Soil Compaction and Vehicle Mobility

Overview

Students begin by taking core samples of candy bars with straws to model how scientists and engineers study soil before building roads and structures. They measure bulk density and water absorption of soil samples such as sand, topsoil, clay, and potting mix to estimate porosity, then model compaction with cloud dough made from flour and baby oil, including volume and density calculations. In an online activity, they design and drive a vehicle in the Create a Car game. In the final challenge, teams build a non-motorized vehicle from recycled materials, test it down a ramp on loose and compacted surfaces, refine it, and present their design choices. Phases run 40 minutes (engage), 60-80 (explore), 60-80 (explain), 40 (elaborate), and 90-120 (evaluate).

Lesson Objectives

• This lesson engages middle school students in understanding soil compaction as a human impact on Earth's systems, using a model-based approach with cloud dough, and culminating in an engineering design challenge focused on vehicle mobility. Students will be able to
• Define soil compaction in terms of bulk density, porosity, and permeability.
• Analyze how human activities contribute to soil compaction and its environmental consequences.
• Apply mathematical concepts to calculate soil properties and vehicle pressure.
• Design, build, and iteratively refine a vehicle to optimize its mobility across various "soil" conditions, evaluating solutions based on criteria and constraints.
• Construct explanations based on evidence regarding the relationship between soil properties and vehicle performance.