Chem Unit 1

Chem Unit 1

1. C1.1

   • Atoms
     • All substances are made from atoms
       • A substance made from only one type of atom is called an element
     • Each atom has its own chemical symbol
     • Each atom has it's own different charge
       • Proton = +1
       • Neutron = neutral
       • Electron = -1
     • There are always an equal number of protons and electrons
       • Atoms have no overall electrical charge
     • The number of protons in an atom is its atomic number
       • The sum of protons and neutrons is its mass number
     • Electrons are in energy levels around the nucleus of an atom
       • In the first energy level there are only a maximum two electrons
         • In all the others there are a maximum of eight
   • Periodic table
     • Elements in the same group of the periodic table have the same number of electrons in their out energy level
     • Elements in group 0 are called nobel gasses
       • They are very unreactive
       • All of their outer energy levels are full
   • Chemical reactions
     • When elements react, their atoms join with other atoms to form compounds
       • This involves giving, taking or sharing electrons
     • Chemical reactions can be represented by word or symbol equations
     • No atoms are lost or made during a chemical reaction
       • Meaning the mass of the products equals the mass of the reactants

2. C1.2

   • Calcium carbonate
     • Lime stone is mainly composed of valium carbonate
       • CaCO3
     • Calcium carbonate can be decomposed by heating (thermal decomposition)
       • This produces calcium oxide and CO2
     • The carbonates of magnesium, copper, zinc, calcium and sodium decompose on heating in a similar way
     • When calcium oxide is mixed with water calcium hydroxide is produced
       • This is an alkali that can be used to neutralise acids
       • Also known as limewater
         • Limewater can be used as a test for CO2
           • If it turns cloudy CO2 is present
     • When calcium hydroxide is mixed with CO2 calcium carbonate is created
     • When CaCO3 is mixed with acids CO2, salt and water are produced
     • Heated Limestone makes cement
       • Cement is mixed with sand to make mortar
       • Cement is mixed with sand and aggregate to make concrete

3. C1.3

   • Extracting metals
     • Metals are only extracted from their ore if there is enough of the metal in it
     • Ores are mined and may be concentrated before the metal is extracted from them
     • Most unreactive metals are found as metals not ores
     • Metals that are less reactive than carbon are extracted via reduction
     • Metals that are more reactive than carbon are extracted via electrolysis
     • Copper
       • Copper can be extracted by phytomining or by bleaching
       • Copper can be obtained from solutions of copper salts by electrolysis or by displacement using scrap iron
     • We should recycle materials as we have limited resources, it uses a lot of energy and it effects the environment
   • Alloys
     • Iron
       • Iron from a blast furnace contains about 96% iron
         • Its impurities make it brittle
       • Most iron is converted into steel
     • Alloys are used as pure metals are too soft
   • Properties and uses of metals
     • ls are good conductors of heat and electricity and can be bent into any shape
     • Copper has properties which make it useful for electrical wiring and plumbing