Density!!!

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Density!!!
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What is Density?

• The density of a material is defined as its mass
  per unit volume.
• So what does that mean??
• How heavy something is in comparison to its size

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What are the Units?

• The proper SI unit is kg/m3
• We typically use g/mL or g/cm3
• Remember 1mL 1cm3
• How do we find mass?
• How do we find volume?

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How does Density affect us?

• In general, density can be changed by changing
  either the pressure or the temperature.
• Increasing the pressure will increase the density
  of a material.
• Increasing the temperature usually decreases the
  density

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So what does Density have to do with the Titanic?

• When it hit the iceberg, it ripped open and the
  bottom filled with water
• mass changed but not the volume

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Why else is Density important to us? It helps us
to float!!!This is called Buoyancy
Salt water is more dense so it makes it easier
for us to float
Density of water 1(100grams / 100ml of
water)Density gt 1 sinkDensity lt 1 float
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Practice with Density

• Density of water 1
• Buoyancy density less than or 1
• Rock has a mass of 10g and a volume of 5 mL
• Sinks
• Wood has a mass of 10 g and a volume of 20 cm3
• Floats
• To change Density, change the Volume!!!
• Air Craft carriers

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Demo 1 Pepsi Challenge

• PREDICT Which of the following drinks will float
  in the water? (in, not on top)
• Record your observations (you may make sketches)
  and provide an explanation for what took place in
  this demo. Be specific and include any change in
  the density (mass and volume) of the resulting
  mixture.

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Demo 2 WHAT IS 25 25?

• PREDICT When 25 mL of isopropyl alcohol and 25
  mL of water are combined, what will be the
  resulting volume?
• Record your observations (you may make sketches)
  and provide an explanation for what took place in
  this demo. Be specific and include any change in
  the density (mass and volume) of the resulting
  mixture.

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Demo 3 WHATEVER FLOATS YOUR BOAT

• PREDICT Will aluminum foil (D 2.7 g/cm3) sink
  or float when placed in water? Record your
  observations.
• PREDICT How can aluminum foil be altered to
  cause it to float? Record your observations.
• Record observations and explain what happens as
  more mass is added to the foil.