Engaging the Student (Entry Task) 

Checking for Understanding (exit ticket)

1 class period 

• Student Instructions and Data Sheet

View the full lesson plan here:

• Lesson 6-4: Evidence for Chlorine Treatment Lab

Supplemental Article on how Chlorine added to water kills bacteria:

• Scientific American Chlorine Article 

In this lab, students will ask the question "What effect does the concentration of chlorine have on organic molecules?". Students use food coloring (an organic molecule) to model bacteria (an organic organism). 

• SE2000 Electrochlorinator as a source of chlorine
• Student Instructions and Data Sheet (1 per group) 
• Stock solution of blue food color
• 100 ml beaker
• Colorimeter
• Laptop
• Cuvette
• Pipette
• Timer 

Have students write a conclusion for their experiment that answers the investigative question.

• What were the Big Ideas (important concepts) from this investigation? 
• Include supporting data from your data table to support each of your big ideas.
• Explain how these data support your claim.
• Provide a scientific explanation for the data you collected.