Chapter 7

• physical change

  1. no new substances formed
  2. easy to reverse
  3. usually easy to seperate
  4. remain chemically same
• chemical change

  1. new substances formed
  2. difficult to reverse
  3. energy given out or taken in
  4. more exo reactions than endo
• exothermic is when energy is taken in from the surroundings into reaction
• endothermic is when energy is given out to the surroundings from reaction
• reaction pathway diagrams are used to demonstrate exo and endo reactions
• in RPD, exo's arrow will be downwards
• in RPD, endos arrow will be upwards
• in exothermic, the energy of reactant is more than energy of product
• in endothermic, the energy is reactant is less than energy of product
• making bonds is exothermic
• breaking bonds is endothermic
• bond energy is used to break covalent bonds
• endothermic is +ve
• exothermic is -ve
• enthalpy is the thermal heat content of a system