Earth science

Gilla:		Dela:

Video

Materials

• Soil
• 1 jar
• 1 spoon
• Water

Short explanation

In this demonstration, you have separated the soil by grain size, with the largest grains at the bottom. At the top, you may also have a layer of floating dead plant parts.

Long explanation

Soil, or earth, is defined as the solid particles on the surface of planet Earth that are so loose that they can be dug in. Soil arises from erosion and weathering of the bedrock and thus consists of grains of different types of rocks. These grains can have many different sizes and these sizes have special names. The largest is gravel, followed by sand, silt and clay.

When you stir all these grain sizes in the water, you then allow them to sink to the bottom (settle) in the order of the fastest sinker first. And then it's the large grains that sink the fastest, because they are the heaviest and Earth's gravitational force pulls them the hardest. So from the bottom of the jar you will have gravel, followed by sand, silt and clay. However, it's not guaranteed that all of these grain sizes were present in your soil, but try to identify the ones you had. Gravel is 2.0-63 mm (0.079-2.48 in) large grains, sand is 0.063-2.0 mm (0.0025-0.079 in) large grains, silt is 0.002-0.063 mm (0.000079-0.0025 in) large grains and clay is anything smaller than this.

However, soil rarely only contains rocks but also a lot of other things. There are bacteria, viruses, insects, dead plant parts, water, air and much more. You can see the air when you pour water into the jar - it rises like bubbles! You can probably also see dead plant parts floating at the surface. You may also notice that the water in the jar is brownish - this is probably due to water-soluble organic material.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• Test with another soil. What is the difference?
• What does the mixture look like after one hour, two hours, and so on?

Gilla:		Dela: