Density+PBL

Which weighs more a pound of feathers or a pound of lead?

__Identifying Fakes__
Is identifying fakes a useful skill? Can you determine how much gold is in a ring? Inferior or dangerous raw materials and products are being supplied to many US companies from foreign sources. This results in the buying of inferior or dangerous products by US consumers. Has anyone heard about this happening?

Density is a physical property that can be used to identify substances and determine if something will float. The worth of gold in jewelry can be determined by calculating its density. The quality of some raw materials for producing goods can be determined by calculating its density. Density can also be used to determine how much cargo of a certain type a ship can transport/float.

Each group will complete the following four tasks and record details about their investigations.

Task A: Let us suppose that these blocks were rings given to you and you wanted to determine what they were made of. Design a procedure for determining the density of the blocks. Explain the steps you would follow, including the equipment that you would use, and how you would use this equipment to determine the density of these blocks. Measure the density of 4 blocks and organize your measurements and data in a table. Use a density chart to conclude what the blocks are made of.

Task B: Let us suppose your team is applying to be a subcontractor that tests the quality of raw materials by testing their density. Your team is given four tubes to sort by density. Explain the steps you would follow, including the equipment that you would use, and how you would use this equipment to determine the density of these tubes. Measure the density of these tubes and organize your measurements and data in a table. Analyze your data using a graph to determine which tubes have the same density. Report your findings in a conclusion.

Task C: Let us suppose that your team was subcontracted to construct a boat to move a certain cargo. To show you could handle the task, calculate the buoyant forces on a floating tube when it contains two different sized pieces of iron. Explain the steps you would follow, including the equipment you would use, and how you would use this equipment to determine the buoyant force on the floating tube. Use Archimedes’ principle and show your calculations.

Record the following about your investigations: Address each of the following items starting with a topic sentence. 1. Tell what you are investigating and why. (Define your investigation.) 2. Tell what results your procedure will produce, how it will produce these results, and list the procedure’s steps. 3. Explain what equipment, measurements, and calculations will be used to obtain the data including units. 4. Make accurate measurements, observations, and/or calculations. 5. Organize the measurements and calculated data in some type of table. 6. Analyze the data and if it would be useful use a graph. 7. Explain the significance of the data and calculations. 8. Make a conclusion citing your data and/or calculations. 9. Attempt to write and spell well.

Use the following to guide the presentation of your findings. (Three levels of performance: A, C, or F) 1. Defined the task/task mostly defined/ description is off 2. Clear steps or procedure/mostly clear procedure/unclear procedure 3. Equipment use explained/mostly explained/kind of explained 4. Mass, volume, and density determined/Mostly/halfway 5. Complete data table / mostly complete / incomplete 6. Data analyzed/ mostly analyzed / incorrectly analyzed 7. Calculations correct/mostly correct/ half correct 8. Clear conclusion / cloudy conclusion / muddy conclusion 9. Presented well/ Decent presentation attempted/Sloppy 10. Presented well/ Decent presentation attempted/Sloppy 11. Presented well/ Decent presentation attempted/Sloppy 12. Presented well/ Decent presentation attempted/Sloppy

One characteristic that can be used to identify pure metals is density. If you determine the density of a pure metal, you can determine what the metal is, as shown in the table below.  (Brass is 2/3rds Copper and 1/3rd Zinc-estimate its density.)   Suppose that you have been given a ring and want to determine if it is made of pure gold. Design a procedure for determining the density of the ring. Explain the steps you would follow, including the equipment that you would use, and how you would use this equipment to determine the ring's density.    or to determine whether or not an object might float when put into water. Estimate, measure and calculate the density of objects and materials. http://www-personal.umich.edu/~lpt/archimedes.htm http://blog.abud.me/2011/08/density-dunk-using-inquiry-problem.html https://www.youtube.com/watch?v=P5SmW6IxfwI

Pipe & Iron Rod Lengths 1: 7/8 2: 1-3/4 3: 2-5/8 4: 3-1/2

1: 5/8 2: 1-1/4 3: 1-7/8 4: 2-1/2

Make an egg float in water by adding salt.

..

College Lab http://www.physics.arizona.edu/physics/gdresources/documents/13_Archimedes.pdf