Measurements and Density

By the end of today’s lesson, be able to:
1.) Calculate mass, volume, and density
2.) Measure to one digit of uncertainty

A measurement of “compactness”: how close
the atoms are to one another
Mass
Volume
Density =
Mass
Volume


Mass = measurement of the amount of
matter (atoms and molecules)
Volume = the amount of space an object
occupies

Calculate the mass of a rectangular prism
WITHOUT putting it on the balance!
◦ HINT: Make some measurements and calculate the
volume.
Color of Block
Color of Tape
Density (g/cm3)
Paper-white
Green
0.541
Black
white
0.967
Cloudy-white
Orange
0.910
Clear
Red
1.17
Gray
Yellow
1.42
Number
15.2
Measurement
15.2 mL
Apple + Shadow Width = 14 cm
,
0cm
,
10cm
,
20cm
,
30cm
Apple + Shadow Width = 14.4 cm
,
0cm
,
10cm
,
20cm
,
30cm

Measure at the bottom of the meniscus

Calculate the mass of a rectangular prism
WITHOUT putting it on the balance!
◦ HINT: Make some measurements and calculate the
volume.
Color of Block
Color of Tape
Density (g/cm3)
Paper-white
Green
0.541
Black
white
0.967
Cloudy-white
Orange
0.910
Clear
Red
1.17
Gray
Yellow
1.42


Which mass was closer?
What is the percent error of your two
calculations? (0% error is perfect; there is NO error)


To determine the number of sig figs and use
them for rounding
To show set up for unit conversion (factorlabel method)
1)
2)
3)
All nonzero numbers are significant
“Placeholder” zeros are not significant.
Measured zeros are significant
(Atlantic/Pacific Rule)
In scientific notation, ALL numbers written
before the “x 10exp” are significant
1.230 x 104
90.210
0.0090210
90210.
90210
1)
2)
Multiplication/Division: Report the same
number of sig figs as the value with the least.
90210 x 90.210 = 8137844.1
Addition/Subtraction: Report the same
number of decimal places as the value with
the least.
90210 + 90.210 = 90300.21

A unit equation is a simple statement of two equivalent
quantities.
◦ 1 km = 1000 m
◦ 1 cm = 0.01 m
◦ 100 cm = 1m



100 cm = 1 m
“centi” (c)
1000 mm = 1m
“milli” (m)
1 km = 1000 m
“kilo” (k)
Prefixes can be
applied to ANY unit,
like grams or Liters

A unit conversion factor, or unit factor, is a ratio of two
equivalent options.

For the unit equation 60 minutes = 1 hour, we can write
two unit factors:
1 hour
60 minutes
or
60 minutes
1 hour
=1

Start with your given value in fraction form
“7.39 dollars”

7.39 dollars
____________
1
Treat units like variables so that they will
cancel.
7.39 dollars
1 quarter
____________ x _____________
1
0.25 dollars
7.39 dollars
dollars
____________ x _____________
1
quarter

If you have $7.39, how much is this amount
in quarters?

A candy bar is approximately 220 grams.
How many ounces is this?

If there are 24.6 blips to every zazzle and
there are 5.7 pinches to every blob and 3
blobs in a zazzle, how many blips are in 0.95
pinches?

Density of an object is 4.90 g/mL what is the
density of this object in pounds per Liter?

A cube is measured to have a volume of
13,506m3, what is this volume in km3 ?