Chemistry

• Atom


  the smallest particle of an element that can exist
• Element


  contains only one type of atom
• Molecule


  two or more atoms that are chemically bonded together
• Compound


  two or more different elements that are chemically bonded together in fixed proportions
• Mixture


  two or more different substances that are not chemically bonded together
• Pure substance


  consists of only one element/compound
• Formulation


  a mixture that has been designed as a useful product
• Distillation


  separation of substances due to a difference in their boiling point
• Chromatography


  a method of separation and analysis of a mixture of soluble chemical substances

  USED FOR:

  identifying additives in food

  identifying drugs and alcohol

  comparing fibres found at crime scenes

  detecting bombs in airports

  fingerprinting
• Retention Factor (Rf)


  Rf = Distance moved by substance / Distance moved by solvent
• Isotopes


  atoms of the same element, with the same number of protons but a different number of neutrons
• Relative Atomic Mass (Ar)


  Ar = total mass of all atoms / total number of atoms
• PROTONS / NEUTRONS / ELECTRONS + MASS / ATOMIC NUMBER

  P = atomic number

  N = mass number - atomic number

  E = atomic number

  Mass number = top left of element

  Atomic number = bottom left of element
• Atoms are more stable with a full outer shell.

  They lose/gain electrons to achieve this.

  The further electrons are from the nucleus, the less stable the element is.

  
  

  Outer shell electron is further away from the nucleus. Therefore, there is less attraction between the nucleus and the outer shell electrons. The outer shell electron is more easily lost.
• Metal and non-metal elements typically form ionic bonds
• Positive Ions


  Lithium = Li⁺ (Flame Test = red/crimson)

  Sodium = Na⁺ (Flame Test = yellow)

  Potassium = K⁺ (Flame Test = lilac/purple)

  Copper = Cu²⁺ (Flame Test = green) (sodium hydroxide = blue precipitate)

  Calcium = Ca²⁺ (Flame Test = red/orange) (sodium hydroxide = white precipitate [doesn't dissolve in excess])

  Magnesium = Mg²⁺ (sodium hydroxide = white precipitate [doesn't dissolve in excess])

  Aluminium = Al³⁺ (sodium hydroxide = white precipitate [does dissolve in excess])

  Iron (II) = Fe²⁺ (sodium hydroxide = green precipitate)

  Iron (III) = Fe³⁺ (sodium hydroxide = brown precipitate)
• Negative Ions


  Carbonate = CO₃²⁻ (carbonate = bubbles of gas [limewater cloudy])

  Sulfate = SO₄²⁻ (sulfate = white precipitate)

  Chloride = Cl⁻ (halide = white precipitate)

  Bromide = Br⁻ (halide = cream precipitate)

  Iodide = I⁻ (halide = yellow precipitate)
• Identifying gases


  Oxygen = O₂ = insert a glowing splint into gas = splint relights

  Hydrogen = H₂ = inset a burning splint into gas = squeaky pop sound

  Carbon dioxide = CO₂ = shake gas with limewater = limewater goes cloudy

  Chlorine = Cl₂ = insert litmus paper into gas = litmus paper is bleached (loses colour/turns white)
• Compound ions


  Hydroxide = OH⁻

  Nitrate = NO₃⁻

  Sulphate = SO₄²⁻

  Carbonate = CO₃²⁻

  Phosphate = PO₄³⁻

  Ammonium = NH₄⁺

  Oxide = O²⁻

  Sulfide = S²⁻
• Metal ions


  Silver = Ag⁺

  Copper = Cu²⁺

  Iron = Fe²⁺/Fe³⁺

  Zinc = Zn²⁺
• Diatomic


  two atoms covalently bonded in a molecule
• Group 0 - The Noble Gases

  Unreactive

  Don't form bonds easily

  Monatomic (exist as a singular atom)

  Density and boiling point increase going down the group

  Reactivity decreases going down the group

  Extremely stable as they have full outer shells

  Helium - He

  Neon - Ne

  Argon - Ar

  Krypton - Kr

  Xenon - Xe

  Radon - Rn

  Oganesson - Og
• Group 1 - The Alkali Metals


  Very reactive

  Must be stored under oil to keep air and water away from them

  Melting point increase going up the group

  Very soft

  Low densities

  Low melting points

  Reactivity increases going down the group

  Lithium - Li

  Sodium - Na

  Potassium - K

  Rubidium - Rb

  Caesium - Cs

  Francium - Fr
• Group 7 - The Halogens


  Non-metals

  Les reactive as you go down the group

  Brittle as solids

  Low density

  Dull

  Thermal and electrical insulators

  
  

  Fluorine - F (pale yellow gas at room temperature)

  Chlorine - Cl (pale green gas at room temperature)

  Bromine - Br (dark brown liquid at room temperature)

  Iodine - I (grey solid at room temperature)

  Astatine - At

  Tennessine - Ts
• Displacement


  a more reactive halogen can replace a less reactive halogen from a halide compound
• Transition Metals


  Central block in the Periodic Table - NOT A GROUP

  Form coloured compounds
• Rate of Reaction


  Rate of reaction = Product formed / time
• Collision Theory


  for a reaction to happen, the reactant particles must collide with energy greater than or equal to the activation energy
• Activation energy


  the minimum energy a particle needs to react
• Factors affecting Rate of Reaction: Concentration of solution

  increasing the concentration causes the rate to increase

  • there are more particles per unit volume
  • therefore, the frequency of successful collisions has increased
• Factors affecting Rate of Reaction: Surface Area of Solids

  increasing the SA causes the rate to decrease

  • there is less SA
  • there are less particles exposed for collision
  • therefore, the frequency of successful collision has decreased
• Factors affecting Rate of Reaction: Temperature


  increasing the temperature causes the rate to increase

  • the particles have more energy and move faster
  • therefore, the frequency of successful collisions has increased
  • and many more particles have energy greater than or equal to the activation energy
• Factors affecting Rate of Reaction: Pressure of Gases

  increasing the pressure of gases causes the rate to increase

  • less space between particles means more frequent successful collisions
• Factors affecting Rate of Reaction: Presence of a Catalyst


  the presence of a catalyst increases the rate of reaction

  • the catalyst provides an alternate route with lower activation energy
• Catalyst


  a substance that speed up a reaction (by providing an alternate route with lower activation energy) without using itself up
• Crude Oil


  a mixture of mainly hydrocarbons

  • the remains of sea plants and animals that dies and fell to the sea bed
  • pressure and high temperature caused oil to form over millions of years
  • crude oil is obtained by drilling
  • crude oil is mainly made up of a family of compound called alkanes
• Homologous Series


  a family of compounds with:

  • the same general formula
  • the same functional group
  • similar chemical properties
  • trend in physical properties
• Alkanes

  • carbon can make 4 bonds
  • hydrocarbons contain only hydrogen and carbon
  • alkanes are saturated (only have single covalent bonds

  General formula: CnH2n+2
• Fractional Distillation

  • mixture of hydrocarbons in crude oil are separated in fractional distillation by boiling point
  • fractions with the higher boiling point are extracted at the bottom of the fractionating column

  1. Crude oil is vapourised
  2. The hydrocarbon gases enter the column
  3. The hydrocarbon gases rise up the column
  4. As hydrocarbon gases rise up the column they cool down
  5. When the different hydrocarbons reach their boiling point in the column they condense
  6. The hydrocarbon fraction is collected
• Small alkanes


  Low boiling points

  Less intermolecular forces, less energy to overcome

  Runny

  Easy to ignite

  Burns with clean flame