Author: Lucy Daniels and Albert Kaskel- Adaptations made to the lab for the seventh grade science curriculum

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1 Cindy Eskina Students at Piper Middle School practice scientific inquiry by incorporating steps from the scientific methods into various activities and experiments. Seventh graders will participate and complete a lab called the The Big RC Juice Lab by following the steps to the scientific method. This lesson also introduces acids and bases. Students love this experiment because of the dramatic change in the red cabbage when the chemicals are added to each test tube. It is always exciting to hear the wows and is this is cool from students. Author: Lucy Daniels and Albert Kaskel- Adaptations made to the lab for the seventh grade science curriculum Title: The Big RC (red cabbage) Juice Lab Subject Area(s): Life Science, Scientific Inquiry, Scientific Method, & Chemistry Grade(s): 7 th Grade Description of Lesson: When scientists are asked questions, they may not know the answers. They think of possible answers called hypotheses, and experiment to find the correct answers. Using the results of the experiment, they may need to form another hypothesis and test it. This way of solving a problem is called the scientific method. Students will determine if chemicals W, X, Y, and Z are acids or bases by testing with the red cabbage juice. Length of Lesson: two class periods, which are 50 minutes. Time is needed for each table to set up materials and clean up. Student Objectives: Students will predict whether or not red cabbage juice will remain red when chemicals are added to it. Students will test their predictions with an experiment. Students will observe what happens and record their observations. Student will draw conclusions based on their observations. Materials: For the teacher: Prepare red cabbage juice by boiling the outer leaves in a small amount of water. Do not add salt or other seasonings. Pour off the juice. (The cabbage can then be eaten.) Red cabbage juice should be refrigerated if kept overnight because it will ferment. It can be kept in the

2 refrigerator for two or three weeks. Flower petals can be used in place of red cabbage juice. Place a petal in each test tube. The petals will change color when treated with W, X, Y, and Z. Review safety rules with students when working with chemicals. Model the proper disposal of chemicals for the students. Chemical W- (Vinegar) Keep containers closed when not in use. Chemical X- ( Rubbing Alcohol) Chemical Y- ( Ammonia) Chemical Z- ( Baking Soda Solution) Prepare by dissolving 5 g baking soda in 95 ml distilled water. The liquid should be clear. Label cups for the chemicals W, X, Y, Z and RC. I always demonstrate the lab so students know the appropriate lab behavior, lab techniques, and classroom expectations. Remind students to rinse out test tubes so chemicals from the previous class do not contaminate their results. For each group: Four to five droppers labeled W, X,Y,Z, and RC. This will help students not to interchange the droppers that could contaminate their results. Five cups labeled W, X, Y, Z, and RC. 40 ml red cabbage juice Test tube holder 5 test tubes (medium size) Chemicals W, X,Y,Z, and RC. For the class: Aprons Safety glasses

3 Gloves (may be optional) Procedure: Step 1: In the space below, predict what will happen to the red cabbage juice when chemicals W, X, Y, and Z are added to it. Step 2: Label five test tubes 1,2,3,4, and 5. Step 3: Add 10 ml of red cabbage juice to each test tube. Step 4: Add 10 drops of chemical W to test tube 1. Step 5: Add 10 drops of chemical X to test tube 2. Step 6: Add 10 drops of chemical Y to test tube 3. Step 7: Add 10 drops of chemical Z to test tube 4. Step 8. Do not add anything to test tube 5. This is the control. The control is the part of an experiment that is not tested. Step 9: Data and Observation- record your observations in the data table. Data Table: Test Tube Substance Added Color 1 W 2 X 3 Y 4 Z

4 5 RC Step 10: Questions and Conclusions: Scientific Explanation: 1. (a) Was your predictions correct? (b) What part of the scientific method is predicting? 2. Do all chemicals have the same effect on red cabbage juice? 3. Why did you record the colors changes? 4. What steps in the scientific method did you use? 5. What is the purpose of the control in an experiment? 6. Why is hypothesis called an educated guess? 7. Was your experimenting a way of proving your hypothesis? 8. How did your hypothesis change after experimenting? Acids are substances that have a sour taste. Weak acids, such as citric acid in lemons and limes, or acetic acid in vinegars, are found naturally in the foods we eat. Even cola drinks are acids. Hydrochloric acid is in our bodies to help start

5 such natural processes as digestion and to fight germs and bacteria. Other acids are made by humans for industrial use. Very strong acids, such as sulphuric and nitric acids, corrode, or eat away, tough materials, including wood, rubber, and metal. Scientists measure the strength of acid on a ph scale. Pure water which has no acid content at all has a ph of 7. Red cabbage juice is an indictor that can be used for less cost than litmus paper. The results were the following from each test tube: chemical W added to test tube 1 turned red/pink, chemical X added to test tube 2 turned blue, chemical Y added to test tube 3 turned green, and chemical Z added to test tube 4 turned green. If the red cabbage juice turns red/pink, the substance is an acid. If the red cabbage juice turns blue, the substance is a base. The intensity of the color also shows if the acid or base is strong or weak. Assessment: Students will complete questions and data table for evaluation. Missouri Standards Addressed: Strand 7.1, Concept A. Scientific inquiry includes the ability of students to formulate a testable question and explanation, and to select appropriate investigative methods in order to obtain evidence relevant to the explanation. Kansas Standards Addressed: Standard 1: The student will develop the abilities to do scientific inquiry, be able to demonstrate how scientific inquiry is applied, and develop understandings about scientific inquiry. Benchmark 1: Demonstrate abilities necessary to do the processes of scientific inquiry Indicators: Identifies questions that can be answered through scientific investigations. Designs and conducts scientific investigations safely using appropriate tools, mathematics, technology, and techniques to gather, analyze, and interpret data. Identifies the relationship between evidence and logical conclusions. Communicates scientific procedures, results and explanations.