In order for a chemical change to occur there must be energy transferred to or from it’s surrounding, with a usual occurrence of temperature change. In this experiment we had the opportunity to test and observe different solutions in order to determine their type chemical reaction, and as the experiment went on we noticed multiple recurring characteristics in each solution which provided us with aid to determine the reaction. Through this experiment, we were able to determine that exothermic reactions occur when heat moves out of the system into its surrounding, hence, causing an increase in the temperature and and a negative sign of heat. This is a result of the bond energies of the reactants being less than the bond energies of the products, consequently, less energy is required to break the bonds in contrast to the energy released during the formation of the bonds. The reason that the exothermic reaction sign of heat is negative is because the enthalpy of the products is lower than the enthalpy of the reactants of the system. We were also able to determine that endothermic reactions occur when heat moves from its surroundings into the system, in other words causing a temperature decrease – causing the mixture to become colder, and have a positive sign of heat. This is due to the larger amount of energy required to break the bonds than the amount of energy needed to form the bonds in the first place. In this case the energy usually is in the form of heat, therefore, when the heat is absorbed from its surrounding the temperature decreases. An example of this would be photosynthesis, which is a great example as it clearly demonstrates the process of absorbing the energy from its surrounding, which in this case would be energy from the sun to convert carbon dioxide and water into glucose and oxygen, which requires more energy to make than that released. An example of an exothermic reaction would be freezing, because you are transforming the liquid to a solid, therefore, causing bonds to form, which means that you are giving off energy. Because the exothermic reactions are giving out the energy to the surrounding, the energy of the reactants is higher, and the energy of the products are lower.