chemistry paper 1

• 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 add numbers in front of elements/compounds to balance
• Mixture


  Any combination of different types of elements and compounds that are chemically bonded together
• Mixtures


  • Air
  • Salt water
• Solution


  Mixture of a solute dissolved in a solvent
• Separating mixtures


  1. Filtration

  2. Crystallization

  3. Distillation
• Obtaining pure substances is important in chemistry
• Purity


  Determined by testing the melting point or boiling point - a pure substance has a very specific temperature
• Formulation


  Mixture that has been specially designed to be useful in a very specific way
• Formulations


  • Paints
  • Fuels
  • Alloys
  • Fertilizers
• Chromatography


  Technique for separating substances in a mixture
• Chromatography


  1. Stationary phase (e.g. paper)

  2. Mobile phase (e.g. water) rises up paper by capillary action

  3. Measure distance moved by substances and calculate RF value
• States of matter


  • Solid
  • Liquid
  • Gas
• States of matter


  • Solids have fixed positions, liquids can move past each other, gases have particles far apart and move randomly
  • Gases can be compressed, solids and liquids cannot
• Changing state


  Melt or evaporate by supplying energy, usually heat, to overcome electrostatic forces
• Physical changes do not create new substances, only change state
• State symbols


  s for solid, l for liquid, g for gas, aq for aqueous (dissolved)
• Atom


  Positive charge with negative electrons orbiting, mostly empty space
• Atom models


  • Plum pudding model (Thomson)
  • Nuclear model (Rutherford)
  • Electron shells/orbitals (Bohr)
• Proton


  Positive charge in nucleus
• Neutron


  Neutral charge in nucleus
• Electron


  Negative charge orbiting nucleus
• Atomic number


  Number of protons in nucleus
• Mass number


  Number of protons and neutrons in nucleus
• Isotopes


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


  Percentage of each isotope in a sample
• Periodic table


  Organises elements by properties, not just atomic weight
• Electron configuration


  Arrangement of electrons in shells around nucleus
• Periodic table sections


  • Metals (left of staircase)
  • Nonmetals (right of staircase)
• Group


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


  Group 1, donate 1 electron
• Halogens


  Group 7, need 1 electron to fill outer shell
• Noble gases


  Group 0, very unreactive