Thursday, 3 September 2015

All about soil

Yesterday we talked about soil and how soil is made by weathering and erosion.
Teacher promised to bring a bag of soil to school today so we could do some tests on it.
We broke into groups and each group had a different task to do.
The yellow group used magnifying glasses and tweezers to investigate what exactly was in the soil sample.  We found roots, a dead snail, a worm, a stone, and bits of grass.
The red group used a garden sieve to break the soil into smaller pieces.  We also used magnifying glasses to see what was in the soil.  We found lots of little stones and a shell.

The green table investigated if soil sinks or floats.  We put soil into a bottle and added lots of water.  The soil and water were mixed together and then left to settle.  After a little while we could see the brown water becoming lighter in colour and we noticed that most of the soil sinks, but little pieces of soil, wood, roots and grass float.
(This is what it looked like after leaving it to settle all night...the water is much clearer now)
The white table and the blue tables had a bit of a competition.
Each table tried to make dirty water (water mixed with soil) clean again.
They did this using filters.
The white group used filters made from stones, sand and cotton wool (in that order, we hoped the stones would catch the biggest pieces of soil, the sand would catch the smaller pieces and the cotton wool would catch all the small pieces that were still left) to filter the water, while the blue group used just a coffee filter to filter the water.  We all had a guess before we started as to which filter would work better.  Here is what we guessed:
Which do you think will work better?
Here is the white group at work:
Here's the blue group with their coffee filter:
 The result:  The coffee filter worked better than our stone, sand and cotton wool filter.
We felt that this is because the stones we used might have been dirty themselves and so added to the dirt instead of filtering it away, and using sand was a bad idea because it ended up dripping into the bottle along with the dirty water.  We decided that if we use filters again we will only use cotton wool.  We think that a cotton wool filter might be great for cleaning water.
We learned lots about soil today, and we showed off our new-found knowledge when another 2nd class came to visit us and hear about our findings.

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