Revision of elements

• Atom

  The smallest known particle present in all forms of matter. It retains the elements' identity.
• Proton

  A positively charged subatomic particle within an atom, found in the nucleus
• Neutron

  A neutrally charged subatomic particle within an atom, found in the nucleus
• Electron

  A negatively charged subatomic particle within an atom, found in the electron shell.
• Electron Configuration

  First shell: 2 electrons

  Second shell: 8 electrons

  Third shell: 18 electrons

  Fourth shell: 32 electrons

  Fifth shell: 50 electrons

  Sixth: 72 electrons

  Seventh: 98 electrons
• Relative mass of protons, neutrons and electrons

  Protons have a mass of approximately 1 amu (atomic mass unit), and neutrons have a mass of approximately 1.008 amu, however electrons have basically no mass. This means that the atom's mass will come from the nucleus.
• Atomic Number vs Atomic Mass

  The atomic number of an element tells you how many protons (and therefore electrons) there are in the atom, whereas the atomic mass tells you the total mass of the atom (which can be used with the atomic number to calculate how many neutrons are in the atom).
• Chemical Reaction

  A chemical reaction is when two or more elements or compounds combine, rearranging their atoms to form new substances.
• Reactant

  Reactants are the substances at the start of the chemical reaction that combine and rearrange to form new substances. They are on the left-hand side of the chemical equation.
• Product

  Products are substances formed in a chemical reaction by the reactants. It is on the right-hand side of the chemical equation.
• Elements vs COmpounds

  Elements are pure substances made up of only one type of atom and can't be broken down into other elements. e.g. Boron, Oxygen, Hydrogen. Compounds are substances chemically bonded with more than one type of atom in a fixed ratio and can be broken down into other elements. e.g. Methane, Water, Carbon Dioxide.
• The Law of Conservation of Mass

  The law of conservation of mass states that the total mass of reactants is equal to the total mass of products as atoms can't be produced or destroyed during a chemical reaction.
• Acids

  • Corrosive
  • Conducts electricity
  • Sour taste
  • Some produce Hydrogen gas and salt when it reacts with certain metals
  • All acids are neutralised by bases, producing water and salt
  • All acids release hydrogen ions (H+) into a solution
  • All acids should turn blue litmus paper red
  • e.g. Hydrochloric acid, Sulfuric acid, Nitric acid
• Bases

  • Caustic
  • Soapy and slimy texture
  • Bitter taste
  • Conducts electricity
  • All bases are neutralised by acids, producing water and salt
  • All bases release hydroxide ions into solutions (OH-)
  • All bases should turn red Litmus paper blue
  • e.g. Sodium hydroxide, ammonium hydroxide, potassium hydroxide
• pH scale


  pH is the measure of the strength of an acid or base/alkali. If a substance is an acid its pH will be less than 7. If a substance is basic its pH will be more than 7. If a substance is neutral its pH will be 7.
• pH testing using indicators


  To conduct a pH test using a universal indicator, put a couple of drops into the solution that needed to be tested. If the colour of the solution turns more green/yellow/orange/red, it's an acid. If the solution turns more pink/blue/purple it's a base. A strong acid is likely to make the solution go a distinct red colour. A strong base is likely to make the solution go a distinct blue/purple.
• Salts

  Salts are generally made of a metal and a non-metal when they react
• Acid-Bases reaction

  When acids and bases react, they neutralise and produce water and salt. This is also called a neutralisation reaction. To know if a substance in a chemical equation is a base, it will have OH/hydroxide in it.
• What product is always formed in acid reactions?

  Salts are always formed in acid reactions
• Predicting the name of salts

  If hydrochloric acid is reacted with something the salt will be a chloride. If nitric acid is used, the salt will be a nitrate. If sulfuric acid is used, the salt will be a sulfate.
• What type of reaction is: Hydrochloric acid + sodium hydroxide --> sodium chloride and water

  This is a neutralisation reaction between an acid and a base
• Neutralisation reaction


  Neutralisation occurs when an acid and a base come together and react, producing salt and water.

  • Formula: Acid + Base --> Salt + Water
• Acid-Metal reaction


  An acid-metal reaction occurs when an acid and metal react and produce Hydrogen gas (H2) and salt.

  • Formula: Acid + Metal --> Salt + Hydrogen gas
• Acid-Carbonate reaction

  An acid-carbonate reaction occurs when an acid and any form of carbonate or hydrogen carbonate react and produce salt, water and carbon dioxide

  • Formula: Acid + Carbonate --> Salt + Water + Carbon Dioxide
  • Formula: Acid + Hydrogen Carbonate --> Salt + Water + Carbon Dioxide
• Combustion reaction

  Combustion is when a compound is burnt in oxygen, reacting to produce carbon dioxide and water. In a combustion reaction, oxygen is always one of the reactants.
• Photosynthesis vs cellular respiration

  Cellular respiration is when cells in bodies use a combustion reaction to get their energy. In this process, oxygen and glucose react and produce carbon dioxide and water, releasing energy. In photosynthesis, plants also produce their own energy, though it is not through combustion. Carbon dioxide, water and light energy produce glucose and oxygen. The reaction occurs in the green parts of the plant filled with chlorophyll.
• Is respiration an endothermic or exothermic reaction?

  Respiration is an exothermic reaction as more energy (ATP) is released during the process than absorbed.
• Respiration formula

  Oxygen + Glucose --> Carbon Dioxide + Water
• What charge do atoms have?

  Atoms always have a neutral charge as they have the same number of protons as electrons
• What does the arrow in a chemical equation mean?

  The arrow means "yield" and shows the direction in which the reaction occurs
• What does the subscript represent in a chemical formula?

  The subscript represents how many of the atom there are
• In a chemical reaction, the properties of the product is different to that of the reactants that made it.
• Methane = CH4
• When you want to balance an equation you can only change the coefficient of an element/compound, but can't change the subscript
• If the acid or base dissociates completely in a solution, it's classified as strong. If it partially dissociates in a solution, it is classified as weak
• Strong acids

  • Hydrochloric acid
  • Sulfuric acid
  • Nitric acid
  • Battery acid
  • Stomach acid
  • Lemon juice
• Weak acids

  Acetic acid

  Carbonic acid

  Phosphoric acid

  Wine

  Bananas

  Black coffee

  Milk
• Strong bases

  • Sodium hydroxide
  • Potassium hydroxide
  • Barium hydroxide
  • Hair remover
  • Oven cleaner
  • Drain remover
• Weak Bases

  Ammonium

  Household bleach

  Blood

  Egg whites

  Baking soda
• Ionic Compounds

  Compounds formed between metal and non-metal elements. When naming the non-metal element the suffix "ide" is used after the stem of the name. e.g. Sulfur becomes sulfide.