The students will be able to: define porosity and relate it to the capacity of a common object's TEKS ADDRESSED:

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1 AUTHORS NAMES: TITLE OF THE LESSON: Porosity and Permeability TECHNOLOGY LESSON : No DATE OF LESSON: TIME LESSON: 2 (60 min class) NAME OF COURSE Biology SOURCE OF THE LESSON: Lynn Kirby TEKS ADDRESSED: Biology 12E Investigate and explain the interactions in an ecosystem including food chains, food webs, and food pyramids 12D Identify and illustrate that long term survival of a species is dependent on a resource base that is limited Chemistry 4A Plan and implement investigative procedures including asking questions, formulating testable hypotheses and selecting equipment and technology Additional TEKS ( ) Environmental Systems c5b Aquatic Science c7c + 12 a,b Earth and Space Science a6c CONCEPT STATEMENT: A layer of sediment or rock that yields sufficient water for human use is called and aquifer. Good producing aquifers have two distinct qualities: they are both porous and permeable. The purpose of this lesson is to show what sediments have a higher porosity and permeablitility. PERFORMANCE OBJECTIVES: The students will be able to: define porosity and relate it to the capacity of a common object's 1

2 ability to hold a fluid define permeability and relate it to the capacity of a common object to transmit fluids describe the function of sediment in an aquifer and identify the best sediment to use in one. RESOURCES: 4 500ml graduated cylinders Sand, rounded gravel, angular gravel, gravel sand mixture 2 L Bottles (20) Ring stands Pitcher of water for each table Bucket to dispose of used water Stop watches to time the water SAFETY CONSIDERATIONS: None for this lab SUPLEMENTARY MATERIALS, HANDOUTS: Pre and post assessment. Lab handout Charts for determining porosity and permeability Engagement Ask the students how a sponge works. To demonstrate porosity: Show the students a sponge and a glass vase. Stick the sponge inside the glass vase to show the large volume of water that is absorbed by the What volume of water do you expect it to absorb without out water dripping away? If I pour this water on top of the sponge will it go through it and into the bottom of the 2 It absorbs water! not too much absorption. Yes. No. It will be blocked

3 Engagement sponge. glass? because you stuffed it in there. This is an example of an event that will surprise the students. To demonstrate permeability: Show what happens when a paper towel with marker on it absorbs water, and then the water transmits the ink upward. The water does not go through the sponge. Can any one tell me why this is occurring? But if the sponge has holes in it, why did the water not go through? It is in the glass to tight. The sponge takes up all the room. The holes are not connected. [adhesion and cohesion forces are stronger than gravitational forces] Exploration Assign groups by counting off students in numbers. Hand out a copy of the lab to each student. Show them the types of sediment being used. And then explain the lab for the porosity section. What sediment do you predict the water will travel faster through? What will retain more water? Would you want something with high porosity or They will be very distracted, hungry, and difficult (like last time). We will have to be a little more commanding and try to keep their attention right from the start. They will most likely predict the jaged rocks since they will have more spaces in them. 3

4 Exploration Quiz them on the lab procedure by calling on random students. Assist the students while they are performing porosity measurements. permeability in an aquifer? What would filter bacteria and other bad things from the water better? The soil sand mixture will hold more water. Both. After they have finished with porosity, explain the permeability section of the experiment, being sure to quiz the kids again about the procedure. Explanation Each of the groups will explain their results to the class. What was the rate of water flow through each of the sediments. Each group will have a different answer for their sediment. What does it mean to have a high porosity? Varying answers, hopefully the correct ones. 4

5 Explanation What does it mean to be higher permeable? Elaboration Take the results of a group that did well and explain how pockets of empty space led to a higher porosity (the measure of empty space of a substance) which leads to more water retained in the substance. Demonstrate how water likes sticking to itself and to the sides of things (perhaps by showing how water creeps through a paper towel with ink [since the water will transport the ink as a tracer] on the overhead), and explain how this type of behavior is exactly what happens with permeable substances. Once the students have finished the original lab have the students design a model that would best represent an ideal aquifer. This will be to What would be the best combination of material for an aquifer? 5

6 Elaboration extend on the information learned in the lab. Evaluation The post assessment will be handed out. They will not be happy to be taking another test. They will whine and complain but most should know the answers. Teacher Notes The sand and gravel can be purchased at a garden store. Regular art clay can be used for the clay sample. The pantyhose tend to break easily so have extra on hand and replace as needed. All of the empty bottles need to be the same size, but either 1 liter or 0.5 liter bottles will work, depending on the size of the rings you have for your ring stands. After getting 7 same sized bottles the teacher should cut the bottom of the bottles off so they are open and easy to fill. The cap end of the bottom stays untouched so that the lid can be taken off and put back on during the lab. Use a permanent marker to draw a line around each bottle 10 centimeters from the cap end. The teacher needs to measure and draw a black line to the same level on each of the bottles so that each bottle will contain the exact same amount of material to be tested. For a 0.5 liter bottle measure from the bottom of the neck 6

