Chemistry paper 1

• Substances are made of atoms
• Compound


  A substance that contains two or more different types of atoms chemically bonded together
• Chemical reaction

  Atoms change what they're bonded to and how they're bonded
• Chemical equation


  A representation of a chemical reaction using symbols
• Atoms are not created or destroyed in any chemical reaction, so the same number of each type of atom must be on both sides of the equation
• Mixture

  Any combination of different types of elements and compounds that aren't chemically bonded together
• Solution

  A mixture of a solute (dissolved substance) and a solvent
• Filtration

  Separating large insoluble particles from a liquid
• Crystallization

  Leaving a solute (solid dissolved in a liquid) behind after evaporating the solvent
• Distillation

  Heating a solution and condensing the gas to separate different liquids based on their boiling points
• Filtration, crystallization, and distillation are physical processes, not chemical reactions
• States of matter

  Solid, liquid, gas
• Water can exist as a solid (ice), liquid, or gas (water vapor)
• Melting and evaporation

  Require energy (usually heat) to overcome the electrostatic forces of attraction between particles, but do not create new substances (physical changes)
• Atom

  • Consists of a positive nucleus with negative electrons orbiting it
• Plum pudding model of the atom

  • Proposed by J.J. Thomson, with a positive charge and electrons dotted around it
• Rutherford's model of the atom


  • Discovered the positive charge is concentrated in a tiny nucleus, with electrons orbiting relatively far away
• Bohr's model of the atom


  • Electrons exist in discrete shells or orbitals around the nucleus
• Atom

  • Protons and neutrons have a relative mass of 1, electrons have a very small mass
• Atomic number


  The number of protons in the nucleus of an atom
• Mass number

  The total number of protons and neutrons in the nucleus of an atom
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Relative abundance


  The percentage of each isotope of an element found naturally
• The periodic table was originally ordered by atomic weight, then later by atomic number and properties
• Sections of the periodic table

  • Metals (left of staircase)
  • Non-metals (right of staircase)
• Group


  The column an atom is in on the periodic table, indicating the number of electrons in its outer shell
• Group 1 (alkali metals)


  • Have one electron in their outer shell which they readily donate
  • Reactivity increases down the group
• Group 7 (halogens)


  • Have seven electrons in their outer shell, needing one more to be full
  • Reactivity decreases down the group
• Group 0 (noble gases)


  • Have a full outer shell of electrons, so are very unreactive
• Ion


  An atom that has gained or lost one or more electrons, giving it an overall positive or negative charge
• Transition metals


  • Can form ions with different charges depending on how many electrons they donate
• Metallic bonding


  Bonding in metals, with a lattice of positive ions and delocalized electrons
• Ionic bonding


  Bonding between a metal and a non-metal, where the metal donates electrons to the non-metal
• Covalent bonding


  Bonding between non-metals, where they share electrons to fill their outer shells
• Molecular ion


  An ion formed from a group of atoms, e.g. hydroxide (OH-)
• Salt


  Any ionic compound, not just sodium chloride
• Simple molecular/covalent structures


  Individual molecules that can mix together, with relatively low boiling points
• Giant covalent structures


  Continuous networks of atoms bonded together, like diamond and graphite, with high melting/boiling points
• Allotropes


  Different structural forms of the same element, like diamond and graphite
• Nanoparticles


  Structures between 100-2500 nm in size, with a high surface area to volume ratio