C2

    Cards (50)

    • States of matter
      Solid, liquid, gas
    • Melting and freezing
      Take place at the melting point
    • Boiling and condensing
      Take place at the boiling point
    • Energy needed to change state
      Depends on the strength of the forces between the particles
    • Particle theory model
      Particles represented by small solid spheres
    • Gas particles
      • Widely spaced, in constant quick motion, collisions are frequent and elastic, weak forces between particles
    • Liquid particles
      • Closely spaced, in constant motion, colliding, forces between particles less than in solid
    • Solid particles
      • Can only vibrate in a fixed position
    • Pure elements and compounds melt and boil at specific temperatures
    • Melting point and boiling point data can be used to distinguish pure substances from mixtures
    • Melting point curve

      Temperature stays horizontal when solid is melting as heat is absorbed to break bonds
    • Chemical equations
      States of matter shown as (s), (l) and (g), with (aq) for aqueous solutions
    • Ionic bonding
      Occurs in compounds formed from metals combined with non-metals
    • Electron transfer in ionic bonding
      Metal atoms lose electrons to become positively charged ions, non-metal atoms gain electrons to become negatively charged ions
    • Dot and cross diagram
      Represents electron transfer in ionic bonding
    • Ionic bond
      Electrostatic force of attraction between oppositely charged ions
    • Common charges of ions
      • Group 1 = +1, Group 2 = +2, Group 6 = -2, Group 7 = -1
    • Working out formulae for ionic compounds
      Combine ions so total positive charge equals total negative charge
    • Brackets in ionic formulae
      Used when there are two or more of a compound ion
    • Giant ionic structure
      Ionic compounds are a giant structure of ions held together by strong electrostatic forces of attraction
    • Properties of ionic substances
      • High melting and boiling points, do not conduct electricity when solid but do when molten or dissolved
    • Covalent bonding
      Occurs in non-metallic elements and compounds of non-metals, atoms share pairs of electrons
    • Covalent substances
      May consist of small molecules, have relatively low melting and boiling points, do not conduct electricity
    • Size of molecule
      Larger molecules have stronger intermolecular forces, higher melting and boiling points
    • Polymers
      Very large molecules, atoms linked by strong covalent bonds, intermolecular forces between polymer molecules are relatively weak
    • Small molecular covalent substances
      Substances that consist of small molecules, usually gases or liquids that have relatively low melting points and boiling points
    • Small molecular covalent substances
      • Have only weak intermolecular forces between the molecules
      • Intermolecular forces are overcome, not the covalent bonds, when the substance melts or boils
      • Require little energy to overcome intermolecular forces
      • Do not conduct electricity because the molecules do not have an overall electric charge
    • Molecular representation
      Molecules can be shown with sticks to represent covalent bonds or shown in a 3D way
    • Polymers
      • Very large molecules (not giant covalent structures)
      • Atoms in polymer molecules linked by strong covalent bonds
      • Intermolecular forces between polymer molecules are relatively strong, so they are solids at room temperature
      • Intermolecular forces are broken when a polymer melts
    • Polymer representation
      • C-C-H-H-H-H-n
    • Giant covalent substances
      • Solids with very high melting points
      • All atoms linked by strong covalent bonds
      • Bonds must be overcome to melt or boil
    • Giant covalent substances
      • Diamond
      • Graphite
      • Silicon dioxide (silica)
    • Diamond
      • Each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure
      • Very hard
      • Very high melting point
      • Does not conduct electricity
    • Graphite
      • Each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings
      • High melting point
      • Layers free to slide over each other, so graphite is soft and slippery
      • One electron from each carbon atom is delocalised, allowing graphite to conduct thermal energy and electricity
    • Graphene
      A single layer of graphite, one atom thick
    • Fullerenes
      • Molecules of carbon atoms with hollow shapes, based on hexagonal rings but may also contain five or seven carbon atom rings
      • First fullerene discovered was Buckminsterfullerene (C60) with a spherical shape
    • Carbon nanotubes
      • Cylindrical fullerenes with very high length to diameter ratios
      • Useful for nanotechnology, electronics and materials
    • Metallic bonding
      • Giant structures of atoms arranged in a regular pattern
      • Electrons in the outer shell of metal atoms are delocalised and free to move through the whole structure
      • Sharing of delocalised electrons gives rise to strong metallic bonds
    • Metallic bonding representation
      Delocalised electrons between positive ions
    • Properties of metals
      • Strong metallic bonding means high melting and boiling points
      • Good conductors of electricity due to delocalised electrons
      • Good conductors of thermal energy due to delocalised electrons