Chem

• Molecule is two or more particles. All compounds are therefore molecules.
• Element

  A pure substance which contains atoms with the same number of protons and is found in the periodic table

  
• Compound

  A pure substance containing two or more different elements chemically bonded together
• Mixture

  Two or more different types of elements or compounds not chemically bonded together, typically easy to separate
• Electrons

  Are arranged around the nucleus in energy levels called shells

  
• Nucleons

  Protons and neutrons in the nucleus of the atom

  
• Atomic number

  The number of a chemical element in the periodic system, and the number of protons and electrons

  
• Atomic Mass

  Number of Nucleons
• Neutrons

  Atomic Mass - Atomic Number
• Isotopes

  Atoms of an element which have the same number of electrons and protons, but different amounts of neutrons, so they differ in mass and properties
• Ionic Bonding

  The electrostatic attraction between two oppositely charged ions, where one atom gains valence electrons from another (cation and anion)
• Covalent Bonding

  The electrostatic attraction between the shared electrons and the 2 nuclei that holds the atoms together in the molecules
• Charged particles

  • Cation: Positively charged ions, typically of metals
  • Anion: Negative charged ions, typically of non-metals
• Relative Atomic Mass

  The average of mass numbers in the different isotopes of an element, taking into account the relative abundance
• Differences between Ionic and Covalent Bonding

  • Ionic: High melting point, High boiling point, Soluble in Water, Stronger Bonds, Transferring electrons, Charged

  Covalent: Low melting point, Low boiling point, Insoluble in Water, Weaker Bonds, Sharing electrons, Neutral
• Testing for Carbon Dioxide

  1. Carbon dioxide gas passes through a tube into limewater

  2. The limewater reacts with the carbon dioxide gas to produce a precipitate of white calcium carbonate, which looks 'milky'
• Testing for Oxygen

  1. Insert a glowing splint into a tube of oxygen, it should reignite

  
• Testing for Hydrogen

  1. Insert a burning splint into a tube of hydrogen, you should hear a large squeaky pop sound

  2. Hydrogen burns to give water, and the pop sound is the result of the rapid combustion of hydrogen with oxygen to produce water

  
• Testing for Ammonia

  1. Ammonia gas will turn damp red litmus paper blue, because ammonia is an alkaline

  2. Hold the litmus paper near the mouth of the test tube, but be careful to avoid touch the sides of the test tube
• Testing for Water

  1. Put cobalt chloride paper in water

  2. The paper will turn from blue to pink/red, because cobalt chloride paper changes colour in response to humidity

  
• Testing for Chlorine

  1. Put blue litmus paper in chlorine gas

  2. The paper will turn from blue to red, as acids are produced when chlorine comes into contact with water, and then to white because the paper is bleached

  
• Testing for Iodine

  Iodine molecules combined with starch will make a blue black complex, compared to the original brown colour

  
• Signs of a chemical reaction

  • Colour Change
  • Effervescence (giving off a gas, bubbling)
  • Temperature Change
  • Precipitation (solid forms)
  • Dissolving Solid (if there is a solid reactant)
• Factors that affect a reaction

  • Temperature
  • Concentration
  • Surface Area
  • Catalysts
• Collision Theory


  In order for a reaction to occur, there must be a collision between reactant particles, and this collision must have sufficient energy (activation energy) and in the orientation or right place

  
• The chemical equation for the marble chips and HCL is: CaCO3 + HCl -> CaCl2 + CO2 + H2O
• As the time increases, so does the volume of gas produced. Towards the end of the reaction, the rate of reaction slows down because one reactant is used up, and this decreases the concentration of hydrochloric acid, which leads to less collision with the particles.
• The crushed tablets lost more cumulative mass compared to the whole tablets. A larger surface area leads to more mass loss because more particles are exposed to the other reactant. As the particles exposed to the reactants increase, there will be an increased frequency of collisions, therefore so did the rate of reaction.
• Mg + HCl -> MgCl2 + H2
• Magnesium + Hydrochloric Acid

  Magnesium Chloride + Hydrogen
• This is because the magnesium has more hydrochloric acid to react with, and since the reactant particles become more crowded, the frequency of collisions between reactant particles increases, therefore so does the rate of reaction
• Catalyst

  A substance which speeds up the rate of a reaction without itself being altered or consumed in the reaction
• Hydrogen Peroxide -> Water + oxygen
• 2H2O2 -> 2H2O + O2
• H2O + NaHCO3 → NaOH + H2CO3
• This is supported by collision theory, as an increase in temperature can speed up the reaction by increasing the percentage of collisions with sufficient activation energy and increasing the number of collisions

  
• Fuel

  A substance that we burn / react with oxygen (combustion) to get a useful amount of energy
• Examples of solid fuels

  • wood
  • charcoal
  • coal
• Examples of liquid fuels

  • Petroleum
  • diesel (artificial)
  • gasoline (artificial)
• Examples of gas fuels

  • Hydrogen
  • propane (C3H8)
  • methane (CH4)