CHEMICAL REACTIONS
VACHS BIOLOGY
DO NOW:
1) What is a disaccharide?
2) What macromolecule do amino acids make
up?
3) Glycerol and fatty acids combine to make
what kind of macromolecule?
4) What is DNA composed of?
What is a chemical reaction?
Do we have any connections to the words
“chemical reactions?”
1. A chemical reaction is a process that changes
one set of chemicals into another.
2. Chemical reactions involve changes in the
chemical bonds that join atoms in compounds.
Examples of Chemical Reactions
Think/Pair/Share: Discuss any examples of
chemical reactions that you have performed or
that we have studied in this class.
3. Physical Reaction vs Chemical
Reaction
PHYSICAL REACTION: causes a phase change
(think of some examples…).
CHEMICAL REACTION: causes changes in
chemical bonds.
4. Burning Hydrogen Gas
2H2 + O2 -> 2H2O
Write this equation in words …
Cold Calls:
1) What are the reactants?
2) What is the product?
4. Burning of Hydrogen Gas
2H2 + O2 -> 2H2O
Write this equation in words …
Two molecules of hydrogen react with one
molecule of oxygen to make water!
Burning Hydrogen Gas
http://www.youtube.com/watch?v=WT5MGUyo
Txc
5. Think/Pair/Share: What kind of a reaction is
this? How do you know?
Energy Sources
6. What REACTION do plants
use to create their energy
source (glucose)?
7. How do animals obtain
their energy source (glucose)?
8. What reaction do both
plants and animals use to
make energy out of their
ENERGY SOURCES?
Breaking and Making Bonds
Breaking and Making Bonds
In the process of cellular respiration, both plants
and animals break down GLUCOSE and convert
it into energy.
9. The bonds are being broken in WHICH
MOLECULES?
C6H12O6 + O2 -> H2O + CO2
Breaking and Making Bonds
10. Breaking chemical bonds CREATES ENERGY.
Energy is released in the form of heat, so this is
an EXOTHERMIC REACTION.
11. Making chemical bonds REQUIRES ENERGY.
Energy is needed, so this is an ENDOTHERMIC
REACTION.
ACT IT OUT!!!
WHEN I SAY GO…..
Find a partner and link arms with them!
1. First demonstrate what happens to chemical
bonds during an exothermic reaction.
2. Then demonstrate what happens to chemical
bonds during an endothermic reaction!
Making and Breaking Bonds
THINK/PAIR/SHARE:
12. What kind of a reaction is cellular
respiration?
Making and Breaking Bonds
CELLULAR RESPIRATION IS EXOTHERMIC!!
The chemical bonds in the glucose and oxygen
molecules are being broken down to release
energy (heat!).
HOT AND COLD PACKS?
TWO VOLUNTEERS TO START THESE CHEMICAL
REACTIONS …
HOT AND COLD PACKS
HOT: EXOTHERMIC! You can feel the heat being
released.
COLD: ENDOTHERMIC! You can feel the loss of
heat.
Remember…. There is no “cold.” Only the
absence of heat!
Activation Energy
13. Activation Energy: the energy that is needed
to get a reaction started!
THINK/PAIR/SHARE: When you are burning
paper, what happens before it turns into smoke?
Activation Energy Diagrams
(…Diagram on the board. )
Label the Graphs: Endothermic or
Exothermic?
On the back of your paper…
Draw an activation energy diagram for CELLULAR
RESPIRATION.
Draw an activation energy diagram for
PHOTOSYNTHESIS.
Endothermic/Exothermic Lab
Voices/Movement: “restaurant voices,” one
person moves in order to get materials.
Instructions: Listen to the instructions I am
going to give and follow the instructions on your
lab sheets!
Success: Finish your lab, answer your questions
and clean up within the time allowed!
Finish Labs & Text Questions
Make sure to turn in your lab sheets at the front
of class and start working on your text support
questions!