C5

• State the law of conservation of energy.

  Energy cannot be created or destroyed, it can only transferred from one place to another.
• How does the law of conservation of energy apply to chemistry?


  In all chemical reactions, energy is either transferred to the surroundings or from the surroundings.
• What is an exothermic reaction?


  A reaction where energy is transferred to the surroundings.
• Give two examples of exothermic reactions.

  Combustion, respiration
• What happens to the temperature of the surroundings during an exothermic reaction?

  They increase. The thermometer is included in "the surroundings" so shows the temperature increasing.See an expert-written answer!We have an expert-written solution to this problem!
• What is an endothermic reaction?


  A reaction where energy is transferred from the surroundings.
• Give two examples of endothermic reactions.

  Thermal decomposition reactions, citric acid and sodium hydrogencarbonate.
• What happens to the temperature of the surroundings during an endothermic reaction?

  They decrease. The thermometer is included in "the surroundings" so shows the temperature decreasing.See an expert-written answer!We have an expert-written solution to this problem!
• State two uses of exothermic reactions

  Self-heating cans, hand warmers
• State two uses of endothermic reactions

  Some cooling sports injury packs
• What are reactants?

  The substances involved in a chemical reaction
• What are products?

  The substances formed when reactants have a chemical reaction
• What is a reaction profile?

  A diagram which shows whether the reactants have more or less energy than the products.
• If the reactants have more energy than the products, what kind of a reaction must have taken place?

  An exothermic one. The missing energy has been transferred to the surroundings.
• If the reactants have less energy than the products, what kind of a reaction must have taken place?

  An endothermic one. The extra energy has been take in by the surroundings.See an expert-written answer!We have an expert-written solution to this problem!
• Is breaking bonds endothermic or exothermic?

  Endothermic. Chemical bonds are strong so require energy to break (like when you have to put energy in to separate magnets from each other)
• Is making bonds endothermic or exothermic?

  Exothermic. Energy is released when chemical bonds are formed (like how two magnets move together when close and generate kinetic energy)
• How do we work out the overall energy change of a reaction?

  Work out the difference between the energy needed to break all the bonds in the reactants and the energy released to form all the bonds in the products.