Students build on their understanding and feel for flow rates, as gained from the associated Faucet Flow Rate activity, to estimate the flow rate of a local river. The objective is to be able to relate laboratory experiment results to the environment. They use the U.S. Geological Survey website (http://waterdata.usgs.gov/nwis/rt) to determine the actual flow rate data for their river, and compare their estimates to the actual flow rate. For this activity to be successful, choose a nearby river and take a field trip or show a video so students gain a visual feel for the flow of the nearby river.

Students build a saltwater circuit, which is an electrical circuit that uses saltwater as part of the circuit. Students investigate the conductivity of saltwater, and develop an understanding of how the amount of salt in a solution impacts how much electrical current flows through the circuit. They learn about one real-world application of a saltwater circuit — as a desalination plant tool to test for the removal of salt from ocean water.

In this activity, students build a water filter with activated carbon, cotton and other materials to remove chocolate powder from water.

Students learn about contact stress and its applications in engineering. They are introduced to the concept of heavy loads, such as buildings, elephants, people and traffic, and learn how those heavy loads apply contact stress. Through the analysis of their own footprints, students determine their contact stress.

Prior to reaching households, water is exposed to a variety of treatments designed to render it fit for human consumption and use. One of the first treatment steps is the removal of suspended solids using chemical additives called flocculants. In this activity, students learn about two commonly used flocculants and clean water collected from a local pond or river. They experiment with flocculant, stirring and pH variables.

Students investigate what types of materials biodegrade in the soil, and learn what happens to their trash after they throw it away. The concepts of landfills and compost piles will be explained, and the students will have an opportunity to create their own miniature landfill in which the difference between organic and inorganic waste will become clear.