1. Activity #34- Signs of a Chemical Reaction

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

3. 6 Signs of a Chemical Reaction 1. Color Change 2. Formation of a Gas 3. Endothermic Reaction 4. Exothermic Reaction 5. Formation of a Precipitate 6. Odor Change

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

5. 6 Signs of a Chemical Reaction! COLOR CHANGE Substances change color Substances change color Color change is a product of two or more reactants Color change is a product of two or more reactants Examples: Rust, leaves changing color, mold Examples: Rust, leaves changing color, mold

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

7. 6 Signs of a Chemical Reaction! FORMATION OF A GAS Bubbles often appear Bubbles often appear Fizzes Fizzes A product gas is leaving the reaction mixture A product gas is leaving the reaction mixture Examples: vinegar + baking soda = carbon dioxide Examples: vinegar + baking soda = carbon dioxide

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

9. 6 Signs of a Chemical Reaction! ENDOTHERMIC REACTION (temperature/energy change) Chemical bonds break Chemical bonds break Energy (heat) is absorbed from surroundings Energy (heat) is absorbed from surroundings Substance seems cooler Substance seems cooler Examples: baking, cold packs, photosynthesis Examples: baking, cold packs, photosynthesis

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

11. 6 Signs of a Chemical Reaction! EXOTHERMIC REACTION (temperature/energy change) Chemical bonds are made Chemical bonds are made Energy (heat) is released to surroundings Energy (heat) is released to surroundings Substance seems warmer Substance seems warmer Examples: fireworks, explosions, hand warmers Examples: fireworks, explosions, hand warmers

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

13. 6 Signs of a Chemical Reaction! A PRECIPITATE IS FORMED A solid that forms when two liquids combine A solid that forms when two liquids combine The solid particles are the product The solid particles are the product Examples: Kidney stones, pearls, cheese Examples: Kidney stones, pearls, cheese

14. 6 Signs of a Chemical Reaction! 6. ODOR CHANGE Produces new smells as the reaction occurs Produces new smells as the reaction occurs Examples: Rotting, bad breath, body odor Examples: Rotting, bad breath, body odor