Chem Topic 1

• What is an element?


  A substance containing only one type of atom.
• What is a compound?


  A compound is a substance composed of two or more elements chemically bonded together.
• How does conservation of mass link to equations?

  It states that atoms neither can be created or destroyed in a reaction thus meaning an equation must be balanced.
• What is a mixture?

  A combination of two or more substances that are not chemically bonded.
• What are the different separation techniques?

  • Filtration removes large insoluble particles from a liquid (e.g sand from water).
  • Evaporation leaves behind crystals of a solute if heated gently.
  • Lab distillation involves condensing the evaporated solvent and collecting it.
  • Chromatography causes substances to rise up paper due to capillary action. Lighter particles move up faster.
• What are the 3 states of matter?

  Solid, liquid, gas
• What do liquid and solids have in common?

  They cannot be compressed unlike gases.
• How are particles arranged in solids?

  Particles are in a lattice and vibrate about a fixed point.
• How are particles arranged in liquids?

  Particles have no regular arrangement and are able to move past each other.
• How are particles arranged in gases?

  Particles are far apart and randomly move at high speeds.
• What are the 6 changes of matter?

  1. Melting - changing from solid to liquid.
  2. Freezing - changing from a liquid to a solid.
  3. Vapourisation - changing from liquid to gas.
  4. Condensation - changing from gas to a liquid.
  5. Deposition - changing from gas to a solid.
  6. Sublimation - changing from a solid to gas.
• Energy is needed to overcome what?

  Forces of attraction between particles to melt/evaporate.
• Who contributed to the history of the atom? (In order)

  Democritus, Dalton, Thomson, Rutherford, Bohr, Chadwick
• What was democritus theory for the atom?

  Atomic theory, everything is made from tiny particles seperated by empty space.
• What was John Dalton's contribution to the history of the atom?

  He believed that atoms were solid spheres and different spheres made up elements
• What was JJ Thomson's contribution to the history of the atom?

  Discovery of the electron as well as the plum pudding model which was a sphere with a positive charge with electrons embedded within it.
• What was Rutherford's contribution to the history of the atom?

  Nuclear model. He discovered that the nucleus was small and positively charged by finding that alpha particles went straight though a thin sheet of gold and very few reflected back.
• What was Bohr's contribution to the history of the atom?

  He deduced that electrons existed in shells.
• What was Chadwick's contribution to the history of the atom?

  He determined that the nucleus must contain neutrons as well as protons.
• What is the model of the current atom like?

  • In the middle was the nucleus which contained neutrons and protons.
  • Electrons orbit around the shell.
• What is the relative charge of a proton, neutron and electron?

  Proton: +1 Neutron: 0 Electron: -1
• What is the relative mass of a proton, neutron and electron?

  Proton: 1 Neutron: 1 Electron: 0.0005 or (very small)
• What is the order of discovery of subatomic particles?

  Electron, proton, neutron
• What is the mass number?

  The total number of protons and neutrons in an atom's nucleus as well as the number at the top of an element.
• What is an atomic number?

  Number of protons in a nucleus, the bottom number.
• What is an isotope?

  An isotope is an element with different number of electrons.
• How do you calculate relative abundance?

  Total mass of 100 atoms/ 100
• How was the periodic table originally ordered?

  By atomic mass and some being grouped for having similar properties.
• What did Dmitri Mendeleev show?


  He showed that it made more sense to swap/reverse some elements.
• What did Dmitri's table have?

  It had gaps in that he predicted for undiscovered elements and in time the table was proven largely correct and served as the base for the modern periodic table.
• What is the order in which electrons can fill shells?

  2,8,8,2 (anything past calcium are transition metals)
• Where are metals located in the periodic table and what are their properties?

  Metals are located on the left side of the periodic table. They donate electrons to gain an empty outer shell to form positive ions.
• Where are non-metals located and what are their properties?

  Right side of the periodic table and always accept electrons to gain a full outer shell. They can form negative ions as well.
• What is a group?

  Number of electrons in outer shell
• What are alkali metals?


  Group 1 elements. They are all + ions and as get more reactive down the group as outer electron is further from nucleus so force of attraction is less.
• What are halogens?


  Group 7 elements that form - ions. They get less reactive as you go down but boiling point increases.
• What are noble gases?

  Group 0 elements and are very unreactive due to their empty outer shell.
• What are transition metals?


  Can donate different number of electrons.