1. Activity #28- Signs of a Chemical Reaction

2. Chemical Reactions
Occur when new substances are formed by changing the way in which atoms are arranged.
REACTANTS= substances used in a chemical reaction
PRODUCTS= substances formed by chemical reaction

3. Atoms in a Chemical Reaction

4. 6 Signs of a Chemical Reaction
Color Change
Formation of a Gas
Endothermic Reaction
Exothermic Reaction
Formation of a Precipitate
Odor Change

5. Sign #1: Color Change
Reactants: Cabbage Juice and Vinegar; Cabbage Juice and Baking Soda
Add 10 mL of cabbage juice to 2 test tubes
Add 3 drops of vinegar to one test tube
Add one lab scoop of baking soda to another

6. 6 Signs of a Chemical Reaction!
COLOR CHANGE
Substances change color
Color change is a product of two or more reactants
Examples: Rust, leaves changing color, mold

7. Sign #2: Formation of a Gas
Reactants: Baking Soda and Vinegar (Acetic Acid)
10 mL of Vinegar in test tube
1 lab scoop of baking soda

8. 6 Signs of a Chemical Reaction!
FORMATION OF A GAS
Bubbles often appear
Fizzes
A product gas is leaving the reaction mixture
Examples: vinegar + baking soda = carbon dioxide

9. Sign #3: Endothermic Reaction
Reactants: Citric Acid and Baking Soda
10 mL Citric acid in test tube
Take temperature
Combine w/ 1 lab scoop of baking soda
Swirl and observe temperature!

10. 6 Signs of a Chemical Reaction!
ENDOTHERMIC REACTION (temperature/energy change)
Chemical bonds break
Energy (heat) is absorbed from surroundings
Substance seems cooler
Examples: baking, cold packs, photosynthesis

11. Sign #4: Exothermic Reaction
Reactants: Hydrogen Peroxide and Yeast
10 mL Hydrogen Peroxide in test tube
Take temperature
Combine w/ 1 lab scoop of yeast
Swirl and observe temperature!

12. 6 Signs of a Chemical Reaction!
EXOTHERMIC REACTION (temperature/energy change)
Chemical bonds are made
Energy (heat) is released to surroundings
Substance seems warmer
Examples: fireworks, explosions, hand warmers

13. Sign #5: Formation of a Precipitate
Reactants: Ammonia and dissolved Epsom Salt

14. 6 Signs of a Chemical Reaction!
A PRECIPITATE IS FORMED
A solid that forms when two liquids combine
The solid particles are the product
Examples: Kidney stones, pearls, cheese

15. 6 Signs of a Chemical Reaction!
6. ODOR CHANGE
Produces new smells as the reaction occurs
Examples: Rotting, bad breath, body odor