Science exam review

• Physical change - same substance with altered physical properties

  ex. ice cube melting
• Chemical change - a new substance is formed

  ex. baking
• physical property - describes a substance

  ex. height, shape, colour
• chemical property - when a material's properties become evident during or after a chemical reaction

  ex. flammability
• Atom - basic unit of a chemical element
• molecule - 2+ atoms combined
• element - made up of 1 type of atom
• compound - made of the same type of molecule
• pure substance - made up of 1 type of particle
• mixture - 2+ types of particles
• alloy - a solid solution of 2+ metals

  ex. sodder (tin and lead)
• homogenous - same throughout

  ex. apple juice
• heterogenous - different throughout

  ex. pizza
• mechanical mixture - able to see the physical components

  ex. granola bar
• solution - homogenous mixture

  ex. air
• colloid - homogenous, opaque, mixture

  ex. milk
• suspension - particles are too large to be mixed so they fall out

  ex. paint, yogurt
• atomic mass- the mass of an atom

  proton - 1amu

  neutron - 1amu

  electron 0amu
• atomic number- number of protons an atom has
• isotope - heavier atom (same protons, more neutrons)
• ion - atoms with a charge

  cation - positive (loses electrons)

  anion - negative (gains electrons)
• proton - positively charged particle
• neutron - no charge
• electron - negatively charged particle
• valence shell - outermost shell of any atom
• valence electrons - electrons in the valence shell
• polyatomic ion - ion that contains more than one atom
• multivalent ion - ion with more than one charge

  ex. copper (+1 and +2)
• atomic radius- the distance between the nucleus and the outermost electron shell in an atom
• hydrogen - flaming - makes pop sound
• oxygen - glowing - re-ignites
• carbon dioxide - flaming - extinguishes
• location of proton and neutron - nucleus of atom

  location of electron - surrounding the nucleus
• Plum pudding - (J J Thomson) - represents negative electrons in a positive framework
• Nuclear model (Ernest Rutherford) - represents the atom as mostly empty space, with a tiny dense positively charged nucleus
• Solar system model (Niels Bohr) - represents electrons orbiting around the nucleus of the atom
• Gold Experiment - (Ernest Rutherford) - He shot a beam of alpha particles, which were positive at a sheet of gold foil and some of the particles deflected. Because of this, he concluded that the atom was made up of mostly empty space surrounding a tiny, dense nucleus. Problem: Couldn't explain why the negative electrons didn't fall into the positive nucleus.
• Bohr modified the Rutherford model by requiring that the electrons move in orbits of fixed size and energy.
• Period - Horizontal rows on periodic table 1-7
• Groups - Noble gases, halogens, other non metals, other metals, transition metals, rare earth and lanthanoid elements, alkaline earth metals, alkali metals, acinoid elements