Monday, January 12, 2009

Creating an Erosion Model

The model I created for class this year was born of simple desperation. Last year when we ordered new supplies to replenish our STC kits, I forgot to order replacements for this kit. The erosion lessons have been inspired by the STC Land and Water Kit
If I would have had the materials the students would have created their own erosion models, but I didn't so they didn't.

The recipe for creating the soil is as follows:
1 part clay
2 parts gravel
2 parts humus
6 parts sand

You can use these ratios to help come up with a reasonably good soil for testing. You may want to experiment with it to see if it is the right mixture for your needs. I placed the mixture in a large critter cage that I had left over from various animals. Make sure your container is water proof before you start. Remember, when you add water to this mixture, it is going to become incredibly heavy. Think about where you put it before you add water, you may not be able to move it later. Also, make sure that the stand you put it on can handle the weight.

Now there are some things for you to consider. If you only teach one science class, you are ready to go, if you teach two or more classes you may want to think about how you will proceed.

Things to consider if you have more than one science class:
1. Is it absolutely necessary to show the experiment live?
2. Do you have access to a camera and tv/projector that is large enough to be used to view the experiment?
3. Do you know how to record video for playback?

I think there are only two options for doing this experiment with multiple classes: make a model for each class or record the experiment for playback. I have found from past experience the model will be too wet to do back to back experiments. The results for the second (third, etc...) experiment will not be as good as the first.

I used a webcam to stream the experiment using Ustream. I then recorded it using Ustream and put it on my class blog. This allowed me to revisit the assignment almost four weeks later when we actually got to the lesson.

Here is the Scientific Method document my students followed for our first experiment on erosion:

1) Identify the Problem- What will happen to the soil when water runs over it?
2) Background Knowledge- The students identify 3-5 things they know about water and erosion.
3.) Hypothesis- The students write what they think will happen.
4.) Research- We don't usually research our experiments, but we do talk about using research for the science fair projects they will do next year. I leave this here as a place holder.
5.) Experiment- I break this up into two subsections
A. Materials- soil, tank, bucket, water, scraper to level soil, coffee filter
B. Method- This is where I put the step by step instructions.
1. Prepare the soil by pushing it until it covers about 3/4's of the tank bottom. Leave room
for the water to have a place to run to.
2. Pour water onto soil
3. Collect a sample of the runoff.
4. Filter the runoff water and examine what is left in the filter.
6.) Conclusion
1. Identify if your hypothesis is correct.
2. Come up with two extensions to experiment.

An extension you can do with this experiment is to map out the path the water took. You can have your students hand draw the path or you can take a picture and allow the students to open it with paint and they can "paint" the path.

If you have any extensions or ideas, please leave them in the comments below and I will add them (and give you credit).

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