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Exothermic and Endothermic Reactions © Teachable. Some rights reserved.

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Presentation on theme: "Exothermic and Endothermic Reactions © Teachable. Some rights reserved."— Presentation transcript:

1 Exothermic and Endothermic Reactions © Teachable. Some rights reserved. http://teachable.net/res.asp?r=1910

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 © Teachable. Some rights reserved. http://teachable.net/res.asp?r=1910

3 Energy level diagrams Energy level Reaction progress Activation energy Energy given out by reaction Using a catalyst might lower the activation energy © Teachable. Some rights reserved. http://teachable.net/res.asp?r=1910

4 Endothermic process: a change (e.g. a chemical reaction) that requires (or absorbs) heat. Photosynthesis is an endothermic reaction (requires energy input from sun) Forming Na + and Cl - ions from NaCl is an endothermic process

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

6 Ammonium nitrate + water

7 Starting temperature 20 C

8 Add ammonium nitrate to water

9 a temperature decrease of 8 C

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

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

12 Exothermic vs endothermic: EXOTHERMIC – more energy is given out than is taken in (e.g. burning, respiration) ENDOTHERMIC – energy is taken in but not necessarily given out (e.g. photosynthesis) © Teachable. Some rights reserved. http://teachable.net/res.asp?r=1910

13 Examples Exothermic Combustion of fuels Yeast & Hydrogen Peroxide Epson salts & water Endothermic Photosynthesis Acedic Acid & Sodium Bicarbonate © Teachable. Some rights reserved. http://teachable.net/res.asp?r=1910


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