C1 - PARTICLES

• what are the 3 states of matter?

  solid, liquid and gas
• what happens at the melting point?

  melting and freezing
• what happens at the boiling point?

  boiling and condensing
• when can evaporation occur?

  occurs at any temperature.
• a soild has:

  • the particles are arranged in a regular arrangement
  • the particles vibrate about a fixed position
  • the particles are very close
• a liquid has:

  • the particles are arranged in a random arrangement
  • the particles move around each other
  • the particles are close
• a gas has:

  • the particles are arranged in a random arrangement
  • the particles move quickly in all directions
  • the particles are far apart.
• what is a physical change?

  a change that doesnt involve a change in the identity of the substance.
• what is a chemical change?

  a change in which 1 or more substances are converted into different substances.
• reactant + reactant --> product
• why are physical changes easy to reverse?

  no new substance is formed during interconversions of state
• melting

  solid to liquid
• boiling

  liquid to gas
• freezing

  liquid to solid
• evaporation

  liquid to gas
• condensation

  gas to liquid
• sublimation

  solid to gas
• the stronger the forces between the particles, the higher the energy needed for melting and boiling to occur.
• limitations of particle theory

  • considers all particles to be small, solid and inelastic
  • doesnt consider the different particles, such as atoms, ions, molecules or mixtures of all 3
  • fails to consider the intermolecular forces between particles
• what was john Dalton atomic theory?

  atoms are tiny particles that cannot be created, destroyed or divided.

  atoms of the same element are identical.

  different atoms combine together to form new substances.
• what did JJ Thomson discover?

  electrons
• what experiment did thomson do? and what did it prove?

  the cathode ray experiment identified the electron as a negative subatomic particles, hence proving that atoms are divisible.
• what was thomsons model of the atom?

  Plum pudding model.
• what experiment did rutherford do?

  he shot a beam of alpha particles at a thin sheet of gold foil.
• what were rutherfords observations?

  • most passed through
  • some particles scattered but passed through
  • a few deflected back
• what was Bohr's model?

  he proposed that electrons orbit the nucleus in fixed shells or orbitals located at set distances from the nucleus.
• what is the radius of an atom?

  1x10^-10m
• the atomic number is the number of protons in the nucleus of an atom. it is equal to the number of electrons in the atom. no 2 elements have the same number of protons as the atomic number determines the position of the element on the periodic table.
• electrons can be lost, gained or shared during chemical processes, but the proton number does not change.
• the mass number is the total of protons and neutrons.
• isotopes are atoms of the same element that contains the same number of protons/electrons but a different number of neutrons.
• an ion is an atom that has a charge.
• what is a cation?

  a positive ion
• what is an anion?

  a negative ion