Topic Aim: Do Now:

Topic: Measurement
Aim: Describe density and how it is measured.
Do Now:
1. Identify the instrument and units used to
measure volume of a liquid? Of a regular solid?
2. Identify the instrument and units used to
measure mass.
3. Identify the instrument and units used to
measure mass.
HW: 1. Research and hypothesis due on
Wednesday 10/3.
2. Get Lab Safety Contract signed by
parent/guardian.
Density • Mass per unit volume
Which box has a greater density?
B
A
• Box A has a greater density
than Box B
• Why? Because it has a greater
mass (more matter/ molecules)
• Density of water = 1 g/mL
• Density = mass = m
volume v
Example #1: What
is the density of a
metal block that
has a mass of
525g and the
volume is 50cm3?
•D = m
v
•D = 525 g
3
50 cm
•D = 10.5 g
3
cm
Example #2: The
metal block was
split in half. The
mass of each half
is 262.5g and the
volume of each
half is 25cm3.
Calculate the
density.
•D = m
v
•D = 262.5 g
3
25 cm
•D = 10.5 g
3
cm
What is
the block
made of?
Silver =
10. 5
g/cm3
What happens
to the
density of a
block if you
cut it in
half?
• IT DOES NOT
CHANGE!!!
M = 20 gm
V = 10 mL
Density = 20/10 = 2 gm/mL
Cut the block in half
M = 10 gm
V = 5 mL
Density = 10/5 = 2gm/mL
It remains the
same !!!!
• Each pure substance has it’s own
density no matter what size it is.
•The density of water is
ALWAYS 1g/cm3!!!!
Example #3
• The mass of
a marble is
8.8 g. It
has a volume
of 2 mL.
What is the
density?
•D = m
v
• D = 8.8 g
2 mL
• D = 4.4 g
mL
Why will an • FLOATS when the
object float density of the
or sink?
object is LESS than
the density of the
liquid.
• SINKS when the density of the
object is GREATER than the
density of the liquid.
Less dense
than water
More
dense
than
water
Warm air rises bc it is less
dense than cold air which sinks.
Let’s summarize…
1. What is the equation for determining density?
2. What do you know about the density of
different substances?
3. Identify the density of water?
4. What would happen to the density of a
substance if it was cut into four pieces?
5. Why do substances float in water?
6. Why do substances sink in water?
Review:
1. The units of density could be
a. milliliters per gram
b. milliliters
c. gram
d. grams per milliliter
2. What is the density of a 40gram object with a volume of
20 milliliters?
a. 2 g
b. 2 ml/g
c. 2 g/ml
d. 2 ml/g
3. A cube is 1 cm on each side
and has a mass of 2 grams.
Will it float?
a. yes
b. no
c. The only way to tell is to put it in
water.
.
4. The density of water is
a. 1 mL/g.
b. 1 g/L.
c. 1 g/mL.
d. 1 kg/mL.
5. An object that floats in
water has a density of
a.less than 1 g/mL.
b.equal to 1 g/mL.
c.greater than 1 g/mL.
d.equal to 10 g/mL.
1. Will an object with a density of
3
3.4gm/cm sink or float in a
cup of water? Explain why.
2. Will an object with a density
of.086gm/cm3 sink or float in a
cup of water? Explain why.
• http://ippex.pppl.gov/interactive/matter/den
slab.html