LESSON: SOILS ARE FILTERS UNIT 4: Kilohonua & Kalawai (Geology & Hydrology)

Transcription

1 3 LESSON: SOILS ARE FILTERS UNIT 4: Kilohonua & Kalawai (Geology & Hydrology) Objectives: 1) To understand what soil is and why it is important; and 2) to learn basic concepts in chemistry and physics through experimentation. Time: Total 55+ min Procedures: 1. INTRO LECTURE & POWERPOINT: Explain what soil is and how soils form (link to rock cycle). Ask students why soil is important (e.g, nutrients to plants, physically & chemically filters our drinking water). Show different types of soil (e.g. clay, sand, topsoil, etc.). Preview vocabulary. View the Soils PowerPoint, Part 1. (See Teacher s Notes sections A & B). Another Soil PowerPoint you may prefer is an automatic download to your desktop (no webpage will open) at: 2. COLLECT & PROFILE SOILS: Read the 1 st paragraph of the handout aloud with the students (see Teacher s Notes, section C), then collect soil samples nearby (or you may use the samples you collected yourself above). Then do the simple analysis of soil conditions described in the handout, briefly following up in a later lesson once all materials have settled. 3. DEMO/LAB OR POWERPOINT: SPONGES Use a sponge to illustrate key soil concepts related to agriculture, water, the environment, and engineering. Students can follow along with the demo using their own sponges, water and basins. (See Teacher s Notes section D &/or the Soil PowerPoint, Part 2.) 4. ACTIVITY #1: LAB & TALKING POINTS Soil is a Filter (by Dr. Dirt. Students will discover that soils physically and chemically filter impurities out of water and the role of soil in having good drinking water. See Teacher s Notes section E and students Soil is a Filter handout. 5. SUMMARIZE KEY POINTS. End with the importance of soil in filtering Hawaii s drinking water. Preview next lesson: Is Hawaii s drinking water safe? Materials: For teacher: Soil samples (sand, topsoil); sponges; colander, sieve &/or screen; coffee filters; clear large containers for soil collection & analysis For students: 3oz and 5oz paper cups for each group; toothpicks; grape Kool-Ade; Safety: n/a Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 1

2 Assessment/Performance Indicators: Informal assessment: Active participation in lecture and activities. Formal assessment: none Points: 10 pts for full participation 9=B 8=C 7=D Exceeds Expectations: Student is able to explain how soil is linked to rock cycle Student is able to illustrate key soil concepts related to agriculture, water, the environment, and engineering Student can articulate importance of soil in filtering Hawaii s drinking water Learning Styles: Meets Expectations: Student can explain at least two ways soil is important Student can demonstrate how soil is a filter Student can explain key points of lesson Needs Improvement: Student can identify one way soil is important Student can identify soil as a filter Student turns in assignments, but work is not complete Left Brain Right Brain Auditory Visual Kinesthetic/Tactile Spatial Enrichment/Extension: Make Edible Soil Profiles : (fun but may be messy) This website has many other soil and science activities to try: Other Ohia Project Lessons: click on water lessons or go directly to: Keywords: agriculture, biochemical cycles, chemical filter, ecosystems, engineering, environment, humus, nutrients, organic matter, rocks, soil sedimentation test, soils References Information about soil water from sponges: Soil as a filter by Dr. Dirt: Moanalua Gardens Foundation, Cultural and Environmental Education in Hawaii Information for two activities: Soil is a Physical Filter (Ohia Project) and water lessons EARTH SCIENCE by David A. Katz. Information of the Earth s layers Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 2

3 Teacher s Notes for: Unit 4, Lesson Geology & Hydrology A) Vocabulary Nutrient nourishing substance Compound combination of chemicals Leachate - a solution or product obtained by leaching or percolation Cation (say KAT-eye-on) positively charged ion Anion (say AN-eye-on) a negatively charged ion B) Discussion Questions What types of rocks and/or soil do you see at home? Where do you see something different in Hawai i? Where do you see more greenery and what does that tell you? How is a rock like a sponge as a filter? How are rocks in Hawai i different from other places in the word? Similar? C) Collect & Profile Soil Samples Get permission to do this at school in the agriculture yard, a garden, the edge of a field or at a nearby stream or beach. You ll need shovels and buckets. D) Sponge Demo Discuss images below using sponges in class (also available in PowerPoint at end of Hawaiian Soils). Retrieved & adapted 5/08/08 from: A household sponge can be used to demonstrate several characteristics of the relations of soil and water. "Dry" Soils Infiltration and Runoff Wetting and Saturation Water Holding Capacity Percolation and Drainage Engineering and Bearing Capacity Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 3

4 COLLECT & PROFILE SOIL SAMPLES The ground is modified and enriched by the plants growing on it. Making a section of soil (figure 4), you can observe different layers: a layer rich in organic matter, the humus (O) a layer rich in roots and living organisms (A) a layer less rich in life, but still used by roots (B), and an inert soil (C). 1 - With a shovel, dig a hole of at least 40 cm (15inches) deep in a meadow. Describe the layers of soil which you see, perhaps take some pictures. 2 - Do the same in other kinds of soil, for example in a wood, or near a river. Make comparisons and try to explain the differences you observe. ANALYSIS OF THE SOIL COMPOSITION The soil is composed of many different sized particles. With this simple experiment you can separate the main components of the soil and evaluate their proportions. 1 - Go into a field an collect a sample of soil. Put it in a jar of water. Stir it well and let it settle. Observe and describe the different layers of materials. 2 - In water, particles settle more quickly the bigger they are. It is possible to use this property to determine the amount of each component of the soil. Put 3 parts water and 1 part of soil in the container (try 1 cup soil and three cups of water in a quart jar); shake the container for 5 minutes and let the material set. With reference to the figure 1, after 40 seconds measure the thickness of sediment. Call this A; after 30 minutes measure again and call this B; after 24 hours measure C. Now, by subtraction, you can determine the thickness of the main layers: C-B = layer of clay, B-A = layer of silt, A = layer of gravel and sand. Using a sieve with 2 mm holes (less than 1/8 inches), you can separate the gravel from the sand and determine their ratio. On the basis of these data, calculate the content (%) of each component of the soil sample. Retrieved & adapted 5/23/08 from: Repeat the same experiment with soil collected in other places (i.e: meadow, woods, stream bank) or anyplace the soil is different (i.e: muddy, sandy). Describe the composition of each soil and try to explain the differences. You can also evaluate the composition of the soil for a potted plant, and correct it. E.g, if water doesn't drain well, would more sand help? If it needs to hold water longer would clay or organic matter be helpful? Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 4

