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Chem Paper 1 (C4 - Chemical Changes (The Reactivity Series (The Series…

- - - - There are oxidation reactions, where electrons are lost.
      - There are reduction reactions, where electrons are gained.
      - Reduction reactions involve the loss of oxygen atoms.
    - - Copper
      - Iron
      - Hydrogen
      - Lead
      - Tin
      - Zinc
      - Carbon
      - Aluminium
      - Magnesium
      - Calcium
      - Sodium
      - Potassuim
  - - - Have the solution of unknown solution in a conical flask.
      - Add a solution of known concentration until it has neutralised the one in the flask (can be seen using an indicator).
      - Using the ratio of volumes required, the concentrations follow the same ratio so can work out the concentration of the unknown solution.
  - - - This process is called electrolysis.
      - When ionic compounds are melted or dissolved in water, the ions become free to move around.
      - These liquids or solutions are able to conduct electricity and are called electrolytes.
      - Passing a current through the electrolyte causes the ions to move to the electrodes.
      - Positively charged ions move to the cathode, negative ions move to the anode.
    - - Cathode
        
        Hydrogen is produced if the metal is more reactive than hydrogen.
        
        Otherwise the metal is always produced here.
      - Anode
        
        Oxygen is produced unless halide ions are present in the solution.
        
        Otherwise the halogen in solution will be discharged at the anode.
    - - Cathode
        
        Always reduction reactions as ions are gaining electrons.
      - Anode
        
        Always oxidation reactions as ions are gaining electrons.
    - - 2H + 2e- ---> H2
      - 4OH- - 4e- ---> O2 + 2H2O
- - - - Before electrons were discovered, atoms were believed to be just tiny spheres of matter
    - - The nucleus was a ball of positive charge with negative charges embedded into the surface
    - - The nucleus was actually tiny - only 1/10,000th of the atom's diameter - surrounded by electrons (first thought to orbit at random distances) found to be orbiting at specific orbitals / energy levels
- - - - Occurs between a metal and a non-metal. This is because metals form + ions and non-metals form - ions, so there is a force of attraction between them.
      - Ionic substances for giant ionic lattices which have very high melting points. These structures also have a very low electrical conductivity as there are no free electrons to carry the charge.
      - However, when dissolved in water or melted, the individual ions are free to move around - allowing them to carry a charge and thus conduct electricity. This is the foundation principle of electrolysis.
    - - Covalent bonds form solely between non-metals. There are two types of covalent molecules; small covalent molecules and giant covalent molecules.
      - Small covalent molecules have a low melting and boiling point as - although the intramolecular forces are strong - the intermolecular forces are weak, and it is these that are broken in the process of melting or boiling a substance. SCM's are often gases at room temperature (H2) and do not conduct electricity.
      - Giant covalent molecules have very high melting and boiling points as all the atoms are joined together by intramolecular covalent bonds, which are very strong. Also, they are very hard and do not conduct electricity.
    - - Metallic bonds form purely between metal atoms. Each atom 'donates' electrons to the sea of delocalised electrons which causes a force of attraction between all of the metal ions, forming a very strong molecule. Metals have very high melting and boiling points, as well as being malleable in their pure forms due to the uniformity of their structure.
      - The sea of delocalised electrons allows for metals to be great conductors of electricity, as each of the electrons can move freely, carrying a charge flow.
  - - - Solids
        
        Solids have a generally uniform structure in the particle model, with none of the particles being able to move more than jiggle a bit.
        
        Solids are considered uncompressable.
        
        Particles in a solid have a very low internal energy store.
      - Liquids
        
        Particles in a liquid have a slightly higher internal store of energy, and are thus free to move around more as some of the bonds joining them are broken.
        
        Liquid versions of materials take up more room than the solid version - the exception being ice and water.
      - Gas
        
        Gases have a high internal store of energy and are thus completely free to move around. They mover around randomly and take up the most room per unit of mass of any of the states of matter.
      - Plasma
        
        Plasma is essentially ionised gas, where the individual atoms have lost some of their electrons. This results in a mixture of positive ions and negative electrons. If the plasma loses heat, the ions and electrons reform into a gas.
      - Antimatter
        
