Density

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Density
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Drill

• Which type of emergency drill would Ms. Massella
  announce over the PA system if we had an
  earthquake?
• Where is our secondary evacuation location if we
  have a serious fire, or emergency drill, in the
  building?

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Objectives

• iWBAT
• Show mastery of safety rules on a safety quiz.
• predict whether an object has a higher or lower
  density than water.
• solve density problems.
• Perform a density lab to determine the density of
  an object.

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Do you know the density of water?

• What is the density of pure water?
• The density of water is 1 g/ml

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Sink or Float

• Does a cork sink or float in water ?
• Is the density of a cork more or less than
• 1 g/ml ?

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Density Equation

• Do you remember what the Density equation is from
  the Accuracy/Precision lab?
• Density _mass____
• volume
• What are the units used for mass?
• What are the units used for volume?
• What would be the units for density?

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Lets try some problems.

• Set up the equation and solve for density.
• The mass of an object is 6.5g and the volume is
  4.8 ml, what is the density of the object?
• Ans 1.35 g/ml

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Lets try some problems.

• Solve for density.
• The mass of an object is 1.09 g and the volume is
  3.72 ml, what is the density of the object?
• Ans 0.29 g/ml

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Lets try some problems.

• Set up the equation and solve for mass.
• The density of an object is 5.12 g/ml and the
  volume is 7.07 ml, what is the mass of the
  object?
• Ans 36.2 g

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Lets try some problems.

• Solve for mass.
• The density of an object is 1.11 g/ml and the
  volume is 2.55 ml, what is the mass of the
  object?
• Ans 2.83 g

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Lets try some problems.

• Set up the equation and solve for volume.
• The density of an object is 10.2 g/ml and the
  mass is 4.99g, what is the volume of the object?
• Ans 0.49 ml

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What happens if the object is a cube or
rectangle?

• Instead of using ml that you read off of a
  graduated cylinder, you can find the volume of
  the object by measuring with a meter stick.
• Do you remember how to determine the volume of a
  cube?
• Length x width x height

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Cube volume units

• If you use length x width x height to determine
  the volume, what will the units be?
• The units will be cm3
• Note If you multiply the numbers, you also need
  to multiply the units.
• Ex 3 cm x 2 cm x 1 cm 6 cm3

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Practice Problem

• Set up the equation and solve for volume.
• The density of block of metal is 0.65 g/cm3 and
  the mass is 2.47g, what is the volume of the
  object?
• Ans 3.8 cm3

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Density Practice Problems

• Pick up a copy of the Density worksheet.
• Try working out the problems.
• Remember to show all of your work.

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Wrap Up

• I will switch to the Sink or Float ppt.