7 Possible answers to the conclusion questions and Sample Data Answers will vary widely with the provided materials. A range of answers is given below. Sample Porosity (ml) Flow time (min) Recovered water (ml) Permeability (ml/min) Gravel Coarse Sand Fine Sand Clay Which sample held the most water? Which held the least? The gravel held the most water, clay held very little or no water. 2. Describe the amount of available pore space in the material that held more water? The material that held the most water has the most porosity, or rather has the most space between particles to hold water. 3. Which sample was the most permeable? Which was the least permeable? Gravel was the most permeable. Clay was the least permeable. 7

8 4. Why would gravel be a poor filter for water? Which material might make a good filter? Gravel allowed the water to pass through too quickly to filter the water. Sand would be a much better filter. 5. Why would clay act as a confining layer (aquitard) for an aquifer? Clay does not allow water to pass through and therefore is an excellent confining layer. 6. Aquifers must be permeable. List the samples which would be good aquifers. Gravel and both types of sand would be good aquifers because they are both porous and permeable. 7. Discuss the truth of statement What goes in, must come out. How does your data support or refute this statement. The volume of water that was recovered was less than the volume of water that was added. Some of the water remained in the material clinging to the particles. Therefore, only some of what goes in comes out! 8

9 Experiment 14 Investigating Porosity and Permeability Aquifer Study Porosity and permeability are related terms used to describe any rock or loose sediment. Both of these properties are essential to the formation of an aquifer. Specifically, porosity of a rock is a measure of its ability to hold a fluid. Permeability is a measure of the amount of fluid able to flow through a rock. An aquifer is a geologic formation that will yield water to a well in sufficient quantities to make the production of water from this formation feasible for beneficial use. It contains permeable layers of underground rock or sand that hold or transmit groundwater below the water table. Artesian aquifers are confined on the top and bottom by non-permeable rock layers, sometimes called aquitards, which put the aquifer under pressure and allow springs and wells to flow without being pumped. Purpose Students will be able to describe porosity and permeability in sand, gravel, and clay. Materials fine sand clay gravel course sand rubber bands ring stand stop watch 1 or.5 liter carbonated beverage bottle with cap 100 ml graduated cylinder pantyhose 9

10 Procedure 1. In the space marked HYPOTHESIS on your student answer sheet, write a hypothesis addressing which of the four materials (fine sand, course sand, gravel, and clay) will be the most porous and which will be the most permeable. 2. Cut a 20 cm square of pantyhose and fold it in half. Remove the cap from the bottle, place the pantyhose over the opening of the bottle, and secure with a rubber band. 3. Replace the cap and firmly attach it so that water will not leak out of the bottle. See the picture. Pre-test your bottle with some water to ensure that it does not leak. 4. Empty the water from the bottle, and proceed to the next step. 5. Fill the bottle to the black line with the sample material that will be tested. 6. To measure the porosity we will determine the volume of water it takes to just saturate the test material. Fill the graduated cylinder to 100 ml. Slowly add water to the sample material until water begins to pool at the surface of the sample. If you have added too much water, carefully pour off the excess back into the graduated cylinder. 7. Record the volume of water in ml that was added to the sample in the data table in the Porosity column on your student answer page. Then, record this value for your class data as your teacher instructs. 8. To measure the permeability we will determine the amount of time in takes for 200 ml of water to flow through the sample material. Add the remaining water in your graduated cylinder to the sample container. Add any additional water to the sample so that the TOTAL VOLUME of the water added is 200 milliliters. For example, if you added 60 milliliters to the sample in the porosity test, you will have to add 140 milliliters more to the container. 9. Position a 250 ml beaker under the neck of the bottle to catch the run-off water. Simultaneously, start the stopwatch and remove the cap from the bottle. Stop the timer when the dripping water from the bottle has a frequency of one drop every 10 seconds. 10. Record the time in the data table on your student answer page in the Flow time column. Then, record this value for your class data as your teacher instructs. 10

11 11. Using the run-off water in your beaker, measure the amount of water that passed through your sample with a graduated cylinder. Record this value in the data table on your student answer page in the Recovered water column. Then record this value for your class data as your teacher instructs. 12. Using the volume of recovered water and the elapsed time, calculate the porosity in ml/min for each sample. Record these values in your data table in the Permeability column and with the class data as your teacher instructs. 11

12 Investigating Porosity and Permeability Aquifer Study HYPOTHESIS DATA AND OBSERVATIONS Sample Porosity (ml) Flow time (min) Gravel Coarse Sand Fine Sand Clay Recovered water (ml) Permeability (ml/min) ANALYSIS Make one graph that shows both porosity and permeability using the two y-axes to show the data. CONCLUSION QUESTIONS 1. Which sample held the most water? Which held the least? 2. What can you assume about the material that held more water? 12

13 3. Which sample was the most permeable? Which was the least/not permeable? 4. Why would gravel be a poor filter for water? Which material might make a good filter? 5. Why would clay act as a confining layer for an aquifer? 6. Aquifers must be permeable. List the samples which would be good aquifers. 13

14 7. Discuss the truth of statement What goes in, must come out. How does your data support or refute this statement. 14