6-8 > Physical Science
 Grade level: 6-8 Subject: Physical Science Duration: Two class periods
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Antarctica: Planet of Ice

Students will understand the following:
 1 Salinity (amount of salt) of water affects the buoyancy (floatability) of ice when the water is frozen. 2 The greater the salinity of an iceberg, the smaller the percentage of the iceberg that will remain beneath the surface of the water. 3 The size of an iceberg has no affect on the percentage of the iceberg remaining beneath the surface of the water.

You will need access to a freezer. The following materials will be required for each group of students:
 • Four paper cups (two large and two small) • Tap water • Salt • A measuring cup • A large clear plastic container • A ruler

1. Explain to the class that they are going to design and conduct an experiment to demonstrate the affect of salinity, or amount of salt, on floating icebergs. Their experiments will answer two questions: Does the presence of salt in an iceberg make the iceberg more or less buoyant (floatable)? and Does the size of an iceberg affect its buoyancy (floatability)?
2. Divide the class into groups of four. Instruct each group to form ahypothesisby guessing the answer to each question. Students should use any prior experience or knowledge of buoyancy and the properties of water to help them make informed guesses. Have each group write its hypothesis on a sheet of paper.
3. Next, have the groups hold brief discussions to come up with a plan for testing their hypotheses. (Students’ plans should include testing smaller and larger ice samples made from both fresh and salt water.)
4. Give each group the materials in the materials list. Instruct each group to create four model icebergs by freezing the contents of the four paper cups as follows: one small cup filled with plain tap water, one large cup filled with plain tap water, one small cup filled with salt water, one large cup filled with salt water. (Students can create salt water by dissolving 50 grams of salt in a half liter of tap water.)
5. Tell the class that when their icebergs are frozen, they will remove them from the cups and float them, one by one, in a clear plastic container filled with tap water. Ask students how they will accurately test their hypotheses. (Their answers should involve measuring the heights of the parts of the icebergs both above and below the surface of the water.)
6. Have students measure the height of each iceberg with a ruler; then have them separately measure the part of each that is above and below the surface of the water. Next have students calculate the percentage of each iceberg that is below the surface of the water. They should record their findings on a chart, such as this one:
 Fresh Salt Large % below surface % below surface Small % below surface % below surface
7. Have groups discuss their findings and determine whether the findings confirm their hypotheses. Students should conclude that because the percentages are the same for the large and small icebergs that are both fresh and the same for the large and small icebergs that are both salt, size has no affect on the buoyancy of an iceberg. Because the percentages for both the large and small saltwater icebergs are lower than those for the freshwater ones, students should conclude that the higher the salinity, the more buoyant an iceberg will be.

 Adaptations for Older Students:Older students could add to the experiment two more icebergs, one large and one small, that are made with salt water of lower salinity (25 grams of salt to a half liter of tap water).

 1 Many people think of Antarctica as being an area of ice and nothing else, but this is not the case. Describe the habitat of Antarctica. What details do you know about its flora, fauna, and environmental conditions? 2 When do the four seasons occur in Antarctica? What is the weather like in each season? Compare Antarctica’s seasons and weather to your hometown climate. 3 Describe the breeding cycle of emperor penguins. How does it compare to the breeding cycles of reptiles? 4 Compare explorations of Antarctica today with those of Robert Falcon Scott in 1908. What new equipment is available for Antarctic scientists? Create a list of equipment that scientists might need to deal with the harsh conditions. 5 Animals have both physical and behavioral adaptations that help them survive in their habitats over time. Compare the adaptations of a common wild animal in your local area with those of emperor penguins. Include in your comparison body structure, appearance, surviving extreme temperatures (hot or cold), internal chemistry, and group behavior. 6 Scientists consider Antarctica to be a “canary in the mineshaft” for the study of global climate—if anything bad is going to happen to the world’s climate, it should happen to Antarctica first. Discuss what scientists are learning from their studies of Antarctica. Are their findings positive or negative?

 You can evaluate your students on their experiments using this three-point rubric: Three points:experimental plan includes comparing buoyancy of saltwater and freshwater model icebergs, each of smaller and larger size; experiment carried out carefully; results recorded accurately; correct conclusion drawn  Two points:experimental plan includes comparing buoyancy of saltwater and freshwater model icebergs, each of smaller and larger size; experiment carried out adequately; results recorded with only partial accuracy; correct conclusion drawn  One point:experimental plan includes comparing buoyancy of saltwater and freshwater models or large and small models, but not both; experiment carried out adequately; results recorded with only partial accuracy; correct conclusion drawn with regard to property tested (salinity or size) You can ask your students to contribute to the assessment rubric by determining criteria for careful experimentation and accurate recording.

