energetics

• Why do chemical reactions occur?

  To achieve a more stable energy state
• What is the purpose of chemical bonding in reactions?

  To break old bonds and form new ones
• What does the process of chemical reactions involve?

  Transfer of energy into and out of mixtures
• What are the two terms used to describe energy in chemical reactions?

  System and surroundings
• Where does the energy in chemical reactions come from?

  From the chemical bonds themselves
• What form of energy is most commonly produced in reactions?

  Heat energy
• What happens in exothermic reactions?

  Energy is given out to the surroundings
• How does the temperature of surroundings change in exothermic reactions?

  The temperature increases
• What are typical examples of exothermic reactions?

  Combustion, oxidation, and neutralisation
• How are hand warmers related to exothermic reactions?

  They release heat from an exothermic reaction
• What is the effect of endothermic reactions on the surroundings?

  They decrease the temperature of the surroundings
• What are typical examples of endothermic reactions?

  Electrolysis and thermal decomposition
• How do cold packs utilize endothermic reactions?

  They take heat away to prevent swelling
• How can changes in heat content be measured?

  With a thermometer or temperature probe
• What does the conservation of energy in reactions imply?

  Energy cannot be created or destroyed
• What happens to the energy of products compared to reactants in exothermic reactions?

  Products have less energy than reactants
• What is activation energy?

  The minimum energy required for a reaction
• What factors influence the success of collisions in chemical reactions?

  Energy, orientation, and collision frequency
• How do reactions with higher activation energies compare to those with lower activation energies?

  They require more energy to start
• What do reaction profiles represent?

  Relative energies of reactants and products
• What does the y-axis represent in a reaction profile?

  The energy of reactants and products
• What does the height difference in a reaction profile indicate?

  The overall energy change of a reaction
• What do arrows in reaction profiles indicate?

  Whether the reaction is exothermic or endothermic
• What does the initial rise in energy in a reaction profile represent?

  The activation energy required to start the reaction
• What does a greater initial rise in a reaction profile indicate?

  More energy is required to start the reaction
• reaction profile - exothermic reaction

  exothermic reaction

  A) activation energy

  B) overall energy change

  C) products

  D) progress of reaction

  
• reaction profile

  endothermic reaction

  A) activation energy

  B) overall energy change

  C) products