Energy change

• what is the conservation of energy principle?

  Energy is conserved in chemical reactions. The amount of energy in the universe at the end of chemical reactions is the same as before it takes place.
• What’s an exothermic reaction?

  A reaction where energy is transferred to the surroundings so that the surrounding temperature increases. They have by a negative sign of energy change.
• Examples of exothermic reaction.

  combustion, oxidation reactions and neutralisation reactions.
• What are endothermic reactions?

  Reactions where energy is taken from the surroundings so the temperature decreases. They have a positive sign of energy change.
• Give some examples of an endothermic reaction.

  Thermal decomposition, reaction of citric acid and sodium hydrogencarbonate.
• What is activation energy?

  Activation energy is the minimum amount of energy required for particles to react.
• what’s a reaction profile?

  A graph showing the relative energy changes of reactants and products as well as the activation energy of a reaction.
• In terms of bonds, what occurs in a chemical reaction?

  Energy is supplied to break bonds and energy is released when bonds are made.
• Describe exothermic reactions in terms of bond breaking.

  Energy released from forming bonds is greater than that needed to break the bonds.
• Describe endothermic reactions in terms of bond breaking/forming.

  Energy needed to break bonds is greater than energy released making them.
• whats the equation to find energy of a reaction?

  Energy of reaction = sum of broken bonds - sum of bonds made.
• What’s a cell?

  A cell is composed of two electrodes dipped in an electrolyte solution. It produces electricity from a chemical reaction.
• What’s a battery?

  A battery consists of two or more cells connected in series.