(periodic table)

• a physical change is a change in physical properties of a substance without altering its chemical properties (e.g. state of matter)
• chemical change is the change of one or more substances into new ones with different chemical compositions and properties (e.g. sodium + chlorine = sodium chloride)
• noble gases (group 0) have a full outer shell, therefore unreactive to other elements
• noble gases have low boiling and melting points. The weak intermolecular force can be overcomed with small energy
• monoatomic is a molecule that consists of only one atom
• diatomic is a molecule that has two atoms
• polyatomic is a molecule that has more than two atoms
• properties of metals:

  • solid at room temperature
  • high melting points
  • strong and hard
  • dense
  • conductors
• properties of non-metals:

  • any state at room temperature
  • low melting points
  • soft
  • non-conductors
  • less dense than metals
• alkali metal + water = metal hydroxide + hydrogen
• alkali metals are very reactive to water, and are more reactive further down the group. They are soft and have relatively low melting points
• halogens (group 7) are less reactive further down the group, they will replace less reactive elements in displacement reactions
• chlorine (Cl):

  • colour + state at r.t.p = green gas
  • gas colour = green
  • solution colour = light green
• bromine (Br):

  • colour + state at r.t.p = brown liquid
  • gas colour = brown
  • solutiion colour = dark orange
• Iodine (I):

  • colour + state at r.t.p = dark grey solid
  • gas colour = purple
  • solution colour = dark red
• properties of metals:

  • solid at r.t.p
  • high melting/boiling points
  • dense
  • conductors
  • ductile + malleable
• metal oxides are basic (alkali), will show blue in universal indicator
• non-metal oxides are acidic, will show red in universal indicator
• alkali metals are stored in paraffin oil in glass jars to prevent moisture from reacting with it
• observations of lithium + water:

  • bubbles
  • floats
  • moves around
  • dissolves
• observations of sodium + water:

  • fizzing + bubbles
  • floats
  • melts into spherical shape (exothermic)
  • dissolves
• composition of air:

  nitrogen = 78%

  oxygen = 21%

  argon = 0.9%

  carbon dioxide = 0.04%
• ways to determine oxygen percentage in the air:

  • burning candle (burns, air pressure inside is less than outside, water rises)
  • iron wool (rusts, reacts with oxygen, air pressure causes water to rise)
• the temperature on earth depends on the amount of heat radiation it receives from the sun. If it emits the same as it receives, the temperature will stay constant
• carbon dioxide is a greenhouse gas in the atmosphere and traps heat, preventing the earth from freezing over
• infared radiation from the sun has a short wavelength so it can pass through the atmosphere. Raditation from earth has a longer wavelength
• greenhouse effect:

  • melting polar ice caps
  • extreme weather
  • rising sea levels
• fossial fuels produce carbon dioxide, and can be prevented by using renewable energy (solar, wind, hydrodam), education + advocacy, policies + regulations
• polyatomic ions:

  ammonium ion (NH4+)

  carbonate (CO3 2-)

  nitrate (NH3-)

  sulphate (SO4 2-)

  hydroxide (OH-)