SC 5.1

• Thermochemistry is the study about heat changes during chemical reaction

  Heat change in chemical reaction

  • Heat or energy change occurs in most of the chemical reaction
  • When a chemical reaction occurs, heat is absorbed or released
  • Heat is absorbed to break the bond in a compound. Conversely, the heat is release when the bond is formed
  • Chemical reaction can be classified into two types: Exothermic and Endothermic reaction
  • The chemical reaction are applied in the making of cold and hot packs
• Exothermic reaction

  • A reaction that releases heat to the surrounding (Solution)
  • When this reaction occurs, the reactant will releases heat to the surroundings
  • Since heat is released from the reactant to the surrounding, the surrounding temperature is increased
  • The contents in the container become hot. As a result, the container also feels hot when touched or shows a higher temperature when measure with a thermometer
  • The total energy content of the product is less than the total energy content of the reactants.
• Example of exothermic reaction

  • Burning of paper
  • Explosion of bomb
  • Adding / dissolving sodium hydroxide pellets in water
  • Neutralization
  • Respiration
  • Fireworks
  • Acid react with carbonate
• Endothermic reaction

  • A reaction that absorbs heat from the surrounding
  • When this reaction occurs, the reactant will gain heat from the surroundings
  • The contents in the container become cool. As a result, the container also feels cool when touched or shows a lower temperature when measured with a thermometer
  • The total energy content of the product is more than the total energy content of the reactant
• Example of endothermic reaction

  • Photosynthesis
  • Baking cake
  • Dissolving ammonium nitrate powder in water
  • Break down reactions of metal carbonates
  • Making instant cold packs