Endo and exothermic reactions

• What happens to energy during chemical reactions?

  Energy is conserved.
• What does it mean that energy is conserved in chemical reactions?

  The amount of energy in the universe remains the same before and after a reaction.
• What occurs to the energy of product molecules in an exothermic reaction?

  Product molecules have less energy than the reactants by the amount transferred.
• What is an exothermic reaction?

  An exothermic reaction transfers energy to the surroundings, increasing their temperature.
• Can you name some examples of exothermic reactions?

  Combustion, many oxidation reactions, and neutralization.
• What are everyday examples of exothermic reactions?

  Self-heating cans and hand warmers.
• What is an endothermic reaction?

  An endothermic reaction takes in energy from the surroundings, decreasing their temperature.
• What happens to the energy of product molecules in an endothermic reaction?

  Product molecules have more energy than the reactants.
• Can you name some examples of endothermic reactions?

  Thermal decomposition and the reaction of citric acid with sodium hydrogencarbonate.
• What are some applications of endothermic reactions in everyday life?

  Some sports injury packs are based on endothermic reactions.
• What is required for chemical reactions to occur?

  Reacting particles must collide with each other with sufficient energy.
• What is activation energy?

  Activation energy is the minimum amount of energy that particles must have to react.
• What can reaction profiles show about chemical reactions?

  • Relative energies of reactants and products
  • Activation energy
  • Overall energy change of a reaction

  
• How can you determine if a reaction is exothermic or endothermic from a reaction profile?

  You can tell by looking at whether the reactants or products have more energy.

  
• What characterizes an exothermic reaction in terms of energy transfer?

  Heat is released to the surroundings, so products have less energy than reactants.
• What characterizes an endothermic reaction in terms of energy transfer?

  Heat is taken in from the surroundings, so products have more energy than reactants.
• What happens to energy during a chemical reaction when bonds are broken and formed?

  Energy must be supplied to break bonds and is released when bonds are formed.
• How can the overall energy change of a reaction be calculated?

  By subtracting the sum of energy released to form bonds from the sum of energy taken in to break bonds.
• What indicates an endothermic reaction in terms of energy calculations?

  Energy taken in to break bonds is greater than energy released when formed.

  
• What indicates an exothermic reaction in terms of energy calculations?

  Energy taken in to break bonds is less than energy released when formed.

  
• What are the key differences between exothermic and endothermic reactions?

  Exothermic Reactions:

  • Release energy to surroundings
  • Temperature of surroundings increases
  • Products have less energy than reactants

  
  

  Endothermic Reactions:

  • Absorb energy from surroundings
  • Temperature of surroundings decreases
  • Products have more energy than reactants