Name _______________________________Date _________________________Hour_______ What Determines whether an object floats or sinks? Pat and Sam are discussing why some objects float while others sink. Pat thinks that heavy objects sink and light objects float. Sam believes the size of the object is what matters, meaning if you have two spherical objects, the bigger one will sink and the smaller one will float. Your task is to determine which, if either, student is correct. Part 1: Test Pat’s Hypothesis 1. Go to http://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=362 At this site you are able to measure mass, volume (using water displacement), and use a tank filled with liquid to test whether each item floats sinks. When you mouse over the objects, a number will appear. We will use these numbers to identify each object. Be sure the density of the beaker of liquid is set to 1g/ml. 2. Left Column - Discuss your initial thoughts. Here are some topics to consider: What do you think about Pat’s hypothesis? What do you think about Sam’s hypothesis? What do you think determines whether an object will float? Look at the objects on the shelves in the simulation. Which of the objects on the shelf do you think will float? Which do you think will sink? Explain your reasoning. 3. Create a data table in the right column of your notebook. Your table will need three columns; Object #, Mass (g), and Float or Sink? Measure the mass of objects #1- #12, then rank them from lowest to highest mass in the data table. Sample Table Object # Mass (g) Float or Sink? 4. Do your results indicate a clear relationship between mass alone and whether an object floats or sinks? Explain your reasoning. (Left Column) Part 2: Test Sam’s Hypothesis. 5. Create a data table as shown below. Measure the volume of objects #1-#12, then rank them from smallest volume to largest. Sample Table Object # Volume (ml) Float or Sink? 6. Do your results indicate a clear relationship between size (volume) and whether an object floats or sinks? Explain your reasoning. (Left Column) Part 3: Another option – Density 7. Create a data table as shown below. Calculate the density for each object, then rank them from smallest density to largest. Sample Table Object # Density (g/ml) Float or Sink? 8. Do you see a relationship between density and whether an object floats or sinks? Explain your reasoning. (Left Column) 9. Left Column - Summarize your learning to this point: Here is a topic to consider: Which student, if either, Sam or Pat was correct? Explain your reasoning. Part 4: Can you make a sinking object float without changing the object? 10. Place one of the objects that sank back in the beaker. Slowly change the density of the liquid until the object floats. Once you get the object to float, what happens if you decrease the density? Try to make objects that were floating, sink, and objects that sank, float. Be sure to create a data table to record your results. Sample Table Object # Object Density Liquid Density at which Liquid density at which (g/ms) object changes from object changes from floating to sinking sinking to floating (g/ml) (g0/ml) 11. Summarize your learning for today’s activity. Here are some topics to consider: What did you do? What did you expect? What did you learn? Considering your data from Part 4, how many pieces of information do you need in order to determine whether an object will float or sink? Explain your reasoning. Assessment: Imagine the Rocky Mountains of Colorado. What do you see? Among the many sub-ranges that make up the Colorado Rockies, there are fifty-four summits that reach above 14,000 feet in elevation. No where else in the Rocky Mountain chain, which stretches from Texas to Canada, do the summits reach these heights. It is interesting that Colorado contains so many peaks over 14,000 feet in elevation yet not a single peak higher than 14,500 feet. Use the link below to help you explain why the peaks do not rise above 14,500 feet. http://www.globalchange.umich.edu/globalchange1/current/lectures/topography/topography.html Preview of Assessment Questions: 1. How is the Earth like the density column shown in class? 2. Why do the peaks of the Colorado Rockies never reach above 14,500 feet? 3. Discuss a change that would have to occur for the mountains to rise above 14,500 feet. There is more than one right answer to this question. 1. Get acquainted with the site. Scrolling down this web page, you will find the diagram below: The is the symbol representing density. Therefore, according to the diagram, saltwater has a density of 1.03. Located directly above the diagram is a simulation called “Isostasy”. Manipulate the data in this simulation to help you determine the answers to the assessment questions.
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