Intro

• Chemistry: the study of matter; the physical science that deals with the composition, properties, and changes in matter
• Thermochemistry: the study of energy changes in a chemical reaction

  • Either endothermic or exothermic
• Law of conservation of energy: energy cannot be created or destroyed - only converted from one form of energy to another
• the chemical energy in food or hydrocarbons originated from the sun
• during photosynthesis, energy that originated from the sun is converted into chemical energy and stored in chemical bonds
• Hydrocarbon (fuels) process:

  1. Energy from the sun
  2. photosynthesis
  3. bacterial decay
  4. combustion
• Energy: a property of a substance or system that relates to its ability to do work
• Energy is measured in Joules (J) or kilojoules (kJ)
• 2 major types of energy:

  1. kinetic energy - to do with motion
  2. potential energy - stored
• breaking bonds requires energy, so the reaction is endothermic
• energy is released to form bonds, making the reaction exothermic
• Endothermic: energy needed to break bonds > energy released in forming bonds
• Exothermic: energy needed to break bonds < energy released in forming bonds
• an endothermuc reaction requires more energy than it releases, the energy must come from its surroundings. Energy released flows into surroundings
• Heat flows from hot to cold until equal
• 4.19 J/g °C -> 4.19 KJ/Kg °C
• photosynthesis is an endothermic reaction; it cannot occur without the sun
• when adding the same amount of energy to two similar massed samples, the substance with the larger specific heat capacity will have a smaller temperature change