Endothermic Exothermic Reactions 1 Endothermic process Heat flows

Endothermic & Exothermic Reactions 1

Endothermic process Heat flows into the system from the surroundings in an endothermic process. Surroundings Cold pack Energy Temperature falls

Exothermic process Heat flows into the surroundings from the system in an exothermic process. Surroundings Energy Hot pack Temperature rises

Energy Level Diagrams Endothermic reactions products energy reactants The products are higher in energy than the reactants energy taken in is positive time of reaction

Energy Level Diagrams Exothermic reactions energy reactants Energy given out is negative products Time of reaction The products are lower in energy than the reactants

Exothermic reactions The products have less energy than the reactants. The energy is given out to the surroundings. The temperature goes up.

Endothermic reactions The products have more energy than the reactants. The energy is taken in from surroundings. The temperature goes down.

Units of Energy 1 calorie = heat required to raise temp. of 1. 00 g of H 2 O by 1. 0 o. C. 1 kcal = 1 Calorie (a food “calorie”) But we use the unit called the JOULE 1 cal = 4. 184 joules w. James Joule w 1818 -1889

Breaking & Making Bonds Breaking Bonds always requires energy, so the process is endothermic Making Bonds gives off energy, so the process is exothermic

Energy (in Joules) C 4 H 4 O w. Step 1 w. Step 2 CH 4 + 2 O 2 w. Step 1: Breaking Bonds (Endothermic) w. Step 2: Making Bonds (Exothermic) CO 2 + 2 H 2 O