CHEMICALS IN THE ATMOSPHERE
0.04% CARBON DIOXIDE
The atoms within the molecules are held together by very strong covalent bonds
The forces of attraction between these molecules are very weak
You only need a bit of energy to overcome the weak forces between the molecules
So they have low melting and boiling points
They're usually gases and liquids at room temperature
Pure molecular substances don't conduct electricity because there are no free electrons or ions
Covalent bonding is where atoms share electrons with other atoms to form full shells
COVALENT: Non-metals & non-metals (&shares electrons)
IONIC: Metals & non-metals (&takes or gives electrons)
CHEMICALS IN THE HYDROSPHERE
THE EARTH'S HYDROSPHERE IS THE OCEANS
The Earth's hydrosphere consists of oceans, puddles, lakes ect.
It also contains any compounds that are dissolved in water
Many of these compounds are SALTS (Group1 & Group7 compounds)
CHEMICALS IN THE HYDROSPHERE
SOLID IONIC COMPOUNDS FORM CRYSTALS
Ionic compounds are made of ions
Ions with opposite charges are strongly attracted to one another & a GIANT LATTICE of ions builds up
There are ionic bonds between all of the ions
A single crystal of salt is one GIANT IONIC LATTICE
CHEMICALS IN THE HYDROSPHERE
IONIC COMPOUNDS HAVE HIGH MELTING & BOILING POINTS
The forces of attraction between the ions are very strong
It takes a lot of energy to overcome these forces and melt the compound, even more to boil it
This makes them SOLIDS at room temperature
ELEMENT COLOUR FLAME
When two solutions react to form an insoluable solid compound called a precipitate
ADD SODIUM HYDROXIDE:
"METAL" COLOUR OF PRECIPITATE
IRON (II) GREEN
IRON (III) REDDISH BROWN
TESTING FOR CARBONATES
You can test for carbon dioxide using limewater
Bubble carbon dioxide through a test tube of limewater and if it goes cloudy you've identified a carbonate ion
TESTING FOR SULFATES
ADD DILUTE HYDROCHLORIC ACID (TO GET RID OF ANY TRACES OF CARBON) FOLLOWED BY BARIUM CHLORIDE SOLUTION
A WHITE PRECIPITATE OF BARIUM SULFATE MEANS THE ORIGINAL COMPOUND WAS A SULFATE
TESTING FOR HALIDES
ADD DILUTE NITRIC ACID (TO GET RID OF CARBONATE IONS) FOLLOWED BY SILVER NITRATE SOLUTION
HALIDE COLOUR PRECIPITATE PRECIPITATE
CHLORIDE WHITE SILVER CHLORIDE
BROMIDE CREAM SILVER BROMIDE
IODIDE YELLOW SILVER IODIDE
CHEMICALS IN THE LITHOSPHERE
THE LITHOSPHERE IS THE EARTH'S RIDGID OUTER LAYER - THE CRUST AND PART OF THE MANTLE BELOW IT
DIFFERENT TYPES OF ROCK CONTAIN DIFFERENT MINERALS AND ELEMENTS
The carbon atoms in diamonds each form four covalent bonds in a very rigid covalent structure
This structure makes carbon the hardest natural substance
All the strong covalent bonds give diamond a VERY HIGH MELTING POINT
It doesn't conduct electricity because it has no free electrons
It's insoluable in water
Graphite is made from carbon and has a giant covealent structure.
Each carbon atom forms three covalent bonds, creating sheets of carbon atoms which can slide over eachother. This means graphite is slippery, so it's useful as a lubricant.
The layers are held together so loosely that they can be rubbed off on to paper and leave a black mark (how pencils work).
Graphite has a HIGH MELTING POINT
Only 3 of carbon's 4 outer electrons are used in bonds, so there are lots of spare electrons - conducts electricity - used for electrodes.
Most of the silicon and oxygen in the Earth's crust exists as the compound silicon dioxide
Silicon dioxide is what sand is made of
Each grain of sand is one giant structure of silicon and oxygen
It has similar properties and structure to a diamond, e.g. high melting point & doesn't conduct electricity
METALS FROM MINERALS
Metal ores are rocks that contain minerals from which metals can be extracted & in many cases the ore is an oxide of the metal.
Most metals need to be extracted from their ores using a chemical reaction, but a few unreactive materials, such as gold, are found in the Earth as the metal itself.
More reactive metals are harder to extract.
A common way of extracting metal from its ore is chemical reduction using CARBON or CARBON MONOXIDE
When an ore is reduced, OXYGEN is removed
When a metail oxide loses its oxygen it is REDUCED & the carbon gains the oxygen and is OXIDISED
Metals that are more reactive than carbon can't be extracted by reduction and must be extracted by electrolysis
Electrolysis is the decomposition of a substance using electricity.
It needs a liquid to conduct the electricity - the electrolyte (usually free ions dissolved in water or molten ionic compounds).
Electrons are taken away from ions at the positive electrode and given to other ions at the negative electrode.
As ions gain or lose electrons they become atoms or molecules.
RELATIVE ATOMIC MASS - (top left number on element square)
RELATIVE FORMULA MASS - relative atomic masses added together
They can also be used to work out how much metal can be extracted from a ore.
Metal ions consist of a giant structure.
Metallic bonds involve free electrons which produce all the properties of metals.
These free electrons come from the outer shell of every metal atom in the structure.
The positively charged metal ions are held together in a crystal by a sea of free electrons that can move.
1) THEY'RE GOOD CONDUCTORS OF HEAT & ELECTRICITY
2) MOST METALS ARE STRONG & MALLEABLE - Metallic bonds mean metals have a high TENSILE strength (they're strong & heard to break)
3) THEY GENERALLY HAVE HIGH MELTING & BOILING POINTS - They're very strong so it takes a lot of energy to break them.
There is a limited amount of ores and people have to balance the social, economic and environmental effects of mining the ores.
Mining metal ores is good because useful products can be made and it provides jobs and brings money in to the economy.It also means that services such as health can be improved.
Mining ores is bad for the environment though as it uses a lot of energy, scars the landscape and destroys habitats. Deep mine shafts can also be dangerous for a long time after the mind has been abandoned.
Mining and extracting metals takes a lot of energy, mostly from burning fossil fuels.
Fossil fuels are running out so it's important to conserve them & burning them contributes to global warming, acid rain and climate change.
Recycling saves money too, because energy isn't cheap.
There is a finite amount of metal in the Earth and recycling conserves these resources.
Recycling metal cuts down the amount of rubbish that gets sent to landfills, which saves spaces and prevents pollution.