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Grades 6 and 7 Beginner About 15 min Version 1 Awaiting review Premium

What is soil made of? The soil jar test

Soil is not just one substance. It is a mixture of rock particles of different sizes (gravel, sand, silt and clay), humus made from rotting plants and animals, water and air. When soil is shaken with water and left to settle, the heaviest, largest particles sink first and the finest settle last, so the soil separates into layers. Humus is light, so it floats on top.

What you will learn

  • Name the main parts of soil.
  • Explain why soil particles settle in layers.
  • Compare the make-up of soils from different places.

Before you start

  • Know what sedimentation is. Try "Sedimentation and decantation" first.

Materials

  • Garden soil, river soil and clay soil
  • Water

Equipment

  • 3 tall jars with lids

Procedure

  1. Each jar holds water and a different soil sample: garden soil, river soil and clay soil.
  2. Shake (stir) each jar so the soil mixes with the water.
  3. Leave the jars still and use the timer until the layers form.
  4. Compare the thickness of each layer in the three jars.

How this simulation is simplified

  • Settling time is shortened. A real soil jar can take a day for the clay to settle.
  • Each layer is drawn with a thickness in proportion to the amount of that part in the soil.