Lab: Groundwater. Prediction: Which sample (4mm, 7mm, 12mm) will have the greatest porosity?

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1 Name: Date: Lab: Groundwater PART 1: POROSITY Purpose: To explain the relationship between particle size and porosity. Background: The porosity of a material is a measurement of how much of its volume is open spaces (also called pore space). is usually expressed as a percentage of the material s total volume. is important to anyone who works with ground water. Hypothesis: Materials: 1 paper cup, graduated cylinder, 4mm, 7mm and 12mm beads Prediction: Which sample (4mm, 7mm, 12mm) will have the greatest porosity? Procedure: 1. Pour 100 ml of water into your cup and draw a line where the water comes up to. Write 100 ml in the total volume column on your data sheet. Dump out the water. 2. Fill the cup with the 4mm beads up to the line you drew. 3. Using your graduated cylinder, slowly and carefully pour water into the cup until the water reaches the top of your sample. Write the volume of water remaining in the graduated cylinder on your date sheet. 4. Subtract the volume remaining from the total volume. This is the amount of water added to your sample. Write the volume of water added to the sample on your data sheet this is the pore space. 5. To determine the porosity of the sample, divide the pore spaces volume by the total volume and multiply the result by 100. Write the porosity on your data sheet. (Note: % pore space = pore space / total volume X 100)

2 Data Table: Sample Total Volume Volume Remaining in Cylinder 4 mm 100 ml 7 mm 100 ml 12 mm 100 ml Pore Space (Volume of Water poured in cups) (% pore space) Questions: 1. What is the relationship between particle size and porosity? 2. What is the relationship between particle shape and porosity? 3. Describe how mixing the of all the particles will affect the porosity of the sample as compared to particles A,B & C. Why? 4. Was your hypothesis correct? How did the data support it? 5. Complete the graphs below. Particle Size Particle Shape (increasing roundness) Particle Sorting (becoming more sorted)

3 PART 2: PERMEABILITY Purpose: To explain the relationship between particle size and permeablility. Background: When water falls from the sky and hits the ground it may do one of three things: evaporate immediately, run off to lakes or streams, or infiltrate. Permeability is the ability to let water pass through. In some places, rainwater will infiltrate (soak in) very quickly, while in others it will form puddles and sit on the surface for many days before finally soaking into the ground. In this investigation, you will explore the reasons why some soils allow water to soak in rapidly while others keep it on the surface. Hypothesis: Materials: For each group: * small funnel * beakers * cotton balls * stop watch * test tube rack * 100 ml graduated cylinder * gravel * sand * soil * clay Procedure: 1. Place a small, clean piece of cotton in the neck of a funnel. Fill the funnel above the cotton with gravel. Fill the funnel about two-thirds of the way. 2. Measure. Pour water into the graduated cylinder until it reaches the 50 ml mark. 3. With the bottom of the funnel over the beaker, pour the water from the graduated cylinder slowly into the sand in the funnel. 4. Measure. In the data table below, keep track of the time from the second you start to pour the water into the funnel. Measure the amount of time that it takes the water to drain through the funnel filled with coarse sand. 5. Record the time it takes for the water to drain through the sand in the data table. 6. Record the amount of water collected in the Beaker. 7. Empty and clean the measuring cylinder, funnel and beaker. 8. Repeat steps 1 through 7, first using sand, soil and then clay.

4 DATA TABLE Material Gravel Time Needed for Water to Drain Through the Funnel Water Collected in Beaker (ml) Water Retained (ml) Sand Soil Clay Analysis: Create a bar graph for the time needed for water to drain for the different materials below and a line graph for the water collected in the beaker and amount of water retained. Water Collected Water Retained Questions: 1. Which material is most permeable? 2. Which material is least permeable? 3. What is the relationship between particle size and permeability?

5 4. Was your hypothesis correct? How did the data support it? 5. Which particle would have the highest capillarity? 6. What is the relationship between particle size and capillarity? 7. Which would have a higher permeability, well sorted sediment or poorly sorted sediment? Explain. 8. Why do parking lots tend to have a lot of puddles and standing water? 9. The diagram below represents three identical beakers filled to the same level with spherical beads. If the packing of the beads within each beaker is the same, which graph best represents the porosity within each beaker?

6 Base your answers to questions 10 and 11 on the diagram below, which shows four tubes containing 500 milliliters of sediment labeled A, B, C and D. Each tube contains well-sorted, loosely packed particles of uniform shape and size and is open at the top. The classification of the sediment in each tube is labeled. 10. Each tube is filled with water to the top of the sediments and the tube is covered with a fine screen. The tubes are tipped upside down so the water can drain. In which tube would the sediment retain the most water? (1) A (3) C (2) B (4) D 11. Which tube will have the greatest capillarity? (1) A (3) C (2) B (4) D 12. Sediment samples A through D below have the same volume and packing, but contain different percentages of various particle sizes. Sample A: 75% clay and 25% silt Sample B: 25% clay and 75% sand Sample C: 50% pebbles and 50% sand Sample D: 50% pebbles and 50% cobbles Which sample most likely has the greatest permeability? (1) A (3) C (2) B (4) D 13. Which soil characteristic allows greater amounts of water retention? (1) large-size particles (3) high-density particles (2) small-size particles (4) low-density particles 14. A paved blacktop parking lot was built on what was once a soil-covered field. This area will now experience increased runoff when rain occurs because the paved parking lot has (1) less capillarity (3) greater infiltration (2) less permeability (4) greater porosity