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UNIT 2: CELLS AND ENERGYIs it ethical to water plants in the midst of a drought?
Catalyst
Which of the following is a chemical reaction?
1. rusting of iron
2. chopping wood
3. breaking a glass
4. mixing baking soda and vinegar
5. Shredding a piece of paper
6. baking a cake
7. crushing a can
8. melting an ice cube
9. mixing sand and water
10. cooking an egg
11. dissolving sugar and water
12. burning wood
Decomposition of Hydrogen Peroxide
H2O2 H2O + O2 + heat
Elephant Toothpaste
Every table needs:
Trash bag
Glasses for each person
Beaker
Straw
Once everyone is gloved has their glasses on, send someone to Ms. Adabale to get:
½ cup hydrogen peroxide in a bottle
Food coloring
Dish soap
Warm water
Go to your table and wait for further instructions!
Chemical Reactions
1. Chemical Reaction: process by which atoms or compounds are reorganized into different atoms/compounds.
2. Photosynthesis Reaction
6CO2 + 6H2O + Light C6H12O6 + 6O2
C
C
C
C
C
C
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
H
H
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
3. Chemical Reactions
Clues that a chemical reaction has taken place: Something new is visibly produced
Example: baking a cake
A gas is created
Example: baking soda and vinegar
Heat is given off or taken in
Example: thermite reaction
http://www.youtube.com/watch?v=o8gapa8ibK0
Reevaluate your list!
1. rusting of iron
2. chopping wood
3. breaking a glass
4. mixing baking soda and vinegar
5. Shredding a piece of paper
6. baking a cake
7. crushing a can
8. melting an ice cube
9. mixing sand and water
10. cooking an egg
11. dissolving sugar and water
12. burning wood
Chemical Reactions
1. rusting of iron
2. chopping wood
3. breaking a glass
4. mixing baking soda and vinegar
5. Shredding a piece of paper
6. baking a cake
7. crushing a can
8. melting an ice cube
9. mixing sand and water
10. cooking an egg
11. dissolving sugar and water
12. burning wood
4. Reactants and Products
Photosynthesis Reaction:
6CO2 + 6H2O + Light C6H12O6 + 6O2
The arrow always points from reactants to products.
Reactants(Starting Substances)
Products(Formed Substances)
5. Activation Energy
Activation Energy: minimum amount of energy (usually heat) required to start a reaction.
***For both reactions, activation energy is measured from reactants to peak.
Reaction Progress
Energy
Reactants
Products
XY
X+Y
ActivationEnergy
Products can absorb
energy
Reaction Progress
Energy
Reactants
Products
XY
X+Y
ActivationEnergy
Products can release energy
Products that release energy feel HOT (exothermic)
Products that absorb energy feel COLD (endothermic)
Catalyst
If a reaction doesn’t get enough activation energy, it can’t start!
2 Options
Add more energy
Lower activation energy
Catalyst: Lowers activation energy of a chemical reaction resulting in a faster reaction rate
Reaction Progress
Energy
Reactants
Products
XY
X+Y
Without Catalyst
With Catalyst
Think about it…
Why does Ms. Adabale call warm-ups catalysts?
Thinking Back…
What were the reactants?
What were the products?
Was the reaction endothermic or exothermic?
Was there a catalyst? If so, what?
How do you think changing the amount of hydrogen peroxide would alter the experiment? Yeast?
