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!
Slide 3
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!
Slide 4
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!!
Slide 5
Density Triangle
Slide 6
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)
Slide 7
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)
Slide 8
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
Slide 9
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!!
Slide 10
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!!!
Slide 11
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!
Slide 12
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
Slide 13
Temperature An increase in temperature causes a DECREASE in
density!! This is because volume increases when heat is
applied
Slide 14
Pressure An increase in pressure causes an INCREASE in
density!! This is because as pressure increases on something, its
volume decreases!
Slide 15
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)
Slide 16
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