Energy change in chemical reactions

Demonstrate understanding that exothermic and endothermic changes relate to the transformation of chemical energy to heat (thermal energy), and vice versa.

In order to actually start a reaction, a certain amount of energy will be provided to the reactants; We often call this the Energy of Activation because this energy is essentially required to start the reaction. The energy here is used to break the bonds between the molecules of the atoms of the reactants. The bonds then subsequently rearrange and bond again, which releases energy. However, if the energy provided to activate the energy is less than the energy released when the bonds form together, the reaction gave out more than it took/absorbed, which makes this a exothermic reaction. If the energy given to activate is more than the energy released during the bond formation, the reaction is endothermic. The total energy change is called enthalpy, but you don't really have to know that in IGCSE, I just thought it would be a nice to have.

Endothermic reaction

- Heat absorbs energy from the surroundings. - Temperature of surroundings decreases during an endothermic reaction because energy from surroundings is required to drive the reaction, hence decreasing the temperature of the surroundings.

Exothermic and Endothermic

During all chemical reactions, an energy change occurs. In the reaction, heat is either released or absorbed. When a reaction releases heat to the surroundings, we call that reaction an Exothermic Reaction. The reaction that absorbs energy from the surroundings are called Endothermic Reactions.

Exothermic reaction

The reactants have more energy than the products here, so a small amount of energy is required to activate the reaction - Release of heat - Energy needed for the reaction to occur is less than the total energy released. - Extra energy is released, usually in the form of heat. - The release of heat means that an exothermic reaction increases temperature of the surroundings.