chemistry unit 7

• What is an exothermic reaction?


  A reaction that **releases heat** into the surroundings, causing the surroundings to warm up.
• What is an endothermic reaction?


  A reaction that **absorbs heat** from the surroundings, causing the surroundings to cool down.
• How does the energy change differ in endothermic vs. exothermic reactions?


  • Endothermic: Energy is **absorbed** (positive change).
  • Exothermic: Energy is **released** (negative change).
• bond breaking is endothermic as energy is taken in to break the bonds

  bond forming is exothermic as energy is released
• overall energy change = energy required to break bonds-energy released by forming bonds
• How does the reaction profile of an exothermic reaction look?


  The energy of the reactants is **higher** than the energy of the products. The curve falls from reactants to products, showing a **decrease in energy**.
• How does the reaction profile of an endothermic reaction look?


  The energy of the reactants is lower than the energy of the products. The curve rises from reactants to products, showing an increase in energy.
• What is activation energy?

  The **minimum energy** required for a chemical reaction to occur.
• What role do catalysts play in activation energy?

  Catalysts lower the activation energy, increasing the reaction rate without being consumed.
• How does activation energy affect reaction rate?

  **Higher activation energy** means a **slower reaction rate**, as fewer molecules have enough energy to react.
• What is the relationship between activation energy and temperature?

  **Increasing temperature** provides more energy to molecules, helping them overcome the activation energy barrier.
• How does **surface area** affect the rate of reaction according to collision theory?


  Increasing the surface area of a reactant increases the number of particles exposed and available for collisions, leading to a higher reaction rate.
• What is collision theory?


  Collision theory explains how chemical reactions occur and why reaction rates differ. It states that for a reaction to happen, particles must collide with sufficient energy and the correct **orientation**.
• What is the rate of reaction?


  The speed at which reactants are converted into products in a chemical reaction.
• average rate of reaction = amount of reactant used or amount of product formed / time
• the quicker a reaction takes place (shown by a fall or gain in mass) the quicker the rate of reaction is