Chemical Tests
Lesson 8
Testing Unknown Solids with Iodine
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 iodine 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.
- Iodine bottles should be prepared right before the lesson because iodine can lose its indicator properties over time.
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.
- Review safety rules carefully with students because iodine can stain clothing and is harmful if ingested.
- PROCEDURE #4
- Use a laminate chart to record class results for iodine testing. It is helpful to make this chart at the beginning of the unit and have it displayed with all other test result charts.
- It is helpful to show students a transparency pointing out exactly where they will be recording their information on Record Sheet 7-A.
- 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 Final Activities #1
Sample student work from Lesson 8
- FINAL ACTIVITIES #1
- 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.
Writing Support:
- Students will record their predictions and observations during the iodine testing. They will also respond in their science notebooks to what they have learned by adding iodine to the unknowns.
Math Support:
- Decide, as a class, how much time each iodine mixture should be stirred. Have students time the stirring using the clock.
- 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.