1. Exothermic and Endothermic Reactions
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2. Endothermic and exothermic reactions
Step 1: Energy must be SUPPLIED to break chemical bonds:
Step 2: Energy is RELEASED when new chemical bonds are made:
A reaction is EXOTHERMIC if more energy is RELEASED than SUPPLIED. If more energy is SUPPLIED than is RELEASED then the reaction is ENDOTHERMIC
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3. Forming Na+ and Cl- ions from NaCl is an endothermic process
Endothermic process: a change (e.g. a chemical reaction) that requires (or absorbs) heat.
Forming Na+ and Cl- ions from NaCl is an endothermic process
Photosynthesis is an endothermic reaction (requires energy input from sun)

4. Measuring Heat
reaction
Endothermic reaction, heat taken in & temperature of the substance drops

5. EXOTHERMIC & ENDOTHERMIC REACTIONS
Exothermic process: a change (e.g. a chemical reaction) that releases heat.
Burning fossil fuels is an exothermic reaction

6. Exothermic reaction, heat given off & temperature of substance rises.
Heat Released
reaction
Exothermic reaction, heat given off & temperature of substance rises.