Endothermic and Exothermic Reactions

Target Language or Knowledge:

During a chemical reaction what is always transferred? - Energy Described what is meant by the "conservation of energy" - In a chemical reaction energy cannot be created or destroyed. How is energy transferred in chemical reactions? - Through the breaking of chemical bonds in the reactants and creating new bonds in the products What name is given to reactions that transfer energy to the surroundings? - Exothermic How do you know that an exothermic reaction has taken place? - Through an increase in temperature from the reactants to the products. What is the name given to chemical reactions that transfer energy from the surroundings to the reactants? - Endothermic Name 2 examples of an exothermic reaction. - oxidation, combustion, respiration or neutralisation Name 2 examples of an endothermic reaction - photosynthesis, sodium hydrogen-carbonate and citric acid or thermal decomposition What is meant by the term "thermal decomposition"? - To break down with heat. If a reaction gives out energy to the surroundings, what happens to the energy of the products? - The energy of the products will be less. Not every collision between particles results in a chemical reaction. Why? - Not all particles collide with enough energy to cause a reaction. What investigation would you do to find out if a reaction is endothermic or exothermic? - Record initial temperature of reactants and the final temperature to find a temperature difference. When you put sherbet into your mouth your mouth feels slightly cool. Why? - During this reaction heat is being removed from the surroundings. What is a compound? - Substance made when two or more elements combine through chemical bonding. What does pH7 mean? - The solution is neutral, neither an acid or an alkali What is meant by the term "oxidation"? - A chemical reaction where oxygen is added to a substance, or when electrons are lost from a substance. What is meant by a "reversible" reaction? - A reaction that can revert back to the original reactants. What is meant by the product of a chemical reaction? - The chemical produced as a result of a chemical reaction. What is meant by the "reactants" in a chemical reaction? - The chemicals that you start off with, before the reaction takes place. What is meant by "bond energy"? - The amount of energy needed to break a particular chemical bond.

Energy created destroyed reactants products Exothermic increase Endothermic combustion respiration photosynthesis heat less collide energy temperature temperature temperature removed bonding acid alkali oxidation reversible product reactants bond energy