chem paper 1

• Element: a substance containing only one type of atom.
• Compound: a substance containing two or more different types of atoms chemically bound.
• Mixture: different substances not chemically bound.
• what does filtration do?

  removes large, insoluble particles from a liquid e.g sand from water.
• what does EVAPORATION do?

  leaves behind crystals of a dissolved substance(solute) if heated gently.
• What is DISTILATION?

  involves condensing the evaporated solvent and collecting it.
• What is FRACTIONAL DISTILATION?

  separates liquids due to their different boiling points.
• what did the ancient greeks think about the atom?

  believed it was invisible particles.
• What did JJ Thomson do?

  -Discovered the electron.

  -created the plum pudding model.
• What did Ernest Rutherford discover?

  -nucleus was small.

  -nucleus was positively charged through an experiment.
• What did Neils Bohr discover?

  -electrons orbit the nucleus in shells.
• What did James chadwick do?

  -discover neutrons
• Who discovered protons?

  -Ernest rutherford
• mass number?

  number of PROTONS + NEUTRONS in a nucleus
• Atomic number?

  The number of protons in an atom's nucleus.
• What is an isotope?

  -same element JUST different number of protons.
• who made the first periodic table?

  Dmitri Mendeleev
• do metals form positive ions?

  yes as they DONATE electrons to gain an EMPTY OUTER shell.
• what is the name and properties of group 1 metals

  name- alkali

  properties- soft, reactive metals increasing as you go down the group with low boiling points.
• what are the properties and name of group 7?

  name- halogens

  properties- less reactive down the group and boiling point increases.
• what is the name and properties of group 0/8

  name- noble gases

  properties- very un reactive colourless, odourless and tasteless.
• what is metallic bonding?

  the electrostatic attraction between metal cations and delocalized electrons.
• what are metals good at?

  conducting heat and electricity as the electrons are free to move
• how do metals bond to non metals?

  ionic bonding-which is metal atoms donating electrons to non metals to form IONS.
• what is an ionic crystal?

  ions arranged in a lattice (grid) of repeating units of positive and negative IONS
• qualities of ionic substances?

  -HIGH MELTING/BOILING POINTS

  why?

  STRONG IONIC BONDS (as the ions have strong electrostatic forces between them)
• when can ionic compounds conduct electricity?

  when molten (liquified by heat) or in solution (dissolved) this is because the ions are free to move in these states. And they carry charge.
• what is covalent bonding?

  how non metals bond to each other by SHARING electrons to gain FULL OUTER SHELLS.
• what do covalent bonds consist of?

  a PAIR OF SHARED ELECTRONS.
• what are SIMPLE COVALENT STRUCTURES?

  molecules with a small number of atoms which have low boiling points due to weak intermolecular forces
• what is an allotrope?

  Different forms of the same element.
• what is a molecule?

  particle consisting of two or more atoms chemically bonded together.
• what is a giant covalent bond?

  a substance containing a large number of atoms covalently bonded.
• what is an alloy and what does it do?

  alloys are metals that contain atoms that are different shapes which disrupts the lattice so layers cannot slide over eachover.
• why is diamond one if the hardest substances?

  very strong bonds
• why does graphite have weak layers?

  delocalised electrons form weak bonds
• why can graphite conduct electricity?

  because the electrons can move.
• what is graphene?

  A single layer of carbon atoms arranged in a hexagonal lattice.
• what are moles used for?

  used to compare quantities of substances 12g carbon = 1 mole
• how do you calculate moles?

  moles= grams divided by ‘rams’

  moles= mass (g) divided by relative atomic/formula mass