 Mapping Antarctica Give your students a blank outline map of Antarctica with a clear legend and ask them to use atlases and maps to find and label the following locations: the point of highest elevation, the point of lowest elevation, the South Pole, McMurdo Station, the Weddell Sea, Cape Crozier, the East Antarctic Ice Sheet, the Ross Ice Shelf, the Indian Ocean, the Pacific Ocean, the Atlantic Ocean, and the Transantarctic Mountains. The Antarctic Treaty What is the Antarctic Treaty? Divide your students into 15 pairs or small groups. Assign one group to research the origin of the treaty. (The complete text of the treaty is available online athttp://sedac.ciesin.org/pidb/texts/antarctic.treaty.protocol.1991.html.) When was it signed? What countries were responsible for its development? Why was it necessary? Assign each of the other groups one of the treaty’s 14 articles. What conditions does it refer to? Why was it necessary? What is its importance? Once the groups have completed their research, have them each give a brief presentation to the rest of the class. You can then lead a class discussion or debate about the treaty as a whole. Have its goals been achieved? Is it too restrictive? Is it restrictive enough? Are there other articles that students believe should have been included in the treaty? Antarctica

 Penguins: A Portrait of the Animal World Derek Hastings. Smithmark Publications, 1997.Color photos enhance the tale of the penguin, an amazing animal with remarkable adaptations for survival in the harshest of environments. issues related to genetic engineering. Antarctica: A Guide to the Wildlife Tony Soper. Globe Pequot Press, 1997.The storm-tossed Southern Ocean and the inhospitable landscape of Antarctica combine to form one of the last true wildernesses on Earth. Tony Soper’s lively book offers a deeper understanding of this unique continent.

 Blue Ice: Focus on Antarctica An exciting virtual field trip to Antarctica that takes place on the Internet as classrooms grades 4 - 8 work together to discover the continent. Penguins Features information about penguins’ special characteristics which allow them to survive in the severe climate of the Antarctic. Includes classroom activities. Web pages are part of the Gulf of Maine Aquarium web site. SeaWorld Animal Information Database Web site provides information about penguins and sea animals from a variety of biomes and educational resources. Sea World has a special penguin exhibit. Virtual Antarctica A gallery of images and information about habitat, animals, and birds of Antarctica. Records TerraQuest’s expedition to Antarctica. Antarctica Online An Australian Antarctica web site, featuring resources, a data center, atlas, environmental information, and live happenings. Click on “Resources” on the home page to access “Antarctica Classroom”. Gateway to Antarctica An extensive web site with scientific and educational information. Antarctica: The Longest Night Includes vocabulary, questions, activities, book titles, and web links. Part of Discovery Channel School’s lesson plans.

 Click on any of the vocabulary words below to hear them pronounced and used in a sentence. Definition:Adjustment to environmental conditions. Context:Penguins’ round bodies and small feet and flippers are all heat-saving adaptations that allow them to survive harsh Antarctic winters. Definition:A narrow opening resulting from a split or crack. Context:One of the great dangers to Antarctic explorers is falling into a crevice. Definition:To sit on eggs so as to hatch them by the warmth of the body. Context:Male emperor penguins incubate their eggs until they hatch by holding the eggs on their feet. Definition:A cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air. Context:Air-filled cavities called sinuses in the skulls of penguins are adapted to warm the air the penguins breath out, which in turn warms the air they breath in, enabling the penguins to recover 80 percent of their body heat. Definition:Happening, existing, or arising at precisely the same time. Context:During the courtship ritual, emperor penguins are able to make their body clocks synchronous with each other, which helps mating to occur successfully.

 This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.  Grade level:6-8 Subject area:science Standard: Knows about the diversity and unity that characterize life. Benchmarks: Knows evidence that supports the idea that there is unity among organisms despite the fact that some species look very different (e.g., similarity of internal structures in different organisms, similarity of chemical processes in different organisms, evidence of common ancestry). Grade level:6-8 Subject area:science Standard: Understands the genetic basis for the transfer of biological characteristics from one generation to the next. Benchmarks: Knows that reproduction is a characteristic of all living things and is essential to the continuation of a species. Grade level:6-8, 9-12 Subject area:science Standard: Understands how species depend on one another and on the environment for survival. Benchmarks: (6-8):Knows that organisms can react to internal and environmental stimuli through behavioral response (e.g., plants have tissues and organs that react to light, water, and other stimuli; animals have nervous systems that process and store information from the environment), which may be determined by heredity or from past experience. (6-8):Knows ways in which species interact and depend on one another in an ecosystem (e.g., producer/consumer, predator/prey, parasite/host, relationships that are mutually beneficial or competitive). (6-8):Knows that all individuals of a species that occur together at a given place and time make up a population and that all populations living together and the physical factors with which they interact compose an ecosystem. (6-8):Knows relationships that exist among organisms in food chains and food webs. (9-12):Knows how the interrelationships and interdependencies among organisms generate stable ecosystems that fluctuate around a state of rough equilibrium for hundreds or thousands of years (e.g., growth of a population is held in check by environmental factors such as depletion of food or nesting sites, increased loss due to larger numbers of predators or parasites). Grade level:6-8, 9-12 Subject area:science Standard: Understands the cycling of matter and flow of energy through the living environment. Benchmarks: (6-8):Knows how energy is transferred through food webs in an ecosystem (e.g., energy enters ecosystems as sunlight, and green plants transfer this energy into chemical energy through photosynthesis; this chemical energy is passed from organism to organism; animals get energy from oxidizing their food, releasing some of this energy as heat). (9-12):Knows that the complexity and organization of organisms accommodate the need for obtaining, transforming, transporting, releasing, and eliminating the matter and energy used to sustain the organism.

 Mary C. Cahill, middle school science coordinator, Potomac School, McLean, Virginia.