Mystery Powders Day 3

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SWBAT determine the contents of the mystery powder using their observations and testing chart.

Big Idea

Students test the "Mystery Powder" by dropping various liquids and then determine what's in it using their data and comparison skills.

Reigning in the Excitement

5 minutes

Focus First: Today is the day that the Mystery Powder will be revealed. Students have seen what reactions happen using the grape juice, vinegar, and how their white powders look after water has been added and evaporated. Today, we were anxious to get going. I could feel the excitement and energy and knew I needed to reign it in. So, I gathered them around in the classroom before going into the lab, holding the mystery powder jar up in my hand. Their eyes were focused right on the jar as I talked.

I started by explaining that we have come so far in being able to describe using precise language. I told them that I have seen great improvement! Words like "fizzing", purple, lumpy and spongy were noted and I commended their reaching out for excellent precise vocabulary! Praising them is a positive reinforcement strategy so they continue to be interested in using language skills well, since it is a weak area for most of my students.

I prepared them for today's lab by explaining exactly that the "Mystery Powder" contains two of the powders and is a "mixture." I explained that we needed to perform the iodine test and that I would bring the iodine to them rather than the "Gophers" getting it for the team. I explained that iodine is to be handled very carefully and that goggles must be worn. 

I told them that we would proceed in the lab and that after the iodine test, I would guide them with the last steps of our investigation.

Iodine Test

15 minutes

Using their testing sheets and Observation Chart, students followed my directions by placing pinches of each powder as we had the during the last two days of the investigation. When each group was ready, I brought a small medicine cup of the iodine solution to their table. I explained that they needed to be very careful not to get it on their clothes or on their skin. The iodine was the colorless type, but I explained that it still would stain their clothing. They were to drop two drops as they had done before on each powder and record their precise observations. I noticed that this testing sheet lends to cross contamination and therefore, different groups were going to have different reactions. If any of the cornstarch got into anything else, it would produce a yellow color. My reflection addresses why I chose not to focus on this issue.

It didn't take very long to finish up the iodine test and students were ready to find out what the Mystery Powder was!

The "Mystery Powder"

20 minutes

After I approved the iodine tests as being successful, the "Gophers" were allowed to get their "Mystery Powder" jars and begin their testing. I again filled little medicine cups with the iodine and held onto them until all other tests were performed.

Students took turns placing pinches of Mystery Powder in the proper places on their testing charts just as they had on the first day of the investigation. Then, they dropped the indicator (grape juice), water, and vinegar as they recorded their observations. When those steps were finished and all of their observation charts were complete, I brought them the small medicine cup of iodine.

It was fun to hear their thinking as about what they were seeing happen as the contents of the Mystery Powder was being revealed. Soon, everyone was finished and all of the observation sheets were complete. It was time for them to spend writing about the results independently.

What Have You Learned?

10 minutes

I passed out the Mystery Powder Assessment and asked students to quietly read the writing prompts to themselves. When they were finished I would visit them if they had a question about their writing expectations. I wanted this all done independently so that I could assess their thinking about this investigation and get a base line of how well they could infer independently about the whole experience. So, no collaborative discussion about their observation chart was allowed.

They wrote for the remainder of the class. I assigned it as homework. I explained that tomorrow we would gather and discuss our findings together.