The smallest soil particles (clays) have a negative charge. Discussion points: Remember that blue and red make purple.The coffee filter is given to the students to take home to remind them that soil is a filter.The color of the water in the bottom cup ranges from purple (about the same color as the grape drink began), to bright pink, to almost colorless, to a murky red.The soils vary in color from gray to red to brown to the light brown sand on the right.The next four cups across the top contain the leachate (the water that ran through the soil) for the soils in the containers below them.The toothpick is barely visible between the cups on the right side. To the right of that is a cup with soil inside the smaller cup.The upside-down cup on the left shows the holes in the bottom.The photo shows the results of a filtering exercise.Is the water in the bottom cup the same color for both soils? Put a layer of sand the width of your pointer finger in the bottom of the 5 oz cup. What color is the water that collects in the bottom cup? What color is the Kool-aid that goes into the cup? Pour some of the grape Kool-aid into the top cup. What happens to the things floating in the water? Pour some of the dirty water into the top cup Put a toothpick between the cups so that air can escape from the bottom cup. Take a 5 oz cup with holes in the bottom and fill it half full of sand. (The sand keeps the topsoil in the cup.) Sand has large, rough particles. We will use two soils, a sand by itself, and a sand with topsoil on top. A fine screen attached to a small frame makes an excellent sieve. Another material that makes a good sieve is screening. ![]() ![]() If you do not have soil sieves, you can use a colander or a spaghetti strainer if the holes are small. The results are more dramatic if the play sand has been sieved to remove the smaller particles. other colors, e.g., green, red, orange, yellow food coloring.The 5 oz cup fits inside 3 oz cup, the put the toothpick inside, between the cups. 3 oz and 5 oz solo cups (Put 3-5 holes in bottom of 5 oz cup.
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