C5.1 Exothermic and endothermic reactions

What is an exothermic reaction + examples?

• A chemical reaction that transfers energy to its surroundings, leading to an increase in temperature of the surroundings

• Examples: combustion, respiration

What is an endothermic reaction + examples?

• A chemical reaction that absorbs energy from its surroundings, leading to a decrease in temperature of the surroundings

• Examples: photosynthesis, melting ice

In which reaction are the products more stable and in which are the reactants more stable?

• Reactants are more stable in endothermic reactions

• Products are more stable exothermic reactions

What is the transfer of thermal energy during a reaction called?

• Enthalpy change, represented by ∆H

  • In exothermic reactions: -∆H

  • In endothermic reactions: ∆H

What is activation energy (E_a)?

• The minimum energy colliding particles must have to react

Draw and label a reaction pathway diagram for exothermic reactions

Draw and label a reaction pathway diagram for endothermic reactions

What type of reaction is bond making?

• Bond making: exothermic process

  • Bonds release energy into surroundings to achieve a stable configuration

What type of reaction is bond breaking?

• Bond breaking: endothermic process

  • Bonds absorb energy to be able to have enough to break apart atoms held together by intermolecular forces