Classifying Reactions Safety Reminder: Wear safety glasses and use ammonia in a well-ventilated area. Day 1 Materials: Part I: steel wool tweezers vinegar small jar or drinking glass water small bowl Part II: hydrogen peroxide small pieces of raw potato (yeast or beef liver may be substituted for the potato) small bowl Procedures: Part I: Reaction between iron and oxygen 1. Break off a small piece of steel wool and soak it in vinegar for at least one minute. Use tweezers to push the steel wool around to remove all bubbles. 2. Using the tweezers, lift the steel wool out of the vinegar and shake if gently over a paper towel. 3. Stretch the steel wool out and gently push it into the bottom of a baby jar. 4. Add water to a small bowl until the water is approximately three-quarters of an inch deep. 5. Invert the baby food jar and place it in the bowl of water. 6. At this point no water should be in the baby jar. You have essentially trapped a baby food jar full of air in the water-filled bowl. 7. Allow to stand for 20 minutes and then record your observations. 8. While the mixture is standing, complete Part II of the lab. Be sure to record your observations for Part I after 20 minutes. Part II: Decomposition of hydrogen peroxide 1. Pour one third of a cup of hydrogen peroxide into a small bowl. 2. Cut up several small pieces of raw potato and place them in the hydrogen peroxide. 3. Record your observations. Observations: Part I: Reaction between iron and oxygen Appearance of steel wool after 20 minutes _____________________________________ Part II: Decomposition of hydrogen peroxide Appearance of potato and hydrogen peroxide combination ________________________ Day 2 Materials: Part III: a penny dated after 1983 metal file or coarse sandpaper vinegar (CH3COOH) Part IV: baking soda (NaHCO3) vinegar (CH3COOH) cup spoon Procedures: Part III: Reaction between zinc and acetic acid 1. Use a file or sandpaper to completely remove the copper from the edge of a penny. Once the copper is removed you can see the silvery zinc that composes the core of the penny. 2. Place the penny into a small jar of vinegar so that the penny sits upright. This will allow the hydrogen gas to readily escape and increase the rate of reaction. 3. Allow the container to stand undisturbed for 30 minutes. 4. While the mixture is standing, complete Part IV of the lab. Be sure to record your observations for Part III after 30 minutes. Part IV: Reaction between baking soda and vinegar 1. Fill a medium-size cup with a couple of ounces of vinegar. 2. Add a spoonful of baking soda to the vinegar. 3. Record your observations. Observations: Part III: Reaction between zinc and acetic acid Appearance of penny in vinegar after 30 minutes ___________________________ Part IV: Reaction between baking soda and vinegar Description of what happened when the baking soda and vinegar were combined _________________________________________________________________ Questions and conclusions: Part I: Reaction between iron and oxygen 1. Write a balanced equation for the reaction between iron and oxygen. 2. Classify the reaction that occurred between the iron and oxygen. Apply this reaction to a real-world situation. Part II: Decomposition of hydrogen peroxide 1. Write the balanced equation for the breakdown of hydrogen peroxide. 2. What evidence was there that a reaction was taking place? 3. Write a balanced equation for another decomposition reaction. Part III: Reaction between zinc and acetic acid 1. Write the balanced equation for the reaction between zinc and acetic acid. 2. Classify the reaction between zinc and acetic acid and explain, in general terms, what happens during this type of reaction. 3. Give an example of a type of element and a type of compound that are likely to participate in this type of reaction. Part IV: Reaction between baking soda and vinegar 1. Two types of reaction occur when baking soda and vinegar combine. The first is a double replacement reaction. Write a balanced equation for this reaction. 2. What type do you think the second reaction is? Why?