Chemistry

• Matter


  Any substance that has mass and occupies space
• States of matter


  • Solid
  • Liquid
  • Gas
• Solid


  • Strong forces of attraction between particles, particles are packed very closely together in a fixed and regular pattern
  • Atoms vibrate in position but can't change position or move
• Liquid


  • Weaker attractive forces than in solids, particles are close together in an irregular, unfixed pattern
  • Particles can move and slide past each other
• Gas


  • No intermolecular forces, particles are in random movement and so there is no defined pattern
  • Particles are far apart and move quickly (around 500 m/s) in all directions, they collide with each other and with the sides of the container
• Particle arrangement


  • Solid: Very closely packed, regularly arranged in lattice
  • Liquid: Closely packed, irregular arrangement
  • Gas: Very far apart, very irregular arrangement
• Solid


  • Fixed volume, almost no intermolecular spaces, extremely strong intermolecular forces, vibrating in a fixed position
• Liquid


  • Fixed volume, minimal intermolecular spaces, weaker intermolecular forces than solids, slowly slide over each other randomly
• Gas


  • Not fixed volume, very large intermolecular spaces, very weak intermolecular forces, fast movement in random direction
• Melting


  Solid changes into liquid, requires heat energy which transforms into kinetic energy, occurs at melting point
• Boiling


  Liquid changes into gas, requires heat which causes bubbles of gas to form, occurs at boiling point
• Freezing


  Liquid changes into solid, reverse of melting, occurs at same temperature as melting point
• Evaporation


  Liquid changes into gas, occurs at surface of liquid where high energy particles can escape, no heat required
• Condensation


  Gas changes into liquid, usually on cooling, particles lose energy and group together to form liquid
• When substances are heated, the particles absorb thermal energy which is converted into kinetic energy
• Heating a solid causes its particles to vibrate more until the structure breaks and the solid melts
• On further heating, the liquid substance now expands more and some particles at the surface gain sufficient energy to overcome the intermolecular forces and evaporate
• When the boiling point temperature is reached, all the particles gain enough energy to escape and the liquid boils
• Cooling down a gas has the reverse effect and this would be called a cooling curve
• Heating curves and cooling curves are used to show how changes in temperature affect changes of state
• Increase in temperature


  Increases the kinetic energy of gaseous particles, they move faster
• Decrease in temperature


  Decreases the kinetic energy of gaseous particles, they move slower
• Compressing a gas into a smaller space

  Increases the pressure
• Increasing temperature of a gas in a closed container

  Increases the pressure
• Diffusion


  The process by which different gases or different liquids mix due to the random motion of their particles
• Diffusion


  • Diffusing particles move from an area of high concentration to an area of low concentration, eventually the concentration becomes even
• Diffusion occurs faster at higher temperatures
• Factors affecting rate of diffusion


  • Temperature: Higher temperature increases rate of diffusion
  • Molecular mass: Lower molecular mass increases rate of diffusion
• Gases with lower molecular mass have greater rate of diffusion at the same temperature
• Reaction between aqueous ammonia and concentrated HCl


  • HCl molecules are heavier than NH3 molecules, so the white smoke (ammonium chloride) forms nearer to the HCl
• Element


  Made up of only one kind of atom, can exist as atoms or molecules, the basic unit of matter
• Types of elements


  • Metals
  • Non-metals
  • Metalloids
  • Noble gases
• Compound


  Combination of two or more elements, chemically bonded, has different properties from its component elements
• Molecule


  Two or more atoms of the same or different elements that are chemically bound together
• Mixture


  Combination of two or more elements or compounds, physically intermingled, can be separated by physical means
• Element


  The basic unit of matter, which cannot be broken down into substances by any way but can be combined to form new substances
• Types of elements


  • Metals
  • Non-metals
  • Metalloids
  • Noble gases
• Compound


  A combination of two or more elements, chemically
• Compounds


  • They are a pure substance
  • Can be broken down into a simpler type of matter (elements - metals) by chemical means (but not by physical means)
  • Have properties that are different from its component elements
  • Always contains the same ratio of its component atoms
• Compounds


  • Water
  • Carbon dioxide