The document discusses endothermic and exothermic reactions. It defines endothermic reactions as those that require energy input to occur, while exothermic reactions release energy. Specific examples are given of endothermic processes like photosynthesis and forming NaCl ions, and exothermic processes like burning fossil fuels. Methods for measuring the temperature change of reactions to determine if they are endothermic or exothermic are also outlined.

1. Exothermic and Endothermic
Reactions
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By,
Abhinav.B

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. Energy level diagrams
Energy
level
Reaction progress
Activation
energy
Energy given
out by
reactionUsing a catalyst
might lower the
activation energy
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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 HeatMeasuring Heat
reaction
EndothermicEndothermic
reaction, heatreaction, heat
taken in &taken in &
temperature oftemperature of
the substancethe substance
dropsdrops

6. Ammonium nitrate + water

7. Starting temperature 20 C⁰

8. Add ammonium nitrate to water

9. a temperature decrease of 8 C⁰

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

11. Heat Released
ExothermicExothermic
reaction, heatreaction, heat
given off &given off &
temperature oftemperature of
substancesubstance
rises.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)
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13. Examples
Exothermic
• Combustion of fuels
• Yeast & Hydrogen
Peroxide
• Epson salts & water
Endothermic
• Photosynthesis
• Acedic Acid &
Sodium Bicarbonate
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