Yup. The ocean. Which is salt water. This opened up Pandora's box for questioning again.
Mrs. Brinza found that data of parts of the city of Chicago were hard to find, but finding elevation data of many cities was fairly easy. So we looked at some maps using color keys that show elevation, along with actual numbers to plot a path the water takes:
We were really interested in where the water goes...and we figured out that all the treated water in Chicago leads to the Chicago River, which flows to the Illinois River, then the Mississippi River. From there, it heads downwards to the Gulf of Mexico, which leads to the Atlantic Ocean.
Yup. The ocean. Which is salt water. This opened up Pandora's box for questioning again.
After a lengthy discussion, we agreed to figure out what happens to freshwater when it combines with salt water, find a way to clean salt water to possibly drink it, and then see if this process could be a viable drinking source for the world, since so much of the Earth is covered in salt water. Phew! What a quarter it's been...now we're off to figure out the second part of our Driving Question about our clean drinking water!
We figured that going to the Chicago River or getting someone to get us a video of the Chicago River flowing might tell us which way the water goes, but it wouldn't help explain how it actually gets flowing to start with.
While buckets of water would contain water, they wouldn't keep the water moving, because the walls would block the water from actually moving, so we built a physical model instead!
We figured out that Chicago's treated water goes into the Chicago River. But this got us thinking that we didn't know which way the water flowed--towards Lake Michigan or away from Lake Michigan? We decided we should figure out how water flows to better understand which direction this "semi-clean, yet still has dissolved stuff in it" water goes!
Here's our thinking on investigations we can do tomorrow!
After figuring out all processes that clean dirty water at the wastewater treatment facility, it was time to go back to the DQB to see if we could answer any question, and sure we di!
We then agreed that if we knew that London's and New York City's went into nearby rivers, we wanted to know where our water goes after it's treated at our local WWTF!
So we pulled out our online maps again...and looked for our local WWTF and found two--one up north and one south. These were approximately 7 and 10 miles away from our school. We zoomed in and definitely saw the big pools of water being treated, and both locations were near different branches of the Chicago River.
Once we saw this, we started thinking about Lake Michigan right near the river and many of us have seen how this river actually connects to the lake. This got us thinking, which way does the river flow? Into the Lake? Away from the Lake? We're only concerned because we know there is still some dissolved particles in the water that leaves the WWTF and we wonder where that stuff goes. We've also got all these questions about where our clean water comes from and regardless of how the water flows, we may have some issues with the cleanliness of both the river and the lake!
So we figured out that physically removing things from our water CAN'T be the only way, especially since getting out the dissolved solids would be nearly impossible with any kind of filter. So students suggested two things: bring in an expert and maybe find some videos that detail the process.
Mrs. Brinza couldn't get someone from the local wastewater treatment facility to come in on such short notice, but while she was presenting at the ISTA/ICTM conference, retired Alcott science teacher Mr. White was coming in to sub for her. He recently had visited the wastewater treatment facility in Denver while visiting his son (who happens to work at it). Mr. White was surely the expert on what goes on there, as his son just gave him a detailed tour last month. So while Mr. White doesn't work at one, his recent visit made him an expert in our eyes!
Our videos from NYC and London's facilities confirmed what Mr. White shared with us about Denver's facilities, and we came to an agreement on the following:
1. WWTFs first clean the water through a physical/mechanical process, using big tools and machinery to remove the BIG solid stuff (i.e. baby wipes, bricks, garbage, etc). This stuff is sent to the landfill.
2. Next, water is treated biologically. This means small microbes like bacteria are added to the dirty water to consume (yes, EAT) all the dissolved stuff. This produces organic waste that either floats or sinks in settling tanks, and special equipment collects this organic material. The water is getting cleaner! Sometimes this "sludge" is actually used as a fuel source for the WWTF.
3. Lastly, the water is treated chemically, usually with bleach. Bleach kills any remaining micro-organisms still in the water before it is dumped into a river (the East River in NYC and the Thames in London). On average 85-95% of the dissolved solids are removed before heading into a body of water. That seems like a lot, but we're concerned about what is still left in the water for us and also for the wildlife and plantlife that make these rivers their homes.
This got us thinking...where does the water that is treated here in Chicago end up?!?!?
We felt we figured out so much about what happens at the wastewater treatment facility that we decided to publicly post what we've figured out so far! Here's a look at our DQB for 5th grade!
