9) Chemical Energetics.pdf

CHEMICAL ENERGETICS (Energy Changes in Reactions) SCIENCE 9 Energy Changes in Reactions ❖ During a chemical reaction, there is always an energy change. ❖ Energy is taken out or taken in. ❖ Energy is usually in the form of heat. ❖ Reactions can be divided into two groups: 1. Exothermic 2. Endothermic...

CHEMICAL ENERGETICS (Energy Changes in Reactions) SCIENCE 9 Energy Changes in Reactions ❖ During a chemical reaction, there is always an energy change. ❖ Energy is taken out or taken in. ❖ Energy is usually in the form of heat. ❖ Reactions can be divided into two groups: 1. Exothermic 2. Endothermic EXOTHERMIC REACTIONS ❖ Can be described as: reactants -----> products + energy ❖ ❖ ❖ Total energy is the same on each side of the arrow, in a reaction Products have lower energy than the reactants Shown on the energy level diagram ---> ENDOTHERMIC REACTIONS ❖ Can be described as: reactants + energy -----> products ❖ ❖ ❖ Total energy is the same on each side of the arrow, in a reaction Since energy is taken in, products must have higher energy than the reactants Shown on the energy level diagram ---> EXPLAINING ENERGY CHANGES In a chemical reaction, bonds must first be broken. Then new bonds form. Breaking bonds takes in energy (endothermic). Making bonds releases energy (exothermic).