Look for: There is not any soil in the hydroponic system

2.B.2 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.

As different students share what they figured out about the inputs that are below the surface and whether these can be sources of food molecules, listen for students to share ideas such as:

• There is not any soil in the hydroponic system.
• When the hydroponic plant food was tested with food indicators, there were not any of the food molecules.
• Plain water does not contain food molecules.
• None of the inputs we looked at that are below the surface contain food molecules.

When the class is explaining what they have figured out so far and the evidence they have to support this, some students might suggest that pieces of the food molecules might be in the inputs we looked at even if whole food molecules are not found in the inputs. This is great thinking! Suggest it sounds like we still have more to investigate, and encourage the class to focus on what we have figured out for the current discussion.

Project slide S. In their notebooks, students should draw a three-box Progress Tracker to help the class come to an agreement about the evidence and what the class has figured out in words and pictures. First, have students write down the question they have been trying to answer, Were any of the below the surface inputs sources of food molecules? Ask students what evidence they have been working with to answer this question (e.g., the set up of the hydroponic plant system, the hydroponic plant food, water, etc.).✱ Give students an opportunity to generate a list of ideas they have figured out now.