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Chemistry

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Chemistry

Atoms and Elements
- The building blocks of everything
- What is inside?
  - The nucleus is the middle of the atom
    - Contains protons and neutrons
      - Neutrons; 0 charge
      - Protons; + charge
  - The electrons move around the nucleus; they have a - charge
- Always equal
  - There is no overall charge
  - The charge of the protons and electrons cancel each other out
    - Hence, there is always equal amounts of protons and electrons
  - Otherwise if it is unequal it is becomes charge, called an ION
- Elements
  - The number of protons in the nucleus decides what element it is
  - Elements consist of ONLY one type of atom
The Periodic Table
- A table full of all the elements
- Atoms are represented by symbols
  - EG
    - C= carbon
    - O= oxygen
    - Pb= lead
    - Fe= iron
- Atoms with similar properties are in the same columns
  - The columns are labeled in groups
    - All of the elements in that group have the same electrons in their shells
- Group 0
  - Noble gases
  - They have a full outer shell; making them unreactive/ stable
- Why do elements react?
  - They react if they don't have a full outer shell, so they react to gain more electrons
- How to work out electrons protons and neutrons?
  - Number of protons and electrons
  - Total number of protons and neutrons
    - To find out the neutrons subtract one from another
Electronic shell
- Electrons occupy the outer shells of atoms
- They fill up from inwards to outwards
- Each shell can only contain a certain amount of electrons
  - 1st Shell= 2
  - 2nd Shell= 8
  - 3rd Shell = 8
- Atoms always want a full outer shell and react with other elements to gain electrons
- You write them seperating with a ,
  - EG
    - Nitrogen has 7 electrons so...
      - electronic structure = 2,5
Balancing equations
- Atoms are never lost just used over and over again.
- There needs to be an equal amount on both sides as you don't loose anything
- The start (reactants)
- The end (the product)
- EG
  - Magnesium + Oxygen - magnesium oxide
  - 2 Mg + 02 - 2Mg0
Compounds
- Atoms join together to make compounds
  - Chemically bonded
  - Difficult to separate out again
- What are they?
  - Giving and sharing of electrons make the reaction
    - ONLY THE ELECTRONS INVOLVED NOT THE NUCLEI
- IONS
  - If formed from a metal and non- metal consists of IONS
  - THE METAL ATOMS lose electrons to form positive charge ions
  - THE NON- METAL ATOMS gain electrons to form negative charged ions
    - The opposite charges mean they are strongly attracted to each other called IONIC BONDING
      - IONIC BONDING
        Positive and negative ions attract one another and bind together forming a new substance. This is called ionic bonding.
- COVALENT BONDS
  - A compound formed from non-metals
  - Share electrons
- The properties are totally different then the elements
Lime Stone
- What is Lime Stone?
  - It is mainly calcium carbonate (CaCO3)
    - Reacts with acid to form calcium salt, carbon dioxide and water.
      - The type of salt depends on the acid used
- Where does it come from?
  - It is quarried out of the ground
- Thermal Decomposition
  - Thermal decomposition is when one substance chemically changes into at least two other substances
  - When Calcium Carbonate is thermally decomposed it becomes calcium oxide and carbon dioxide
    - Magnesium, copper and zinc act in the same way
  - Need a high temperature to thermally decompose something.
- Calcium oxide and water
  - Forms calcium hydroxide
    - Ca0+ H20 -- Ca(OH)2
    - Alkali metal
    - Neutralise acidic soil
    - Test for carbon dioxide
      - Lime water test
        If the solution goes cloudy when gas is bubbled through then carbon dioxide is present
- Uses
  - Heated to make cement
    - Cement mixed with sand and water to make MORTAR
      - Attach bricks together
    - Cement and aggregate to make CONCRETE
- Issues
  - Huge ugly holes left behined
  - Destroys habitats
  - Quarrying - noise and dust
  - Transportation- noise pollution
  - Energy is need - burning fossil fuels
  - Cement factories- dust - breathing problems
- On the plus side
  - Produces useful things
  - Some chemicals use limestone
  - Can neutralise things
  - Provides jobs
    - Economy
  - When finished the landscape is usually fixed
  - Cheap
  - Easy to cut
  - Hard wearing
  - Quick way of construction
  - Doesn't rot like wood
  - Can't be eroded by insects
Getting metal from rocks
- Ores
  - An ore is a rock which contains enough metal to make it worth while extracting
  - The ore is an oxide of metal
  - Metals are extracted using chemical reactions
  - The profitability changes over time
    - Market price may change
    - Technology improvements
  - How are they extracted?
    - Chemically, reduction or by electrotysis
      - If they are more reactive then you use electrotysis
        Eg: Copper
        Purified by electrotysis but uses carbon to remove the oxygen
      - Expensive process- uses a lot of energy
      - Using carbon to remove the oxygen
        Called SMELTING
      - Needs to be less than Carbon in the REACTIVE SERIES
      - Breaking down of a substance using electricity
      - liquid to conduct the electricity; called electrolyte
        Made from metal salt solutions
        Has free ions
        These conduct electricity
        Electrons are taken away by anode
- Displacement
  - More reactive metals react more vigorously
  - When a metal is put in a dissolved metal compound the stronger metal replaces the weaker one in the compound
  - Copper sulfate + iron - iron sulfate + copper
  - If you want to get a metal out of a compound this is the method
- PROS
  - Useful products can be made
  - Jobs - Economy
- CONS
  - Noise pollution
  - Mind shafts can be dangerous
- Why recycle ?
  - Extraction uses fossil fuels
  - Global warming
  - Saves money
  - Less rubbish for land fill; less pollution
Metals
- Properties of meatals
  - Strong but can be bend and hammered into different shapes
    - Good for bridges and car bodies
  - Good conductors of heat
    - Saucepans
  - Conduct electricity well
    - Electrical wires
  - Metal fatigue is when they are stresses and strains are repeated on them
- Specific metals
  - Copper
    - Conducts electricity
    - Durable
    - Doesn't react with water
  - Aluminium
    - Corrosion resistance
    - Low density
    - Forms strong alloys
  - Titanium
    - Very strong
    - Corrosion resistant
- Alloys
  - A metal made by combining two or more metallic elements
  - The mixing of metals gives it different properties
  - Makes them harder to slide over each other
  - Bronze = copper + tin
- Pure metals atoms move easily as it is all one pattern so they can be bent easily