mg + O2 > 2MgO
• Carbon: Will burn in air if its strongly heated. Orangey/Yellow flame and produces carbon dioxide gas. Carbon dioxide produced, its slightly acidic when dissloved in water
• C + O2 > CO2
• Sulfur: Sulfur burns in air or oxygen with a pale blue flame and produces sulfur dioxide and slightly acidic when dissolved in water
• S + O2 > SO2

Collecting Gases in a Test Tube

• The delivery tube is fed directly into a test tube either upwards or downwards
• Use upward delivery to collect 'lighter than air' gases (e.g. H2)
• Use downward delivery to collect 'heavier than air' gases (e.g CO2, Cl2)

Dilute Acids with Calcium Carbonate to produce CO2

• The calcium carbonate (marble chips) is put in the bottom of a flask and HCl is added
• The dilute HCl reacts with calcium carbonate, water and carbon dioxide gas

2HCl + CaCO > CaCl + H2O + CO2

• The carbon dioxide gas is collected in a gas syringe or using downward delivery 

Thermal Decomposition of Metal Carbonates AlsoProduces CO2

• Another way of making CO2 is by heating a metal carbonate, an example of thermal deccomposition, when the substance breaks down into simpler substances when heated.

e.g CuCo > CuO + CO2

CO2 is used in Fizzy Drinks...

• CO2 is used in carbonated drinks to make them fizz
• The CO2 is slightly soluble in water and dissolves into the drinks when under pressure. This produces slightly acidic solution due to the formation of carbonic acid.

CO2 + H2O > H2CO3
Carbon Dioxide + Water > Carbonic Acid

...And Fire Extinguishers

• Carbon dioxide is more dense than air - so it sinks onto the flames and stops the oxygen the fire needs getting to it
• Carbon dioxide extinguishers are used when water extinguishers arnt safe, with electrical fires.

Carbon Dioxide is a Greenhouse Gas...

• The temperature of the Earth is a balance between the heat it gets from the sun and the heat it radiates back to space
• Gases in the atmosphere like CO2, methane and water vapour naturally act like an insulating layer.
• They absorb most of the heat that would normally be radiated out into space, and re- radiate it in all directions - including back towards Earth.

Carbon Dioxide in the Atmosphere is Increasing

• Deforestation: fewer trees means less CO2 is removed via photosynthesis
• Burning Fossil Fuels: Carbon that was 'locked up' in these fuels is being released as CO2

Flame Test Identify Metal Ions

Lithium: Crimson flame
Sodium: Yellow/Orange flame
Potassium: Brick red flame

• To do this test you need a clean platinum wire by dipping it into some HCl and holding it in a flame until it burns without colour, then dip it into the sample

Some Metals Form a Coloured Precipitate with NaOH

Copper(II), Cu2+: Blue > Cu2+(aq) + 2OH-(aq) > Cu(OH)2(s)

Iron(II), Fe2+: Green > Fe2+(aq) + 2OH-(aq) > Fe(OH)2(s)

Iron(III), Fe3+: Reddish Brown > Fe3+(aq) + 3OH-(aq) > Fe(OH)3(s)

Ammonium Compound gives of Ammonia

Damp Litmus paper: Red to Blue

• It is damp so the ammonia gas can dissolve and make the colour change 

Hydrochloric Acid is used to detect Carbonates

• To test for carbonates, add dilute HCl to your test sample.
• If carbonates (CO3 2-) are present then carbon dioxide will be released

CO3 2- + 2H+ > CO2 + H2O
Carbonate + Acid > Carbon Dioxide + Water

Test for Sulfates with HCland Barium Chloride

• Sulfate ions (SO4 2-) produce a WHITE PRECIPITATE
• To test for a sulfate ion, add dilute HCl, followed by Barium Chloride Solution
• Ba 2+ + SO4 2- > BaSO4

Test for Halides (Cl-,Br-,I-) with Nitric Acid and Silver Nitrate

• Chloride ion: White precipitate of silver chloride > Ag+ + Cl- > AgCl
• Bromide ion: Cream precipitate of silver bromide > Ag+ + Br- > AgBr
• Iodine ion: Yellow precipitate of silver iodide > Ag+ + I- > AgI

Chlorine

• Chlorine bleaches damp litimus paper, turning it white

Oxygen

• Oxygen relights a glowing splint

Carbon Dioxide

• Carbon dioxide turns limewater cloudy 

Hydrogen

• Makes a squeeky pop with a lit splint

Ammonia

• Turns damp red litmus paper blue (+smell)

Wet Copper(II) Sulfate is Blue - Dry Copper(II) Sulfate is White

• Copper(II) sulfate can be used to test for water
• When copper(II) sulfate is bound to water, it forms blue crystals.
• If you heat the blue hydrated copper (II) sulfate crystals it drives the water off 
• This leaves a white anydrous copper (II) sulfate powder, which doesnt have any water bound to it
• If you then add a couple of drops of water, the blue crystals will be back again

This test will tell you if water is present in a solution, but wont tell you if the water is pure.

The Purity ofWater

• When a substance is pure, it is only made up of one substance
• Pure water will always boil at 100 degrees celsius and Freeze at 0 degrees celsius
• If it doesnt, the sample isnt pure