1. Endothermic and Exothermic
Reactions

2. Energy and Reactions
Energy is involved in chemical reactions in two ways:
to break some (or all) bonds between atoms in the reactants so the atoms can form new bonds or
when the atoms or products form new bonds to make new products.

3. Two Types of Reactions
We classify chemical reactions based on how the energy of the reactants compares to the energy of the products.

4. Exothermic reactions
If forming new bonds releases more energy than it takes to break the old bonds, the reaction is exothermic.

5. Exothermic reactions
A good example is the reaction of hydrogen with oxygen.
Once started, exothermic reactions tend to keep going as each reaction releases more energy to fuel neighboring molecules.

6. Endothermic reactions
If forming new bonds in the products releases less energy than it took to break the original bonds, the reaction is endothermic.

7. Endothermic reactions
An important endothermic reaction is photosynthesis.
Plants need energy from sunlight to make glucose and oxygen from carbon dioxide and water.

8. EXOTHERMIC ENDOTHERMIC Exothermic Exothermic
Chemical reactions where HEAT…
Is transferred to the surroundings…
Indicated by a RISE in temperature
Chemical reactions where HEAT…
Is transferred from the surroundings …
Indicated by a FALL in temperature

9. Endothermic –
energy absorbed
melting
vaporization
sublimation

10. EXOTHERMIC-
Energy lost
freezing
condensation
deposition

11. Activation Energy
Activation energy is the energy needed to begin a reaction and break chemical bonds in the reactants.

12. Activation Energy
This is why a flammable material like gasoline does not burn without a spark or flame.

13. Examples of Endothermic Reactions
Most of the reactions used in industry to produce useful materials require more energy than they produce.
One process that uses endothermic reactions is the refining of ores to produce useful metals.

14. Examples of Endothermic Reactions
Most of the reactions used in industry to produce useful materials require more energy than they produce.
The reaction taking place inside an instant cold pack is endothermic.

15. Examples of Endothermic Reactions
When you squeeze the plastic bag the water reacts with the ammonium nitrate crystals, and the reaction dissolves the ionic bonds in the ammonium nitrate.

16. Examples of Endothermic Reactions

21. ACTIVITY
Complete graph
Matching with
Partner.

23. Very endothermic reaction with a big activation energy

25. Very exothermic reaction with a small activation energy

26. .

27. Moderately endothermic reaction with a
moderately high activation energy.

28. Could usually has a very low activation energy.
Energy level diagram for an exothermic chemical reaction without showing the activation energy. It could also be seen as quite exothermic with a highly unlikely zero activation energy, but reactions between two ions of opposite charge usually has a very low activation energy.
Could usually has a very low activation energy.

29. Exothermic without
Showing activation
energy

31. Moderately exothermic reaction with a moderately high activation energy

32. en as, probably impossible?).

33. Endothermic
Without activation
Energy being shown

34. Energy level diagram for an exothermic chemical reaction without showing the activation energy. It could also be seen as quite exothermic with a highly unlikely zero activation energy, but reactions between two ions of opposite charge usually has a very low activation energy.
Energy level diagram for an exothermic chemical reaction without showing the activation energy. It could also be seen as quite zero activation energy, but reactions between two ions of opposite charge usually has a very low activation energy.

35. Energy is
equal. Possible
But not likely

36. Create a
SONG
POEM
DRAWING to explain
The difference between
Endothermic and
Exothermic reactions.
Pg. 86 in book.

37. Explain the difference
Between endo and exo
Reactions.
2. Draw a graph of each
Type. Endo and exo
Label each
3. Write an equation for each

38. Words to be used
Endothermic
Exothermic
Activation energy
Absorbed
Released