Prep: 1 hr | Activity: 1.75 hrs
Students will examine the phenomenon of plant growth by designing and carrying out an experiment to demonstrate that plants need air and water to grow. Water and air are the primary variables for investigation, but students may also decide to investigate the role of soil in plant growth.
Students design an experiment to test a single variable related to plant growth: air or water. The experiment must define the dependent, independent, and controlled variables. All experiments should run for approximately the same amount of time. Students may be assigned a variable to investigate
What materials are required for plants to grow?
PE 5-LS1-1. Support an argument that plants get the materials they need for growth chiefly from air and water.
Engage in Argument from Evidence
LS1.C: Organization for Matter and Energy Flow in Organisms
Energy and Matter
In case of accidents and to prevent stains on clothing, have students wear an apron or an oversize T-shirt over their clothes. When working with Aqua Vega or soluble fertilizer, students should wear safety goggles for eye protection.
When the investigation is complete, you can dispose of plant materials in the classroom trash.
Prior to beginning the investigation, premix the Aqua Vega hydroponic solution if a group wants to test the necessity of soil, and set up the hydroponic growing system. Place the rock wool in the growing cups. You may wish to place a measured amount of soil in cups prior to seed planting.
Data will vary depending on the variables selected by students.
Student data should demonstrate that water and air provide materials for plants to grow. The vacuum bags provide for the removal of air. After you seal the bag, a residual amount of oxygen and carbon dioxide may remain. Seeds may germinate but will not live. Potting soil provides initial moisture so again, seeds may germinate, but will not continue to grow once the initial moisture is used. Remind students that light is not a variable for consideration in this experiment. The hydroponic system takes soil out of consideration as a necessary material for plants to grow. Students may use the system, or hydroponics can be an enrichment or extension activity.
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