Y9.5

• Liquids


  No fixed shape, can be poured, can be stirred, can be squashed
• Gases


  No fixed shape or volume, can be poured, can be stirred, can be squashed
• Solids


  • Strong forces of attraction, held in fixed position, lattice arrangement, don't move so have definite shape and volume, vibrate, expand when heated, can't be compressed, generally very dense
• Liquids


  • Some attraction between molecules, free to move, no definite shape but take shape of container, molecules in constantly random motion, expand when heated, can't be compressed, quite dense
• Gases


  • No force of attraction, free to move and travel in straight lines, sometimes collide, no definite shape or volume, expand to fill space, exert pressure, constantly moving randomly, move faster when heated, can be compressed, very low densities
• Changes of State


  1. Melting

  2. Boiling (evaporating)

  3. Condensing

  4. Freezing
• Heating Curve


  Graph of temperature against time showing changes of state
• When the process of melting begins, the temperature remains constant, even though heat is constantly being supplied. This is because the energy absorbed during the melting process is equal to the energy released during the same. Thus, no change in temperature is observed.
• Cooling Curve


  Graph of temperature against time showing changes of state during cooling
• When heat is taken out of the system, which holds water vapor, the temperature gradually drops. A constant record of temperature gives us the cooling temperature where the vapor changes to its liquid form, while further minimization of heat will give us the value of the freezing point for the water cooling curve.
• The reading of a cooling curve is achieved in the same way as a labeled heating curve where the constant value of temperatures give us the values of the cooling and freezing points of a particular substance.
• Energy is absorbed and released during changes of state
• Heating curve including plasma state
• Kinetic Theory of Matter

  All matter is made up of atoms and molecules that are always in motion, which we perceive as temperature
• Higher temperature


  Particles move faster
• More massive particles


  Move slower than less massive ones
• All particles of matter have kinetic energy because they are in motion
• Physical state of a compound

  Determined by temperature, kinetic energy, and intermolecular forces
• Intermolecular forces


  Forces, other than chemical bonds, that tend to attract two molecules to each other
• Diffusion


  Movement of molecules in a fluid from areas of high concentration to areas of low concentration

  
• Conditions required for diffusion to readily occur


  Factors that affect rate of diffusion

  
• Molecular mass


  Heavier molecules move more slowly and diffuse more slowly, lighter molecules move faster and diffuse more quickly
• Higher temperature


  Increases the energy and movement of molecules, increasing the rate of diffusion
• Brownian motion


  Particles in a fluid move around in random directions and collide with each other and their surroundings, causing them to change direction and spread out or diffuse through the liquid
• Evidence for Brownian motion

  • Observation of pollen grains in water being randomly bombarded by water molecules (Einstein)
  • Observation of smoke particles under a microscope moving randomly due to collisions with smaller unobservable particles

  
• Compound


  A pure substance made up of two or more different elements chemically combined in a fixed proportion
• Mixture


  A physical combination of two or more substances that are not chemically combined
• Matter can be classified as pure substances or mixtures
• Types of pure substances

  • Elements
  • Compounds
• Types of mixtures


  • Homogeneous
  • Heterogeneous

  
• Homogeneous mixture


  A mixture with a uniform composition throughout
• Heterogeneous mixture


  A mixture with a non-uniform composition

  
• Solution


  Another word for a homogeneous mixture
• Parts of a solution

  • Solvent
  • Solute
• Solvent


  The substance that dissolves the solute
• Solute


  The substance that is being dissolved
• Aqueous solution


  A solution in which water is the solvent
• Filtration


  Separation method used to separate out pure substances in mixtures made up of particles some of which are too large to pass through the filter
• Common use of filters

  • Air conditioners have filters that allow air to pass through while trapping solids such as lint and dust
• Distillation


  Procedure by which a solid and a liquid, or two liquids with different boiling points can be separated, using the process of evaporation and condensation