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ENTROPY DEMOKATIE NOONAN Oakland High School 1023 MacArthur Blvd. Oakland, CA 94610 email: AEKNoonan@aol.com ********************************************************************************************* TYPE OF ACTIVITY: ADVANCE ORGANIZER, DEMONSTRATIONTARGET AUDIENCE: BIOLOGY, ADVANCED BIOLOGY, LIFE SCIENCEThis activity helps students understand the 2nd Law of Thermodynamics vis-a-vis living systems: (1) Entropy is constantly increasing on average (2) Living systems are highly ordered (3) It takes energy and work to maintain organization. Also (4) information is needed to maintain an ordered state. BACKGROUND:Define order, energy, work, information, entropy.Preparation time:5 minutes after materials are assembledClass time: 10-20 minutesMaterials needed:Plastic containers, cups, cardboard rolls (soft, lightweight materials for tower). This is a good time to take snapshots. I make a poster "Why do cells need energy?" using the pictures and student drawings.ACTIVITY:Have an elaborate tower built on the front table as the students walk in. Ask the students to make a detailed drawing of the tower and describe in it words. Solicit descriptors such as intricate, symmetrical (or asymmetrical), organized, etc. Say, "This tower will help us illustrate an important Law of the universe and how it affects cells. I need 2 volunteers to help with a demonstration. They will not be harmed, but they will have to be good sports." (Choose your volunteers wisely. Have them come up and stand on either side of the tower.) (... to class) I am going to ask each volunteer to do something with this tower, and then we are going to interview the person about his/her experience." To 1st volunteer: O.K., Susie, your job is to knock the tower down .... carefully so as not to hit classmates, but completely! (Caution: Make sure there is adequate space so that people in the front row will not be hit with flying objects).Oh-oh! you missed something -- I said completely!(in voice of T.V. announcer with paper-towel roll "microphone" for added drama) Now, Susie, tell us, was that difficult for you to do? Did it take a lot of energy? Was it kind of fun? Be honest! Thank you, Susie. You have earned your extra credit. Now (turning to John), your job is to put it back the way it was -- exactly! Come on! You said you'd be a good sport. You want that extra credit, don't you? Student usually grumbles and class laughs -- so s/he does have to be good-natured. Point out far-flung pieces. Make sure every piece is back on the table. To class: is this back the way it was? No? What do you need, John, to put it back? OH! You need information, a blueprint for building the tower. (Student may get his/her drawing and fumble around with rebuilding, but usually gives up.) (as announcer) Let me ask you, John, about your experience here today. Was it easy to do your part in this demo? (No.) Was it fun? (Heartfelt no!) Would you describe it as work?? (Yes!) Thank you for participating and being a good sport. To whole class: Now, in what ways are our cells are kind of like this tower? Are they organized? Do they have structure? (solicit knowledge of cell structure). Are there forces in the environment that act to destroy the cell's structure? Yes! from random motion of molecules, to physical forces and chemical attack, the environment is full of agents capable of destroying the cell's vital structure. The demo tells us that it is easy to break down organization. This is a Law of the universe -- the Second Law of Thermodynamics: disorder or entropy is constantly increasing on average in the universe. If this is true, how can cells maintain their highly ordered structure? Here's where the second part of the demo comes in. It takes energy, work, and information to maintain order. This tells us that cells need energy just to stay the way they are and not break down. (This is why we have to eat. This is why our bodies burn a significant amount of calories when we are not even exercising.) They also need to store information for rebuilding and reproducing. Summation:In this unit we will study the chemical processes that give cells the energy they need to fight entropy. Later, we will learn about the ways cells store information and use it to maintain their order and to reproduce.Get class to rebuild the tower for next period. Extension:I make a poster recapping the demonstration using photos of the students knocking down the tower, picking up pieces, and puzzling over how to rebuild it.WHY DO CELLS NEED ENERGY?I. Cells are highly organized like the tower we built.(Paste on photo of volunteers standing beside tower, and/or a student drawing of tower)II. According to the Second Law of Thermodynamics, disorder (entropy) is always on the increase.It is easy and fun to break down organization. (Paste action shot of student knocking down tower).III. It takes work and information to maintain order.(Paste picture of student picking up pieces and puzzling over how to put them back the way they were.)IV. Cells need energy: to maintain their orderto repair themselvesto growto reproduceStudents love to look at the pictures, and the lesson is reinforced as they view them.
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