OpenSciEd Unit 7.4 · Lesson 02 · 2.B
Look for: There are no food molecules found in the hydr…
From Teacher Edition
Facilitation guidance from the lesson plan — what to notice in student thinking and how to respond while teaching.
Building towards
2.B.1 Engage in argument from evidence to support or refute possible inputs of where plants get their food molecules from, such as hydroponic plant food or soil.
What to look / listen for
In the two questions in Part 5 of Which food molecules are in the hydroponic plant food? students should be able to argue that:
There are no food molecules found in the hydroponic plant food solution using evidence from the investigation such as, “When the food indicator for carbohydrates was added to the hydroponic plant food, the color of the indicator did not change,” the example is for carbohydrates but this would work for any of the indicators.
The hydroponic plant food can not be the source of the food molecules we find in plants. The evidence they could use to support this argument could be something similar to, “Since the food indicator for carbohydrates didn’t change color when the hydroponic plant food was added to it, there are not any carbohydrate molecules in the hydroponic plant food. So the plant food can’t be the source of the food molecules”
What to do
If students argue they found evidence of food molecules in the hydroponic plant food solution sample they tested, it might be helpful to talk through with them how they conducted their investigation and ask them for the data they collected (no color change or a color change when the food indicator was added to the solution).
Compile class data. Present slide Q. When students are finished running their experiments, compile the class data. Draw a data table on the board, and whenever a group is finished, each student should come to the board and record his or her findings by putting “Y” (if there was a change) and an “N” (if there was no change) in an open box for the type of food molecule tested for. This way, each student can see how his or her individual sample contributed to the community’s interpretation. The hydroponic plant food solution should not have any food molecules inside and therefore none of the indicators should change color. See the example class data table.