Chemistry Paper 1 (Science)

• Substances are made of atoms
• Element


  Different types of atoms represented in the periodic table by a symbol
• Compound


  Substance that contains two or more different types of atoms chemically bonded together
• If there's no number after a symbol, there's an invisible 1
• Chemical reaction

  Atoms change what they're bonded to and how they're bonded
• Word equation

  Representation of a chemical reaction using words
• Chemical equation

  Representation of a chemical reaction using symbols
• Atoms are not created or destroyed in any chemical reaction, so the same number of each type of atom must be on both sides of the equation</b>
• Balancing a chemical equation

  Start with atoms only in compounds, then balance remaining atoms by putting numbers in front of elements/compounds
• Mixture


  Any combination of different types of elements and compounds that aren't chemically bonded together
• Solution


  Mixture of a solute (solid dissolved in a liquid) and a solvent
• Separation techniques


  1. Filtration (separate large insoluble particles from a liquid)

  2. Crystallization (evaporate solvent to leave behind solute)

  3. Distillation (separate liquids based on different boiling points)
• Physical processes

  • No new substances are being made, only separating existing mixtures
• States of matter


  • Solid (particles vibrate around fixed positions)
  • Liquid (particles can move past each other)
  • Gas (particles move randomly and have the most energy)
• Gases can be compressed, solids and liquids cannot
• Melting and evaporation


  Require energy (usually heat) to overcome electrostatic forces of attraction between particles
• Melting and evaporation are physical changes, not chemical reactions (no chemical bonds are broken)
• Atomic models


  • JJ Thompson's plum pudding model
  • Rutherford's discovery of the nucleus and mostly empty space
  • Bohr's discovery of electron shells/orbitals
  • Chadwick's discovery of neutrons
• Protons


  Positive charges in the nucleus
• Electrons


  Negative charges orbiting the nucleus
• Neutrons


  Neutral charges in the nucleus
• Atomic number


  Number of protons in the nucleus, determines the element
• Mass number


  Total number of protons and neutrons in the nucleus
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Relative abundance


  Percentage of each isotope in a sample of an element
• The periodic table was originally ordered by atomic weight, then later by atomic number and properties
• Electron configuration


  The arrangement of electrons in shells/orbitals around the nucleus
• Sections of the periodic table

  • Metals (left of staircase)
  • Non-metals (right of staircase)
  • Transition metals
• Group


  Column in the periodic table, indicates number of electrons in outer shell
• Alkali metals


  Group 1 elements, have 1 electron in outer shell which they readily donate
• Halogens

  Group 7 elements, have 7 electrons in outer shell and readily accept 1 more
• Noble gases


  Group 0 elements, have full outer shells and are very unreactive
• Positive ion


  Formed when a metal loses electrons
• Negative ion


  Formed when a non-metal gains electrons
• Metallic bonding


  Bonding in metals, with a lattice of positive ions and delocalized electrons
• Ionic bonding


  Bonding between a metal and a non-metal, where the metal donates electrons to the non-metal
• Covalent bonding


  Bonding between non-metals, where they share electrons to fill their outer shells
• Molecular ion


  An ion formed from a molecule, e.g. hydroxide ion (OH-)
• Salt


  Any ionic compound, not just sodium chloride
• Simple molecular/covalent structures


  Individual molecules that can mix together, have relatively low boiling points