And here's the other half for the other class!
We had a class discussion around what our next steps should be and unanimously agreed we should figure out what exactly the wastewater treatment facility does with all the dissolved stuff in the water (and liquids, too). We'll be looking at some videos and hopefully an expert on wastewater treatment plants can visit our classroom soon!
So the students were really thinking hard...and it caused us to change our model yet again, especially as we gained more evidence from combining two models we've established. We know how filters work, and we know how a substance dissolves.
So if water moves through any hole, in any filter, isn't that evidence to suggest that water, like citric acid (or any other substance we looked into) also is made of pieces, too? The only way it can go through something is if it's able to "break apart," and it also flows really easily, so it must be made of pieces, too. We also know that when a substance dissolves, it moves everywhere in a liquid, so if water wasn't made of pieces, with little tiny spaces in between the pieces, then it wouldn't go through and fit down to the bottom (or the sides), which we know it did from tasting everywhere from the cup!
We took these ideas to mathematically prove the substance isn't gone when it dissolves, and that water is made of pieces, or particles too small we can't see.
So this got us thinking...if there are things super small in the water, and filter holes aren't small enough to catch them, how do they really clean the water? This is getting us thinking about new questions that relate back to our Driving Question for the unit--Where does my clean water come from and where does it go once we make it dirty?
How can we model that to show what we've figured out?
We spent a lot of time discussing what our evidence told us--that the substances we put into the water were still there but just so small! We then put these ideas into action and attempted to model them, especially as we're trying to figure out how the wastewater treatment facility may even get these dissolved solids out!
We developed some initial models for the dissolvability phenomenon, and here are some examples of student thinking. We agreed to "zoom-in" on both the substance entering the water and the water, too, as we agreed that the substance was still there but we just couldn't see it.
We agreed on the following after various students presented:
1.The zoom-in of the substance should show it made of pieces or particles. These zoom-in particles should be obviously bigger than in the cup.
2. The zoom-in of the substance in the water should show the pieces smaller than they are in the cup, because a substance that dissolves gets smaller when it enters water. The cup of water should NOT show visible pieces of the substance unless it's in the zoom-in.
3. The total weight of the pieces outside of the water and inside the water should be the same, as our weight test showed that no weight was lost.
4. Each substance that enters the water should be represented in a different way since they are all different substances--for example, citric acid is different than salt, so if citric acid is colored yellow, we can't use yellow to also represent salt.
We worked through our thinking to establish a consensu smodel, and here's what we came up with!
While our microscope tests told us that there was still stuff in the water, it was hard to tell what was what in our samples. This got us thinking about isolating individual items that we knew went into the water, but that we weren't really sure if they were there (not even the microscope could reveal with the highest magnification). Students were convinced that this stuff was still there, so we agreed more tests should be done to prove stuff was in the water (and some of our water samples with isolated stuff in them looked like regular water).
Here's what we came up with:
1. Do a water level test--we noticed that the water level kept rising with the dirty water we made, so if the water level rose when we put just ONE thing in, it should rise, too, proving the substance is still there even if we can't see it.
2. Do a weight test--we know that each of the substances weighs something, so if we add it to water, then the water should increase in weight even if we don't see it.
3. Do a taste test--yes! you read that right! Some of the substances are safe to taste, so hopefully we can still taste it when it is in water!
4. Do an evaporation test--let the water + whatever we add to it sit out in our classroom and let the water evaporate. Hopefully if the water evaporates, then whatever is still in the water will stay behind!
We hit the ground running today! Here's a glimpse at a student notebook for how we organized our data collection based on the student tests they wanted to investigate.
We had a quick discussion at the end of class today thinking about what these new tests meant. While we were really certain our microscopes would give us the evidence we thought we were looking for, it seemed as if our zoom-ins didn't really tell us much. Tasting, weighing, marking the level, and hopefully evaporating the water will give us a better picture of what happens when things enter our water. It'll hopefully also help us better understand how they get this stuff out!
So after all our investigation ideas came forth, we decided to begin using microscopes to see if they could tell us what was in the water. We set up our own slides using various water samples. There was a big discussion around NOT just using the dirty water, but using samples of each item we put in with water for comparison sake.
After using the microscopes, we figured out the following:
1. That's there's still stuff in the dirty water!
2. This stuff is REALLY small.
3. We can't tell what this stuff is so maybe we should do more tests.
Back to the drawing board on Tuesday!