I A  Pour 1 spoonful of bb's through a stationary funnel onto a 3x5 index card. B Repeat, forming a mound on a separate 3x5 index card for each soil. C Trace the perimeter of each mound on each card, and write the material name on the card. D Measure the height of the mound. E Position a 3x5 index card and insert quickly to dissect the mound. F Use a different colored pencil to trace the outline of each mound.` *For more advanced students, use same measured quantity, either mass or volume.. Observe:  Are all mounds the same shape?  Record: Write your observations and summarize the results. Discussion points: Soil particles are held together by cohesion, the attraction of like forces, and friction.  All particles will seek the lowest possible energy state (the bb's will not form a mound, but a layer only one thick).  The finer particles have more cohesion because they have more surface area and more friction since the edges are not smooth and round.  See "Why there are no dry sand castles" *For more advanced observations, examine each particle type under a microscope to identify their shape.  This should enhance the discussion on surface area and friction. Follow-up activities for older students: I G  Use a protractor to measure the angle the mounds formed with the table as traced on the 3x5 card. H Use a ruler to measure the width of the mound (diameter) from the perimeter trace. I Calculate the width to height ratio. J Calculate the area of the base. K Estimate the volume of the mound. Compare:  Do all soils have the same width to height ratio?  Do all soils form the same angle with the table?  Record: Write your observations and summarize the results.

Part 2. Wet soils Materials:     3 oz cup or other small container     tray or oblong pan to hold the castles, sand and water     play sand     squeeze bottle (or other way to add water slowly) Hypothesis: Adding water to sand will not change the shape of the mound. Methods:
II	A	Place sand into pan or tray.
	B	Add water to the sand until it will form a ball.
	C	Use a 3 oz. cup to build a tower (sand castle).
	D	Then use a squeeze bottle to slowly add water to the center of the tower.
	E	Continue adding water and observe changes.
Observe:  What happens to the appearance (color or shine) and shape of the sand castle?  Record: Write your observations and summarize the results. Discussion points: Water adds the force of adhesion to the sand (an adhesive bandage might help demonstrate the point).  Water is held between sand particles and holds the particles together.  Wet sand will hold shape in a right angle.  But as more water is added, there is eventually enough water in the sand that the water layers will be too thick to hold the sand particles together and the tower will slump.  So a little water holds it together, but a lot of water will make it fall apart.  See "Water allows sand castles" and "How much is too much?"

Follow-up activities for older students:

II	F	Build more sand castles and add the water at different locations (middle, base, etc.)
	G	Measure the amount of water required to cause the castle to fail (slump).
Compare:  Do the castles fail in the same way when water is added in different locations?  Is the same amount of water required to achieve failure when added in different locations? Record: Write your observations and summarize the results. Follow this link to see some very elaborate sand "castles". Part 3: How much water is too much? Materials:     Different soils: sands, bentonite, silica flour, topsoil, etc.     Balance, graduated cylinders, or pipettes Hypothesis:All soils have the same saturation percentage.      (The saturation percentage of a soil is the amount of water required to cause a soil to begin to act like a liquid.) Methods:

III	A	Weigh 10 g of dry sand into a small beaker.  Use 1 tablespoon of soil if you do not have a balance.
	B	Add water about 1 ml at a time until the soil glistens slightly, will slump a little if turned on its side, and a cut through the center will close if the bottom is gently tapped against the desk a few times.
	C	Calculate the saturation percentage.                            saturation % = 100 (water added / dry soil weight)
	D	Repeat for other soils.
Observe:  Do all soil materials have the same saturation percentage?  Record: Write your observations and summarize the results. Discussion points:  The amount of water required to saturate a soil is determined by the particle size of the soil.  Finer soil particles have more surface area and require more water.  Clay minerals that swell when water is added require even more water to achieve saturation. Follow-up activities for older students:

III	E	Place the saturated soil into a small petri dish until it is level the top.
	F	Allow the soils to dry and observe any changes that occur.
	G	Measure the diameter of the petri dish.
	H	Measure the distance occupied by cracks along the diameter, or gently push the soil together and measure the distance between the edge of the soil and the dish along the diameter.
	I	Calculate the shrinkage.                          shrinkage % = 100 ( cracks distance / diameter of petri dish)
Observe:  Do all soils shrink and crack the same?  Record: Write your observations in the table. Discussion points:  The clay minerals with the greatest amount of shink-swell are in a group called smectites.  Two common types are montmorillonite and bentonite.  These clays are commonly used as drilling mud and clay liners for ponds and lagoons. Updated 06-30-2005. Copyright 2005. Clay Robinson, Ph.D., as to all resources: Materials may not be reproduced without Dr. Robinson's written consent. Students are prohibited from selling (or being paid for taking) notes or webpages during this course to or by any person or commercial firm without the express written permission of the developer of these pages.

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