Csec Chemistry

• What is Chemistry

  The study of the composition, structure, properties and reactions of matter
• What is Matter

  Anything that has volume and mass
• What are the States of matter

  • Solid
  • Liquid
  • Gas
• Particulate theory of matter

  • All matter is composed of particles
  • The particles are in constant motion and temperature affects their speed of motion
  • The particles have empty spaces between them
  • The particles have forces of attraction between them
• What is Diffusion

  Particles move from a region of higher concentration to a region of lower concentration, until the particles are evenly distributed
• Diffusion example 1


  • Ammonia gas and hydrogen chloride gas collide and react to form ammonium chloride
• Diffusion example 2


  • Potassium manganate(VII) crystal dissolves in water, particles separate and diffuse evenly
• What is Osmosis

  The movement of water molecules through a differentially permeable membrane from a solution containing a lot of water molecules to a solution containing fewer water molecules
• Acids have more H+ than OH- ions, resulting in a lower pH value.
• Metallic bonds occur in metals where electrons are delocalized and free to move.
• A solution with a pH of 7 is neutral (neither acidic nor basic).
• A solution with a pH of 7 is neutral because it contains equal amounts of hydrogen (H+) and hydroxide (OH-) ions.
• Covalent bonds involve the sharing of electrons between two non-metal atoms.
• Membranes of living cells


  • Differentially permeable
  • Cytoplasm contains about 80% water
• What happens when a strip of living tissue is placed in water

  1. Water molecules move into the cells by osmosis

  2. Each cell swells slightly

  3. The strip increases in length and becomes rigid
• What happens when the strip is placed in a concentrated sodium chloride solution


  1. Water molecules move out of the cells by osmosis

  2. Each cell shrinks slightly

  3. The strip decreases in length and becomes softer
• Uses of osmosis

  • To control garden pests (slugs and snails)
  • To preserve food (using salt and sugar)
• Atoms


  Smallest units of a chemical element which have all the characteristics of the element
• Molecules


  Groups of two or more atoms bonded together and which can exist on their own
• What are Ions

  Electrically charged particles, may be formed from a single atom or groups of two or more atoms bonded together
• Types of particles that make up matter


  • Atoms
  • Molecules
  • Ions
• Solid


  • Fixed shape
  • Fixed volume
  • High density
  • Difficult to compress
  • Particles packed closely together in a regular way
  • Strong forces of attraction between particles
  • Particles vibrate in fixed positions
• Liquid


  • Takes the shape of the container
  • Fixed volume
  • Lower density than solids
  • Can be compressed slightly
  • Particles randomly arranged with small spaces between
  • Weaker forces of attraction between particles
  • Particles move slowly past each other
• Gas


  • Takes the shape and volume of the container
  • Low density
  • Very easy to compress
  • Particles randomly arranged with large spaces between
  • Very weak forces of attraction between particles
  • Particles move around freely and rapidly
• Changing state


  1. Heating a solid causes it to change to a liquid and then a gas as particles gain kinetic energy, move faster and forces of attraction weaken

  2. Cooling a gas causes it to change to a liquid and then a solid as particles lose kinetic energy, move slower and forces of attraction strengthen
• Evaporation


  Can occur at any temperature, only at the surface of the liquid
• Boiling


  Occurs at a specific temperature, throughout the liquid
• Sublimation


  Solid changes directly to gas
• Deposition


  Gas changes directly to solid
• Heating curve


  Plots temperature against time as a solid is heated and changes state to liquid and gas
• Cooling curve


  Plots temperature against time as a gas is cooled and changes state to liquid and solid
• Melting point


  Constant temperature at which a solid changes to a liquid
• Boiling point


  Constant temperature at which a liquid changes to a gas
• Freezing point


  Constant temperature at which a liquid changes to a solid
• The melting and freezing points of any pure substance have the same value
• - Diffusion - particles move from an area of high concentration to low concentration until they are evenly distributed throughout the space available (diffuse)
• Osmosis - diffusion through a semipermeable membrane, e.g., cell membranes or dialysis tubes.
• Diffusion - particles move from an area of high concentration to low concentration until they are evenly distributed throughout the space available (diffuse)
• Evidence to support the particulate theory of matter:

  Osmosis

  Diffusion

  Crystals have a regular shape

  Crystals dissolve
• Distillation is used to separate liquids with different boiling points.