chem paper 1 🧪👩🏿‍🔬

• Conservation of Mass states atoms can’t be created or destroyed. Therefore, chemical equations must be balanced.
• Filtration - The process of separating a liquid from a solid by passing it through a filter.
• Evaporation - The process of water evaporating from a liquid to a gas, leaving crystals of a dissolved solute behind.
• Distillation - Separates a liquid from a solution by evaporating the liquid and condensing the vapour and collecting it.
• Fractional distillation separates liquids due to their different boiling points.
• Chromatography - Causes substances to rise up the paper due to capillary action. The lighter particles move further up.
• An isotope is an element that is the same but has a different number of neutrons.
• The average mass of an isotope is :

  Total mass of 100 atoms

  ——————————————

  100
• Metals always donate an electron to gain an empty outer shell. This forms a positive ion.
• Non metals receive an electron to gain a full outer shell. This forms negative ions.
• Hydrogen only has 1 electron so it can donate and receive electrons.
• Group 1 metals are known as alkali metals because they react with water to produce an alkali.
• Group 1 metals lose / donate their outer electrons so that they become POSITIVE ions. Eg Na+.
• Group 1 metals get more reactive as you go down the group because the electron is further from the nucleus.
• The further away electrons are from the nucleus, the lower the force of attraction is. This is because there is less electrostatic attraction between the electrons and the nucleus.
• Group 7 halogens have 7 electrons in their outer shell.
• Group 7 atoms form negative ions as they receive an electron to gain a full outer shell. Eg Cl-.
• Group 7 atoms get less reactive as you go down the group because they have more protons and electrons. Their boiling point also increases as you go down.
• Group 0 are known as noble gases.
• noble gases don’t react due to their empty outer shells.
• If a group 2 element gives away 2 electrons, it is shown as Be2+

  and vice versa .
• A delocalised electron is an electron that is not confined to a single atom or molecule.
• Metallic bonding is how metal atoms bond to each other.
• Metals bond metallically by forming a lattice of ions surrounded by a ’sea‘ of delocalised electrons.
• Why are metallically bonded metals good conductors?

  They have free-to-move electrons which allow heat and electricity to be conducted .
• Ionic bonding is how metals bond to non metals.
• In ionic bonding, metals donate their electrons to non metals in order for them to both have a full outer shell.
• A lattice is an ionic structure that consists of repeating units of positive and negative charges. This forms a crystal.
• Ionic structures have high melting and boiling points because of the strong ionic bonds due to the electrostatic forces between them.
• Ionic structures can conduct electricity when molten or dissolved in a solution because the ions are free to move and can therefore carry a charge.
• Magnesium Hydroxide ( Mg(OH)2 is a molecular ion as 2 OH are needed to bond with magnesium.
• Examples of Molecular ions are :

  • Sulphate ion : SO4 2-
  • Carbonate ion : CO3 2-
  • Nitrate ion : NO3-
  • Ammonium ion : NH4+
• Ionic bonds are known as salts.
• Covalent bonds are how non metals bond with eachother.
• In covalent bonding, electrons are shared in a Venn diagram like way.
• O2 is a double bond and therefore looks like this O=O.
• Simple covalent structures are small molecules which atoms are held together by covalent bonds.
• Simple covalent structures have low boiling points due to weak intermolecular forces.
• Simple covalent structures can’t conduct electricity.
• Diamond and Silicon Dioxide are examples of giant covalent structures.