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Soil Pellet (structure, density) (Laura Silverman)


               Laura Silverman, 7th grade Science, Mulholland Middle School

Principle(s) Illustrated

  1. That solids can change their structure
  2. That density is affected when liquid molecules fit into the space between solid molecules
  3. That heat affects molecular motion.


  • Structure of Matter
8.3. Each of the more than 100 elements of matter has distinct properties and a distinct atomic structure. All forms of matter are composed of one or more of the elements. As a basis for understanding this concept:

c. Students know atoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long-chain polymers.

d.    Students know the states of matter (solid, liquid, gas) depend on molecular motion.

e. Students know that in solids the atoms are closely locked in position and can only vibrate; in liquids the atoms and molecules are more loosely connected and can collide with and move past one another; and in gases the atoms and molecules are free to move independently, colliding frequently.

  • Density and Buoyancy

8.8. All objects experience a buoyant force when immersed in a fluid. As a basis for understanding this concept:

a. Students know density is mass per unit volume.

Questioning Script

Prior knowledge & experience:

Water can be absorbed by soil.

Root question:

How much will the pellet expand, it at all?

Target response:

That it will absorb all the water poured into a 100 mL container, thereby increasing its density.

The liquid water is interacting solid soil which changes the structure of the soil molecules, and slides into the open areas between the soil molecules.

Common Misconceptions:

That the soil will absorb water but not expand when water is added.

Photographs and Movies

soil before and after

YouTube Video

YouTube Video


Bodner Research, Categories of Solids:

Windows to the Universe, Density:

Garden Guides: