Exo + endo reaction

• What changes occur during chemical reactions?

  Changes in energy occur
• What happens to temperature during chemical reactions?

  Temperature either heats up or cools down
• What is the principle of energy movement in chemical reactions?

  • Chemicals store different amounts of energy
  • Energy can be gained or lost during reactions
  • Energy is conserved; it cannot be created or destroyed
• What is an exothermic reaction?

  It transfers energy to the surroundings
• How is an exothermic reaction indicated?

  By a rise in temperature
• What is the best example of an exothermic reaction?

  Burning fuels (combustion)
• What type of reaction is neutralization?

  It is an exothermic reaction
• What happens when sodium is added to water?

  It releases energy and is exothermic
• What are some everyday uses of exothermic reactions?

  • Hand warmers using iron oxidation
  • Self-heating cans of beverages
• What is an endothermic reaction?

  It takes in energy from the surroundings
• How is an endothermic reaction indicated?

  By a fall in temperature
• What is an example of an endothermic reaction?

  Citric acid and sodium hydrogencarbonate reaction
• What happens during thermal decomposition?

  It absorbs heat to decompose substances
• What are some everyday uses of endothermic reactions?

  • Sports injury packs that cool instantly
• How can energy transfer be measured in reactions?

  • Measure initial temperature of reagents
  • Mix in a polystyrene cup
  • Measure final temperature after reaction
• What is a major problem with measuring energy changes?

  Energy lost to the surroundings
• How can you reduce energy loss during measurements?

  Use insulation and a lid on the cup
• How can you test the effect of acid concentration on energy released?

  1. Prepare different concentrations of HCl
  2. Mix with NaOH in a polystyrene cup
  3. Measure temperature changes
• What do reaction profiles show?

  • Relative energies of reactants and products
  • Energy changes during the reaction
• What variables can affect energy transfer in reactions?

  • Mass of reactants
  • Concentration of reactants
• What does an exothermic reaction profile indicate?

  Products are at lower energy than reactants
• What is activation energy?

  Minimum energy needed for reactants to collide
• What does a higher activation energy mean?

  More energy is needed to start the reaction
• What does an endothermic reaction profile indicate?

  Products are at higher energy than reactants
• What does the height difference in reaction profiles represent?

  • Overall energy change during the reaction
  • Energy absorbed or released per mole