Transcript Lesson 3

Reviewing Chemical
Reactions
Remember This?
Two parts of a chemical reaction:
2 Na
+ Cl2
2 NaCl
Products [the
substances
produced]
Reactants [enter/s reaction]
2 H2O2
Which is which?
2 H2O
+ O2
LAW OF CONSERVATION OF
MASS:
“Matter is neither created NOR
destroyed in a chemical
reaction. Atoms just get
REARRANGED!”
A + BC
AC + B
Whatever atom is found in the REACTANT
side MUST exist in the PRODUCT side! No
atom is lost or destroyed! No mass is gained or
lost!
The amount
that goes in
MUST
balance the
amount of
products
produced!
A
+
20 g
B
50 g
AB
? grams
So where did it go?
• Wood was burned
and ash collected.
• All the ash collected
did not balance the
reactants used up!
• Why?
WOOD + Oxygen
500 g
ASH
150 g
ENERGY IN REACTIONS
Endothermic Reactions
Exothermic Reactions
The reaction absorbed
Energy.
The reaction releases
Energy.
Energy Diagrams
The reactants
possess a
lower energy
content than
the products.
Energy must
have been
absorbed!
Energy
content of
the
products is
lower than
the energy
of the
reactants.
Energy must
have been
released!
Exothermic Reaction Energy
Diagram
I knew that!