Changes around us, Heat, light, catalyst

3. •Chemical reaction based on heat.
•Chemical reaction based on light.
•Chemical reaction based on
catalyst.

4. CHEMICAL REACTION BASED ON HEAT
RAW FOOD
HEAT
COOKED FOOD

5. Lead Nitrate
Heating
Evolution of Reddish brown gas
(Nitrogen dioxide)
Laboratory experiments

6. Limestone
Industry
Heating
Quick lime

7. Hence, some of the chemical
reactions can be achieved by
the supply of heat only.
These reactions are called
thermo chemical reactions or
thermolysis.

8. Evolution of heat energy Absorption of heat energy

9. Chemical reactions based on light
What will happen if there is no
sun light?
All the human activities will
be affected and there will be no
food for us to survive.

10. Photosynthesis
Green plants prepare their own food with the help of carbon di oxide
and water in the presence of sunlight is called photosynthesis
STARCH

11. Chemical reactions which take place by the
action of light is called Photo chemical reaction.

12. Chemical reaction based on catalyst.
Idly batter
Yeast
Sour taste batter
FERMENTATION
SIMPLER PRODUCTS
(IDLY)

13. The enzymes released by yeast
makes the reaction faster. Like this,
in industries some chemical
substances are used to alter the
speed of the chemical reaction.
These substances are called catalyst.

14. Example:
Metallic iron is used as a
catalyst in the manufacture of
ammonia using Haber process.
This Ammonia is the basic
material for the production of
Urea, an important fertilizer in
agriculture

15. Thus, speed of the certain
reactions is influenced by
the catalysts and such
reactions are called
catalytic reactions.

16. ASSIGNMENT
1. What are thermo chemical reactions?
2. Define exothermic reactions.
3. Define photochemical reactions.
4. What are catalysts?