        Antimatter is a strange substance we don't yet fully understand. However, we know that each subatomic particle of an antimatter atom has the exact same mass as it's normal matter counterpart (or partner), with the opposite electric charge. So an electron is 1- charge, and a positron is 1+.
  - - - Anything that is 1-100nm in size is a nanoparticle
      - Nanoparticles have different properties to the bulk version of the same material as the surface area to volume ratio is so huge.
      - Often, smaller amounts of nanoparticles are needed than bulk materials to be effective.
    - - Fine particles have diameters between 100 and 2500nm
      - Coarse particles are anything between 0.0000025m and 0.00001m.
- - - - Exothermic
        
        Combustion
        
        Oxidation
        
        Neutralisation
      - Endothermic
        
        Thermal Decomposition
        
        Reaction of citric acid with sodium hydrogen carbonate
  - - - Non-rechargeable have reactions that are not reversible.
      - Batteries consist of many cells joined together for a greater voltage.
      - Voltage produced by a cell is determined by many factors including the electrodes and the electrolyte.
      - Cells contain chemicals that react to produce electricity.
    - - Fuel cells are supplied from an external source.
      - Fuel is oxidised electrochemically within the cell to produce a potential difference.
      - Hydrogen fuel cells include the oxidation of hydrogen to produce water and may be an alternative to other fuel cells in the future.
- - - - 1) Use a pH indicator (universal indicator) to analyse the pH of the water sample.
      - 2) Heat up a set volume of the water to 100 degrees centigrade so the water boils.
      - 3) Collect the now pure water in a liebig condenser and have it output into a beaker.
      - 4) When all the water has evaporated from the conical flask, measure the mass of the solid that remains behind to find the amount of dissolved solids in the sample (and thus its initial purity).
    - - Hot equipment (bunsen burner) so tie up hair and be careful around the flames and hot beakers.
  - - - 1) Wash and rinse a graduated pipette with the known alkali and use it to measure out an accurate amount of the known alkali solution into a conical flask.
      - 2) Add a suitable indicator (e.g. phenolphthalein) and place flask on a white tile so the colour can be easily seen.
      - 3) Place the acid into a burette that has been carefully washed and rinsed with the acid. Fill it up to the zero centimetre cubed mark.
      - 4) Slowly add the acid and swirl until the indicator changes colour (just), this is called the end point. Take a note of the amount of acid used to neutralise the alkali.
      - 5) By using the ratio of volumes of the acid and alkali, you can work out the ratio of the concentrations; working out the acid's concentration.
    - - Using corrosive chemicals so need to use eye and skin protection and clear up any spillages immediately.
  - - - Method
        
        1) Add metal oxide/carbonate to a warm acid solution until no more will react.
        
        2) Filter the excess metal oxide/carbonate off to leave a salt solution.
        
        3) Gently warm the solution in a crucible until it starts to evaporate. Evaporate about 1/2 of the solution this way then leave it overnight to allow the rest to evaporate at room temp.
        
        4) Harvest the new soluble salt crystals left behind.
      - Hazards and Risks
        
        Corrosive materials/chemicals so need PPE such as safety glasses and clear up any spills instantly.
        
        Hot water bath or a bunsen burner so don't have hair down and be careful around hot equipment.
      - Title: Preparation of a pure, dry sample of a soluble salt from an insoluble oxide or carbonate.
    - - Title: Investigating what happens when an aqueous solution is electrolysed using inert electrodes.
      - Method
        
        1) Set up two electrodes over a beaker with the aqueous solution in it.
        
        2) Pass an electrical current through the electrodes (through the aqueous solution).
        
        3) Observe what products are formed at each of the electrodes.
      - Hazards and Risks
        
        A low voltage must be used to prevent a dangerous electric shock.
        
        The room must be well ventilated as some of the products may be dangerous if exposed to for too long (such as chlorine gas). For the same reason, the experiment must only be conducted for a short space of time.
  - - - 1) Set up a beaker with HCl in it and a thermometer.
      - 2) Add the metal powder and stir until the reaction is complete and record the highest temperature the reaction reached.
      - 3) Calculate the temperature change for the reaction.
      - 4) Repeat with different metals.
    - - There should be a correlations between the reactivity of the metal and the temperature change.
      - There will always be a degree of uncertainty in the recording of the results - should repeat each reaction three times and take an average (excluding any anomalies).
    - - Low risk of corrosive acids so PPE such as safety glasses must be worn and spills immediately cleaned up.
    - - The independent variable is the metal used in the reaction.
      - The dependant variable is the temperature change over the course of the reaction.
      - The control variables are: the type of acid, the concentration of the acid, the volume of the acid and the external temperature in the lab.