DENSITY!!!

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DENSITY!!!

• This is NOT DESTINY.

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What the heck is Density anyway?

• Density is the amount of matter (mass) contained
  within a given amount of space (volume)
• There is a formula for this, on the front page of
  the ESRT! What is this formula? Look at your
  ESRT!!
• Hurry up!

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Density Formula

• Density Mass (grams) / Volume (cubic cm or mL)
• D m/v
• RememberNO NAKED NUMBERS!
• ALWAYS include units and remember to round to the
  nearest 10ths
• 4 is not an answer for density
• 4.0 g/cc is an answer!

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Formula Manipulations

• You WILL NEED to manipulate this formula in order
  to solve for Volume and Mass
• If you manipulate this equation, you will get the
  following (USE THE DENSITY TRIANGLE!!)
• V m/d
• M v x d
• Write these down in your notes!!

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Density Triangle
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Determining the Mass

• Mass is the amount of matter contained within a
  given object
• It can be measured using an electronic balance or
  scale
• The proper units to measure MASS in is grams (g)

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Determining Volume

• Volume is the amount of space an object occupies
• It can be measured by either by using a ruler to
  obtain the LENGTH, WIDTH, AND HEIGHT of a
  rectangular/square object or by using water
  displacement
• The proper units for volume is cubic centimeters
  (cc) or milliliters (mL)

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Volume of rectangular/square objects

• L?, W?, H?

• V L x W x H
• V ? cc
• What if this blocks mass is 320 g? Whats its
  density?
• D m/v
• d 320g / ? cc
• D ? g/cc

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Volume of Irregular Objects

• Volumes of irregular objects must be determined
  by water displacement
• We use a graduated cylinder for this! Lets see
  how to do this!!

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Water Displacement in 3 steps

• 1) Place a certain amount of water into the
  graduated cylinder (20mL in this example)
• 2) Place the object into the water CAREFULLY, and
  record the new water level (it changed to 23mL in
  this example)
• 3) Now, subtract your old volume from the new
  volume 23mL 20mL 3mL
•  
• So the volume of this object is 3mL!!!

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Volume of a liquid??

• This is MAD easy, yo!
• Just pour the liquid into t graduated cylinder
  and READ!
• So, whats the volume of the water in the
  graduated cylinder on the left?
• Thats right 20mL!

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Size and Shape

• Size and shape of an object have NO EFFECT on
  density
• But size and shape DO have an effect on mass and
  volume!
• Check out this example

• Sample 1 m 20g and V 10cc
• D m/v
• D 20g / 10cc
• D 2.0 g/cc
• Sample 2 m 40g and V20cc
• D m/v
• D 40g / 20cc
• D 2.0 g/cc

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Temperature

• An increase in temperature causes a DECREASE in
  density!!
• This is because volume increases when heat is
  applied

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Pressure

• An increase in pressure causes an INCREASE in
  density!!
• This is because as pressure increases on
  something, its volume decreases!

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Earth

• In Earth, more dense materials tend to sink
  toward the core
• Less dense materials tend to rise to the surface
• Earths inner core is MOST dense
• The Outer Atmosphere is LEAST dense (due to VERY
  light gases there)

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Some other interesting tidbits

• EVERYTHING on this planet is most dense in its
  SOLID phasewell, almost everything
• WATER is the only exception
• Water is most dense in its LIQUID phase
• Water is most dense at 4 degrees C
• Pure water has a density of 1.0 g/cc
• When putting objects in water, less dense objects
  will float, more dense will sink, and equal
  density objects will float right in the middle