This lesson is designed to connect to the following NGSS and Common Core Standards:
MS-ESS3-3 Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.
MS-ETS1-1 Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
Science and Engineering Practices:
Developing and Using Models (SP2):
Stability and Change: For both designed and natural systems, conditions that affect stability and factors that control rates of change are critical elements to consider and understand.
I begin every class by asking the students, "What are you going to learn today?" Students respond by referring to the Essential Question, "How can we interpret data about how human activities affect Earth’s systems in order to develop technologies to monitor and minimize the effects?". This EQ is included on their Unit Plan and on the front board.
As the previous lessons helped develop their understanding of the skills in the Unit Plan, I ask students to reevaluate their self assessments from the previous day. Students rank themselves on each of the skills included in the Unit Plan. Students rank themselves on a scale of 1 to 4 (4 being mastery). Students will continue to update these scores over the course of the unit. I emphasize to them that it is ok not to be at a "4". Learning is about growth! We will use this starting point to track the growth in their learning.
Notice in the student work below, that the student updates his scores over the course of the unit as he grows in his level of mastery.
To begin, I ask students to brainstorm at tables what engineers may have to consider when designing a solution to a problem. I remind students that engineers are always working with constraints, or rules/guidelines that must be followed.
After brainstorming, through discussion we develop a list that typically includes the following:
I say something like, "Wait...you mean that engineers don't just get to make whatever they want?" Students explain how these factors limit the solutions that engineers actually can take into production.
Then, I say, "All new technologies have benefits, limitation, and short and long term consequences. Engineers have to consider all of these when determining the effectiveness of a new technology. Today, you are going to evaluate a couple of solutions that scientists and engineers have developed to aid in purifying polluted drinking water. It will be your job to identify the benefits, limitation, and short and long term consequences of each of these technologies."
In the first lab station, students take sludge water that I create through a series of reactions that result in water that the students can actually see through. The picture above shows the sludge water on the right and each step of the process down the line. The Desalination and Water Purification Lab document includes the procedure for this experiment.
It really is amazing how easily we can make a difference in the clarity of the water!
While the procedure is in the lab document, there are a few things you will need to complete this lab:
1. The sludge water I create is just water, dirt, food coloring, salt, sugar....basically just make it unclean with what you have access to!
2. You will make a mini biosand filter. This is just a cup with holes that has layers of sand and gravel in it. If may seem counter-intuitive to students to think, "I want to clean my water, let's run it through dirt.", but dirt provides an awesome filter!
3. Lime (Calcium Oxide) and Alum - Both of these can easily be ordered through any science material supplier. In addition, Alum can be found with the spices aisle at your local grocer.
This student notes that the advantage of this technology is that it does clean the water and is cheap. However, she notes that it doesn't clean every dissolved particle out, only a small amount of the original water is collected at the end, and that adding chemicals could cause consequences down the road.
In this lab, students place salt water in a flask with a stopper and connect a tube to the flask and a beaker in a bucket of ice to go through the desalination process. Make sure students wear goggles and heat resistant gloves. (I actually tell students that I am the only one that can take the flask off the burner when they are finished. The flask and beaker get really hot!)
Another safety tip -- as soon as the burner is turned off, remove the tubing from the beaker. If you don't, the pressure will change quickly and actually suck your newly cleaned water back into the flask! This motion of water happens quickly and can result in the flask falling over. I make sure that I hold up the beaker so that students can see the clean water that transferred into the beaker from the flask. The actual procedure for this lab is included in the Desalination and Water Purification Lab Student Document.
While the procedure is in the lab document, there are many components to the set up. The video below gives you a closer look at those materials.
This student notes that desalination is useful because there is a limited amount of fresh water in the world, some of which is polluted. So, desalination could help us produce drinkable water if there were a shortage. She also explains that it is a long and costly process and notes that taking salt water from the ocean could take away habitats from fish.
After we use desalination and water treatment to clean water, I have a Ford Motor Company environmental engineer come in and present to my students about how Ford treats waste water that is created when producing a car. I have the engineer address how Ford works to conserve water and how they evaluate the advantages, limitations, and short and long term consequences of the technologies that they produce. This provides my students with a great opportunity to close this lesson with a real world applicatin.
The picture below is actual waste water that the engineer brought from a Ford plant. The engineer takes the water through the treatment in front of my students. Here, the solid particles suspended in the waste water are coagulating. So cool!