chemistry paper 1

Cards (77)

  • Solids have a very fixed structure, atoms may wiggle a little but around a fixed point. Liquids have much more movement around but not in a fixed position, they can flow but not be compressed. Gases are very free to move, not in a fixed position, they can flow and be compressed.
  • Phase changes
    1. Melting: solid to liquid
    2. Evaporating: liquid to gas
    3. Condensing: gas to liquid
    4. Freezing: liquid to solid
  • Melting point
    Temperature at which a solid turns into a liquid
  • Boiling point
    Temperature at which a liquid turns into a gas
  • State symbols
    s = solid, l = liquid, aq = aqueous, g = gas
  • Liquid and liquid/aqueous and aqueous going to solid
    Turns cloudy
  • Liquid and solid/liquid and gas
    Bubbles or fizzing, loss of mass
  • Ionic compounds
    • Giant ionic lattice structure
    • High melting and boiling points
    • Only conduct when molten or dissolved
  • Simple covalent compounds
    • Small molecular structures
    • Low melting and boiling points
    • Generally gases or liquids at room temp
    • Do not conduct electricity
  • Giant covalent compounds

    • Giant covalent structure
    • High melting and boiling points
    • Do not conduct or dissolve
  • Metals
    • Positive atoms in a sea of delocalised electrons
    • Able to conduct electricity and heat
  • Alloys
    • Positive ions and delocalised electrons, plus other elements added
    • Distorted layers, cannot slide, so are hard
  • Polymers with crosslinks
    • Very fixed in place, burn upon heating
  • Polymers without crosslinks
    • Can slide across each other, melt upon heating
  • Mole
    Unit for amount of a substance, 6.02 x 10^23 atoms/ions/molecules
  • Reactivity series of metals
    • Most reactive at top, least reactive at bottom
    • Metals above carbon need electrolysis to extract
    • Metals below carbon can be extracted by reduction
    • Unreactive metals like Au, Ag, Cu found as pure ores
  • Oxidation
    Loss of electrons
  • Reduction
    Gain of electrons
  • Balancing half-equations for electrolysis
    1. Balance elements
    2. Balance charges by adding electrons
  • Reactions of acids
    • Acid + metal -> salt + hydrogen
    • Acid + metal oxide -> salt + water
    • Acid + metal hydroxide -> salt + water
    • Acid + metal carbonate -> salt + water + carbon dioxide
  • Neutralization
    Hydrogen ions + hydroxide ions -> water
  • Titration
    1. Add alkali to conical flask
    2. Add indicator
    3. Fill burette with acid of known concentration
    4. Slowly add acid, recording volume until colour change
    5. Repeat to get accurate result
  • Strong vs weak acids
    Strong acids fully dissociate, weak acids partially dissociate
  • Strong acids are: hydrochloric, nitric, sulfuric, hydrobromic, hydroiodic, chloric
  • Ionic compounds must be molten or dissolved to conduct electricity
  • Strong acid
    Hydroxide ions and hydrogen ions are fully dissociated, not touching each other, at high concentration
  • Strong acid
    Hydroxide ions and hydrogen ions are fully dissociated, but at low concentration there aren't many ions compared to water molecules
  • Weak acid
    Partially dissociated, some hydrogen and hydroxide ions are separated, some are still together
  • Weak acid at high concentration
    Lots of acid particles, very few water particles
  • Weak acid at low concentration
    Not many acid molecules per water molecule
  • Ionic compounds
    Must be molten or dissolved to conduct electricity, as ions are free to move around
  • Aluminium electrolysis
    1. Positive aluminium ions attracted to negative cathode, pick up electrons to form aluminium atoms
    2. Negative oxygen ions attracted to positive carbon anode, lose electrons to form oxygen gas
    3. Carbon electrode reacts with oxygen gas, forming carbon dioxide and wearing away the electrode
  • Endothermic reaction

    Takes in energy, feels colder
  • Exothermic reaction

    Gives out energy, feels hotter
  • Endothermic reactions have higher energy products than reactants, exothermic reactions have lower energy products than reactants
  • Endothermic and exothermic reactions
    • Endothermic: Electrolysis
    Exothermic: Burning, Neutralization
  • Calculating energy change of a reaction
    1. Write balanced equation
    2. List bonds broken and formed, multiply by bond energies
    3. Subtract energy of reactants from energy of products to get overall energy change
  • Exothermic reaction
    Has a negative energy change, meaning energy is released
  • Making copper sulfate
    1. Heat sulfuric acid, stir in copper oxide until in excess
    2. Filter to remove excess copper oxide
    3. Evaporate solution to leave copper sulfate crystals
  • Common electrolysis setups
    • Sodium chloride
    • Sodium sulfate
    • Copper chloride
    • Copper sulfate