5 Activity #1 - Soil is a Filter (by Dr. Dirt) Retrieved & adapted 5/08/08 from: This series of film clips demonstrates the process and results with two soils: a sand and a clay loam. A clay loam is a fine-textured soil. This example also has about 2% soil organic matter, which makes the soil dark. Brief film clips are available in Quicktime (QT) or RealPlayer (RP) formats. If neither is available on your computer, click the name above to download them. Materials and Preparation: 3 oz and 5 oz solo cups (Put 3-5 holes in bottom of 5 oz cup. A toothpick works well.). The 5 oz cup fits inside 3 oz cup, then put the toothpick inside, between the cups. grape Kool-ade other colors, e.g., green, red, orange, yellow food coloring "floaties" clean sand fine topsoil Note: The results are more dramatic if the sand has been sieved to remove the smaller particles. If you do not have soil sieves, you can use a colander or a spaghetti strainer if the holes are small. Another material that makes a good sieve is screening. A fine screen attached to a small frame makes an excellent sieve. Introduction: Ask students What is a filter? (Show a coffee filter or a tea bag to aid discussion.) Can soil be a filter? Do all soils work the same? Hypothesis: Briefly explain Have students make hypothesis and complete table in Soil is a Filter handout. What will happen to the dirty water "floaties"? What color will come out the bottom? Methods: We will use two soils, a sand by itself, and a sand with topsoil on top. (The sand keeps the topsoil in the cup.) Sand has large, rough particles. Topsoil is a mixture of particle sizes. SAND: A. Take a 5 oz cup with holes in the bottom and fill it half full of sand. B. Put it inside the 3 oz cup. Put a toothpick between the cups so that air can escape from the bottom cup. C. Pour some of the dirty water into the top cup Ask Students What happens to the things floating in the water? A. Pour out the water in the bottom cup. B. Pour some of the grape Kool-aid into the top cup. Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 5

6 What color is the Kool-ade that goes into the cup? What color is the water that collects in the bottom cup? Direct students: Observe, share and record their observations on the handout. TOPSOIL: A. Put a layer of sand the width of your pointer finger in the bottom of the 5 oz cup. (It has holes in it.) B. Add topsoil until the cup is half full. C. Put the 5 oz cup into the 3 oz cup. D. Pour some of the grape Kool-ade into the top cup. Ask Students What color is the Kool-ade that goes into the cup? What color is the water that collects in the bottom cup? Is the water in the bottom cup the same color for both soils? Direct students: Observe, share and record their observations on the handout. The photo shows the results of a filtering exercise. The upside-down cup on the left shows the holes in the bottom. To the right of that is a cup with soil inside the smaller cup. The toothpick is barely visible between the cups on the right side. 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 soils vary in color from gray to red to brown to the light brown sand on the right. 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 coffee filter is given to the students to take home to remind them that soil is a filter. Talking Points cut out the following information on small paper slips and distribute among the class, asking each to state what their paper says and, if they can, how it relates to this lab. Direct students: Share and record their conclusions on the handout. Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 6

7 Name: 1. Lab: Soil is a Filter Class: HYPOTHESIS Dirty water Grape Kool-ade Sand Hypothesis (guess) Topsoil Hypothesis (guess) 2. EXPERIMENT Dirty water Grape Kool-ade Sand Observations Topsoil Observations 3. CONCLUSIONS Physics Chemistry Applications of this knowledge to your life Application of this knowledge to the community Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 7

8 Talking Points Activity: Soil is a Filter Cut out the following information on small paper slips and distribute among the class, asking each to state what their paper says and, if they can, how it relates to this lab. 1. Physics (how things work) is the reason the water flows faster through the sand than through the clay loam. 2. Chemistry (how things are made) is the reason the leachates are different colors. 3. The clay particles have a negative charge. 4. The organic matter has both negative and positive charges. 5. The organic dyes in grape drink have opposite charges: Blue is positive, red is negative. 6. Since opposites attract, the blue dye is attracted to the clay particles, while the red dye is allowed to pass through the soil. 7. Nitrates (and other soil chemical compounds) are anions (have negative charges), and so move through the soil with water. 8. Other compounds, like ammonium and potassium, are cations (have positive charges), and so tend to be held in the soil. 9. Blue and red make purple. 10. The smallest soil particles (clays) have a negative charge. 11. Opposite charges attract and like charges repel. 12. In all cases the red dye passes through the soil, so it must have a like charge as the soil (negative). 13. The blue dye is retained in three of the soils, so it must have an opposite charge (positive). 14. In this case, the soil with the purple leachate had very good structure, and the Kool-ade probably went through the pores and did not mix much with the soil. Ka Hana Imi Na auao A Science Careers Curriculum Resource Go to: 8