Chemical Tests
Lesson 9
Testing Unknown Solids with Red Cabbage Juice
In lessons 3-10 students perform a series of tests to help them determine the physical and chemical properties of the five unknown chemicals.
3. Lesson set up and Management
GLE 1.1.1 Understand how to use properties to sort natural and manufactured materials and objects.
GLE 2.1.1 Understand how to ask questions about objects, organisms and events in the environment.
(3) Recognize the question being answered in an investigation.
GLE 2.1.2 Understand how to plan and conduct simple investigations following all safety rules.
(345) Follow all safety rules during investigations.
(345) Identify and use simple equipment and tools to gather data and extend the senses.
GLE 2.1.5 Understand how to report investigations and explanations of objects, events, systems and processes.
(3) Report observations of simple investigations without making inferences.
Easily included:
GLE 2.2.1 Understand that all scientific observations should be reported accurately and honestly even when the observations contradict expectations.
(3) Explain how scientific observations are recorded accurately and honestly.
(3) Explain why scientific records of observation are not changed even when the records do not match initials expectations.
GLE 2.2.4 Understand how to make the results of scientific investigations reliable.
- Students predict, investigate and record their results for what happens when a few drops of cabbage juice are added to each unknown chemical.
3. Lesson set up and Management
Materials:
- Use the "Check Your Science Pail" poster board for quick student reference. Add "hand lens" and "black paper."
- Signs with each material and the amount needed to be picked up at the materials center are helpful.
- If your cabbage juice is green, add vinegar to it a drop at a time until it is blue-purple.
- If your cabbage juice is pink, add baking soda, a pinch at a time until it is blue-purple.
- Test your cabbage juice before the lesson with baking soda (blue unknown) and alum (yellow unknown) to make sure it is working properly. The Baking soda should turn green and the alum should turn a darker/brighter purple. If it is not working properly, you will need to make a fresh batch following the directions in the manual or request a fresh batch from your district materials center.
Student Management:
- Assign one partner to be the materials manager and have that student pick up the materials from the materials center after you model how to do it.
- PROCEDURE #2
- It is helpful for visual learners to allow them to use a crayon to highlight each color word to make recording observations even easier. Show students the overhead and model what section they will be using and how to color code it.
- PROCEDURE #4
- As students are recording their own observations on their tables, carry a record sheet around, listen to their discussions, look at their written observations and record ideas from each group for class discussion during Procedure #6.
Sample student work from Lesson 9
- PROCEDURE #6
- Refer to the information you collected from the groups, telling the students you gathered these from groups as they were working. Share their ideas to enhance class discussion. Many students that hesitate to share ideas out loud feel valued when they hear one of their ideas. This leads to more participation. Even though the ideas are student generated, gathering ideas as they work allows you to do quality control and focus on strong scientific observation words.
- Use a laminate chart to record class results for red cabbage testing. It is helpful to make this chart at the beginning of the unit and have it displayed with all other test result charts.
- ASSESSMENT
- There are so many assessment ideas you are asked to focus on. Narrow your focus down to two or three specific concepts. Have student write in their science notebooks for assessment.
Writing Support:
- Students will record their predictions and observations during the red cabbage juice testing. They will also:
- Respond in their science notebooks to what they now know about each unknown that they didn’t know before
- Compare and contrast the unknown chemicals.
- Write about any chemicals that stand out during cabbage testing.
Reading Support:
- The extension activities suggest reading the book The Legend of the Indian Paintbrush by Tomie DePaola because the book tells about how plant juices are used for painting.
- The PBS website Zoom Games Kitchen Chemistry
http://pbskids.org/zoom/games/kitchenchemistry/ is a great opportunity for kids to read and complete a kitchen mystery scenario. Kids are taken through the inquiry process as they work to collect clues using their knowledge of chemistry. It is most popular with my third graders. Use later in the unit.
Math Support:
- Have students time the 15 seconds after adding the cabbage juice using the clock instead of counting.
- When sharing with the students the approximate time they will have for the activity, list the start time on the board and have them practice elapsed time by providing the approximate stop time for you to list under start time.