DENSITY!!!

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This is NOT DESTINY….
DENSITY!!!
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!
Density Formula
 Density = Mass (grams) / Volume (cubic cm or





mL)
D = m/v
Remember…NO 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!
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=vxd
Write these down in your notes!!
Density Triangle
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)
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)
Volume of rectangular/square
objects
L=?, W=?, H=?
 V= L x W x H
 V = ? cc
 What if this block’s
mass is 320 g? What’s
its density?
 D = m/v
 d = 320g / ? cc
 D = ? g/cc
Volume of Irregular Objects
 Volumes of irregular objects must be
determined by water displacement
 We use a graduated cylinder for this! Let’s see
how to do this!!
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!!!
Volume of a liquid??
 This is MAD easy, yo!
 Just pour the liquid into
t graduated cylinder
and READ!
 So, what’s the volume
of the water in the
graduated cylinder on
the left?
 That’s right : 20mL!
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
V=20cc
D = m/v
D = 40g / 20cc
D = 2.0 g/cc
Temperature
 An increase in temperature causes a
DECREASE in density!!
 This is because volume increases when heat is
applied
Pressure
 An increase in pressure causes an INCREASE
in density!!
 This is because as pressure increases on
something, its volume decreases!
Earth
 In Earth, more dense materials tend to sink
toward the core
 Less dense materials tend to rise to the
surface
 Earth’s inner core is MOST dense
 The Outer Atmosphere is LEAST dense (due
to VERY light gases there)
Some other interesting tidbits…
 EVERYTHING on this planet is most dense in





its SOLID phase…well, 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
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