We've come back together after some time off and are moving forward trying to figure out what happens when various substances are in water.
From our microscope, boiling, evaporation, and weight tests, we have finally come to an agreement about what happens to some substances when they enter water. We think they dissolve, and that dissolving means the following:
1. A solid enters a liquid (such as salt into water).
2. Over time, the solid breaks down into smaller pieces.
3. These pieces are so small we can't see them with our naked eyes, but looking at the water and substance mixture under a microscope we see they are still there, just much smaller than before they went into the water.
4. None of the substance disappears! We can account for all the substance because we weighed it beforehand and after and it weighed the same.
5. The substance's small particles are spread out everywhere in the water, otherwise we would see it!
Our initial models to explain this looked like this:
From our microscope, boiling, evaporation, and weight tests, we have finally come to an agreement about what happens to some substances when they enter water. We think they dissolve, and that dissolving means the following:
1. A solid enters a liquid (such as salt into water).
2. Over time, the solid breaks down into smaller pieces.
3. These pieces are so small we can't see them with our naked eyes, but looking at the water and substance mixture under a microscope we see they are still there, just much smaller than before they went into the water.
4. None of the substance disappears! We can account for all the substance because we weighed it beforehand and after and it weighed the same.
5. The substance's small particles are spread out everywhere in the water, otherwise we would see it!
Our initial models to explain this looked like this:
As you can see, we didn't have agreement on what this looked like from a zoomed-in perspective. We had a deep discussion about what was really happening to the size of the pieces of the substance dissolving, and then we began to think more deeply about water.
In each student's models, everyone represented water as this whole piece. After using some play-doh, we began to see how a big piece of play-doh doesn't behave like liquid play-doh. However, by breaking the play-doh up into small pieces, it began to behave like the water in the cup! This helped support our ideas behind solids being made of particles, and since solids can become liquids, liquids must be made of particles, too!
In each student's models, everyone represented water as this whole piece. After using some play-doh, we began to see how a big piece of play-doh doesn't behave like liquid play-doh. However, by breaking the play-doh up into small pieces, it began to behave like the water in the cup! This helped support our ideas behind solids being made of particles, and since solids can become liquids, liquids must be made of particles, too!
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Water being made of particles also got us thinking about how water ALWAYS passed through any of the filters we used when we attempted to clean dirty water ourselves. Since all those filters had holes, and some of the holes were really tiny, we're thinking that water's particles must be smaller than any of the microscopic holes in the filters we used.
| All the water particles we made from play-doh were different sizes, and when we tried to demonstrate how they pass through a filter, we also came to an agreement: Since all water passes through a filter's holes that are bigger than the water particles, all water particles must be uniform, or the same size! Otherwise, some water would get stuck and other water would pass through. |
Our next steps: Now that we've figured out about how dirty water can contain liquids and other dissolved solids, how on earth does the wastewater treatment facility get out those particles?
Filtering them didn't seem to work! Is there another part of the cleaning process we don't know about?
Filtering them didn't seem to work! Is there another part of the cleaning process we don't know about?