UNIT 2: CELLS AND ENERGY Is 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  H 2 O 2 H 2 O + O 2 + 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 6CO 2 + 6H 2 O + Light  C 6 H 12 O 6 + 6O 2 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

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:  6CO 2 + 6H 2 O + Light C 6 H 12 O 6 + 6O 2  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 Activation Energy Products can absorb energy Reaction Progress Energy Reactants Products XY X+Y Activation Energy 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?