chemistry

• the equation of neutralization is H+ + OH- = H2O
• solids have fixed mass, volume and shape. They have the lowest energy and are non-compressible.
• liquids have fixed mass and volume, not a fixed shape. energy is low in comparison to gas but more than solid. Are not compressible
• gases have no fixed mass or volume, they can take any shape. energy is high compared to solids and liquids. Are compressible.
• solids have a regular arrangement their particles are tightly packed together, close to each other, vibrate and have strong forces of attraction.
• liquids have an irregular arrangement their particles are close, slide across each other and the containers and they have weak forces of attraction between them.
• gases have an irregular arrangement of particles. Their particles are far apart, and move in all directions, continuously colliding with the walls and each other, random movement. they have no forces of attraction.
• Evaporation, only surface particles change into gas. It occurs in a range of 1-99 degree Celsius.
• Boiling, when temperature reaches boiling point, all liquid turns into gas. it occurs at 100 degrees celsius.
• sublimation: converting a solid to gas directly, without changing the solid to a liquid. Dry ice --> solid CO2 and NH4 salts and iodine.
• heating graph: starts from the lowest temperature 0.

  solid --> melting --> liquid --> boiling --> gas

  solid --> sublimation --> gas
• cooling graph: will start from the highest temperature.

  gas --> condensation --> liquid --> freezing --> solid

  gas --> sublimating --> solid
• effect of temperature:

  • if the temperature is increased volume is increased too.
  • kinetic energy of particles will increase so they move faster.
  • more collisions with the walls of the container per unit time. hence, exerting more pressure.
• effects of gas:

  • if pressure increases volume decreases
  • particles come closer, space between particles decreases.
• diffusion: indicates existence of particles. in this process particles move from an area of higher concentration to an area of lower concentration.
• rate of diffusion depends on the molecular mass (Mr) of the substance. The smaller the Mr the faster the rate of diffusion.
• molecular mass = sum of atomic masses of all atoms present in one molecule.
• Graham's law of diffusion - rate of diffusion is inversely proportional to the Mr
• mostly the mass of the atom is of the nucleus is a cluster of protons and neutrons, with electrons orbiting the nucleus. 2000 electrons = 1 proton.
• relative mass relative charge

  protons 1 +1

  neutrons 1 no charge

  electrons 1/1840 -1
• ion an uncharged particle - unequal number of protons and electrons
• isotope - atoms of the same element with same number of protons and electrons but different number of neutrons.
• arrangement of electron shells - 1st shell max 2e - 2nd shell max 8e - 3rd shell max 8e - 4th shell max 8e
• in noble gases valence shell is complete.
• group number is number of valence electrons in an element and period number can indicate the number of electron shells.
• relative mass is the average mass of atoms of an element compared to 1/12th of the mass of an atom of carbon 12.
• relative atomic mass can be calculated by first multiplying the isotophic mass with its percentage abundance of the two elements and then adding them and dividing them by 100.
• elements are arranged in ascending order in order of proton number.
• chemical properties in a group are similar as they are the same number of valence electrons.
• physical properties of metals:

  • good conductors
  • malleable and ductile
  • often shiny
• chemical properties of metals:

  • they have 1 -3 valence electrons
  • atoms can easily lose electrons and convert to + ion
  • can easily react with acids and oxygen
  • they form basic oxides
• physical properties of non-metals:

  • non-metals are poor conductors of heat and electricity
  • not shiny
• chemical properties of non-metals:

  • more than 3 electrons in the valence shell
  • atoms can easily gain electrons and convert to - ion
  • cannot react with acid or oxygen easily
  • form acidic oxides
• in the periodic table non-metal character increases left to right and metallic character decreases right to left.
• physical properties of alkali metals:

  • soft metals
  • low m.p & b.p
  • low density
  • silvery white solids
• chemical properties of alkali metals:

  • very reactive, reacts with oxygen to form metal oxide Na + O2 --> Na2O
  • reacts with water to form metal hydroxide and hydrogen Na + H2O --> NaOH + H2
  • can form ions with +1 charge only (fixed oxidation state/valency)
  • forms white compounds
  • does not act as catalyst
• physical properties of transition metals:

  • hard metals
  • high m.p
  • high density
  • grey solids or have their specific colors
• chemical properties of transition metals:

  • variable oxidation state
  • they form color compounds
  • act as catalyst
  • less reactive
  • react with oxygen to form oxides slow reaction Fe + O2 --> FeO
  • reacts with water slowly to form metal oxide and hydrogen at high temperature. Fe + H2O --> FeO + H2
• sodium sizzles and makes bubbles in water, floats, then turns molten and melts and disappears
• potassium bounces on the water surface reacts and creates a lilac flame