This term for Science we have been looking at a variety of soil samples and analysing their properties and characteristics. Our latest experiment involved us collecting a soil sample from any location and placing it in a clear jar. Next we had to fill our jars with water and shake the jar so that all the water mixed with the soil. We then left the jars on a shelf in the classroom for 2 weeks so they could settle.
Check out some of our jars of soil …
We also placed a sample of the soil in a zip lock bag. This soil was kept dry at all times and placed next to our jars.
Our task was then to draw our jars of soil by firstly measuring the height of the jar and then the height of each different layer that we could see in jar. We then discussed as a class what soil type each layer would be. We discovered that the larger particles would settle to the bottom first as they are the heaviest. The very fine particles would be sitting on the top layer and then any bark or leaves float up the top. Here is the order of the layers and what soil type they would be:
Sand layer: These particles are the biggest and weigh more than silt so the bottom layer will be the sand part of the soil and pebbles will also be at the bottom.
Silt layer: Silt particles are smaller than sand and weigh less so they appear over the sand.
Clay layer: Clay particles are the smallest and will be on top. If our soil was really thick clay then there would be sticky lumps of clay at the bottom of the jar. Some of us had no clay or very small amounts which made it difficult to visually see in our jars.
Organic Material: pieces or leaves, bark and other material that has not fully rotted.
The water was very discoloured. This colouring was likely to be rotted plant (organic) material that has dissolved in the water.
This activity taught us that soil is made up of a mixture of sand, silt, clay and organic material and that different soil types have different amounts of each in them.
We also calculated the percentage of each soil type that we found in our jar. To do this we divided the height of each soil type by the height of the jar.
Finally we compared our soil in the jar with the same soil that was in our zip-locked bags. The focus questions we answered were:
- What is similar about your soils?
- What is different about your soils?
- What kinds of things are soils made of?
- Why are there different sized pieces in the soil?
All our data, drawings and reflections were placed on a poster and are now displayed in the classroom.
Our next task will be to study some rock samples!!!