Transcript Activity 9 Title: Measuring Mass, Calculating Density Read pg. A-36 Problem: How can you use the mass and volume of an object to calculate its.

Activity 9
Title: Measuring Mass,
Calculating Density
Read pg. A-36
Problem: How can you use the
mass and volume of an object to
calculate its density?
Hypothesis/Initial Thoughts:
What is mass (in science!)?
•Mass is a measure of the number of
atoms in an object combined with the
density of those atoms. Usually people
measure mass in kilograms. You can
tell how much mass something has by
measuring how hard it is to get that
thing to change directions or slow
down.
What is the difference
between mass and weight?
• Mass is the amount of matter in an object.
• Weight is a measurement of a gravitational
force between two objects.
• People often get mass mixed up with
weight, because when you're on Earth, the
two are pretty much the same - things with
more mass also have more weight.
Mass vs. Weight
Mass vs. Weight
• On the Moon, an object weighs less
than it does on Earth because the Moon
is smaller and has less gravitational pull
on the object.
• An object will have the same mass on
both the Moon and on Earth because it
is taking up the same amount of space.
• Mass is not the same
as size - some big
things, like balloons,
are very light, while
some small things, like
a lead fishing weight,
are very heavy. A truck
would be the same size
whether it was empty
or full, but it would have
a lot more mass if it
was full - and it would
be even harder to stop.
Density
• In Activity 7, you looked at relative
density. What does that mean?
• These observations of density are
qualitative; they do not include
measurements, but only provide
comparisons with water or ethanol.
Density
• What is Density?
– Density is the mass per volume.
– Finding density through measurement is
quantitative
• Your job is to measure the density of
each object and see how the objects
compare to each other.
How do the densities of the light
gray and dark gray materials
compare with each other?
• Density = mass/volume
• Measure the mass and divide it by the
volume you calculated in Activity 8.
• UNITS!!!!
• Look at Table 3 on A-40
• Make sure to rotate who is taking the mass.
Balances
•
•
•
•
Handle carefully
Calibrate to Zero
Be ACCURATE!!!
Units?
–Grams
Data/Observations:
From Activity 8
Table 1: Mass, Volume, and Density of Six Objects
Object
Mass (g)
Volume (cm3
or mL)
Density calc.
Density
(g/cm3 or
g/mL)
Lt. gray bar
Drk. gray bar
Lt. gray cube
Drk. Gray
cube
Lt. gray
cylinder
Drk. gray
cylinder
44.105 g
15.6
cm3
15.6 cm3
d=
44.105 g
15.6 cm3
2.8 g/cm3
Discussion
• Compare your densities to
those of other groups.
• Why may they be different?
Does the density of a material
change if its size changes?
What do you think will happen
to the density of this clay if I
cut it in half?
• If a piece of clay that is 10 g in mass
and has a volume of 5 cm3 (density 2
g/cm3) is cut in half, what will be the
density of the two new pieces of clay?
Conclusion
• Mass and volume depend on the object.
• Density depends on the material the
object is made of.
• Density is independent of the amount of
the material
Unit A Major Concept
• Physical Properties can be measured
or observed using one or more of your 5
senses.
• Chemical properties of matter
describes its "potential" to undergo
some chemical change or reaction.
Unit A Major Concept
• Substances have characteristic
properties, such as density, that are
independent of the amount of the
sample.
• Density = Mass/Volume
in g/cm3 or g/mL
• 1 mL = 1 cm3
Unit A Major Concept
• To find the density of a regular object,
calculate the volume (length x width x
height) and then divide mass (g) by
volume (cm3).
• To find the density of an irregular object,
find the volume using water
displacement and then divide divide
mass (g) by volume (mL).
Unit A Major Concept
• If an object is more dense than a liquid,
it will sink.
• If an object is less dense than a liquid, it
will float.
• This is called relative density
Quiz Next Week!
• The quiz will be on the Unit A Major
Concepts (Mastery Quiz) and the Unit A
Vocabulary.