The italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included supporting the teacher’s understanding of the content being introduced within the CELL.

ANALYZE IT

Instruct students to complete the Analysis Questions in their SDRs then discuss them as a class. Use the suggested responses below to guide students’ answers.

• How was a watershed modeled in this Investigation? A watershed was modeled using a beaker filled with water to represent a stream or river. Water movement was simulated by stirring with a stir bar. Sediment in the water was modeled with flour.
• What is sediment? Sediment is made of particles of rock, soil, and other materials that are found in the water of a watershed. What is sedimentation? Sedimentation is the process by which sediment settles out of the water to the bottom of a watershed.
• How does the amount of sediment in the water relate to water velocity? As water velocity increases, more sediment is churned up from the bottom and is suspended in the water. Less sedimentation occurs at high water velocities.
• What is turbidity? Turbidity is the cloudiness of the water. How does the amount of sediment in the water relate to turbidity? The more sediment that is suspended in the water, the cloudier the water will be and the higher the turbidity will be.
• What is a spectrophotometer? A spectrophotometer is an instrument that measures the amount of light that passes through or is absorbed by a liquid.
• Why did you use a spectrophotometer in this Investigation? In this Investigation, a spectrophotometer was used to determine the turbidity of the water at different velocities. Turbidity was determined by measuring % Transmittance – the amount of light that passes through the water. Water with high turbidity has a lower percent transmittance.

GET FOCUSED

Instruct students to complete the Focus Question in their SDRs then discuss it as a class. Use the suggested response below to guide students’ answers.

• Why did you use a spectrophotometer in this Investigation? In this Investigation, a spectrophotometer was used to determine the turbidity of the water at different velocities. Turbidity was determined by measuring % Transmittance – the amount of light that passes through the water. Water with high turbidity has a lower percent transmittance.
• How does water velocity affect sedimentation and turbidity in a watershed? After completing this Investigation, students should understand that turbidity increases as water velocity increases. Conversely, sedimentation decreases as water velocity increases.