Chemistry

• Solids


  • Particles have a regular arrangement and are close together
• Liquids


  • Particles have a random arrangement and are close together
• Gases


  • Particles have a random arrangement and are spread apart
• Melting and freezing


  Take place at the melting point
• Boiling and condensing


  Take place at the boiling point
• Particle model


  Particles are represented by small solid spheres
• Gas particles


  Have the most energy, shown by being the most spread apart, with more random and frequent motion
• Liquid particles


  Have more energy than solids, but less than gases
• Solid particles


  Have the least energy, not moving/just vibrating
• Evaporation


  Happens at the surface, molecules have enough energy to evaporate (liquid to gas)
• Freezing


  Liquid to solid
• Melting


  Solid to liquid
• Boiling


  Happens throughout the liquid, liquid to gas
• Condensation


  Gas to liquid
• Sublimation


  Solid to gas
• Changes of state are physical changes, involving the forces between the particles of the substances
• Kinetic theory


  Can help explain melting, boiling, freezing and condensing
• The amount of energy needed to change state depends on the strength of the forces between the particles
• The nature of the particles involved depends on the type of bonding and the structure of the substance
• The stronger the forces between the particles, the higher the melting point and boiling point
• The more kinetic energy (from increased temperature) particles have, the more movement, causing changes of state
• Higher pressure


  More motion of a gas' particles
• Higher temperature


  More motion of a gas' particles
• Particles in liquids and gases move randomly (Brownian motion)
• Brownian motion happens because particles collide with other moving particles in the fluid
• Brownian motion is evidence for the kinetic particle model of matter
• Brownian motion


  Random molecular bombardment causes larger particles to move randomly in a fluid
• Robert Brown observed the random movement of pollen grains in water, showing there were separate particles moving randomly
• Diffusion


  Movement of particles from an area of high concentration to an area of low concentration
• Diffusion does not occur in solids, since the particles cannot move from place to place (only vibrate)
• Smells do not travel very fast, because the particles collide with air particles, changing direction randomly
• Smaller molecular mass


  Greater average speed of the molecules, therefore faster gas diffusion
• Solvent

  Liquid in which a solute dissolves
• Element


  Substance made from only one type of atom
• Compound


  Substance made from two or more elements that have reacted chemically with each other
• Mixture


  • Consists of 2 or more elements or compounds not chemically combined together
  • Chemical properties of each substance in the mixture are unchanged
• Metals


  • Elements that react to form positive ions
  • Found to the left and towards the bottom of the periodic table, they lose electron(s) in order to form these positive ions
• Ion


  An atom or group of atoms with a positive or negative charge
• Single covalent bond


  The sharing of pairs of electrons leading to the noble gas configuration
• Symbols of the elements

  How the elements are shown in the periodic table (e.g. Sodium (Na), Chlorine (Cl))