Lab Addition to Ch. 2
- Density
Purpose:
To
compare the densities of aluminum, brass (an alloy or mixture of copper and
zinc) and acrylic.
Background:
Density
is a measure of the amount of mass per unit volume. A very dense substance has atoms and molecules
that are very tightly packed - in a less dense substance the atoms and
molecules are further apart.
density = mass/volume
Hypothesis: (you should examine the samples before making this
hypothesis)
____________
will have the highest density and _____________ will have the lowest density because
____________________________________________.
Materials:
electronic
balance ruler
or vernier caliper
cubes
of acrylic, aluminum and brass
Procedure:
1. Find the mass of each cube on the electronic
balance and record in the data table.
2. Find the length of one side of the cube (in
cm) using a metric ruler or vernier caliper and
record in the data table. Here is a link if you don’t know how to read a vernier caliper:
http://www.phy.ntnu.edu.tw/ntnujava/viewtopic.php?t=69
Data:
aluminum brass acrylic
Mass (g) ________ ________ ________
length of one side of a cube = _________ cm
Data Analysis:
calculate
the volume of the cube:
________
cm X
________ cm X ________ cm
= ________ cm3
calculate
the density of each cube:
aluminum ________
g /
________ cm3 = ________ g/cm3
acrylic ________
g /
________ cm3 = ________ g/cm3
brass ________
g /
________ cm3 = ________ g/cm3
Conclusion/Analysis:
1. List the metals from highest to lowest
density.
2. If you had a cube of styrofoam
the same size as the cube of iron, would its mass be more or less? Would its density be more or less? Why?
3. If you had a cube of styrofoam
the same mass as the cube of iron, would its size or volume be more or less?
Would its density be more or less? Why?
4. Is density a physical or chemical
property? Explain.
5. Describe a method for finding the density of
an iron cylinder.
Density and Floating
Purpose:
Why
does a cork float on water?
Background:
If
you made a little box one centimeter on each side and filled it with a liquid,
the box would hold one milliliter of liquid
(1 cm3 = 1 ml). Liters
and milliliters are units of volume, as are cubic centimeters and cubic meters.
Hypothesis:
If
you put a cork in water, it floats because ______________________________
________________________________________________________________.
Materials:
cork water
electronic
balance graduated cylinder
Procedure:
1. Find the mass of the empty graduated
cylinder. Record in data table.
2. Pour some water in the graduated
cylinder. Record the volume of water.
3. Find the mass of the water and graduated
cylinder.
4. Find the mass of the cork.
5. Since the cork is an odd shaped we are going
to find the volume in a different way than when we did the cubes. Fill the graduated cylinder halfway with
water and record the volume.
6. Put the cork in the water and push it under
the surface of the water with a toothpick.
Record the new volume of the water.
The volume of the cork is given by how much the volume of the water
rose.
Data & Calculations:
water:
mass of empty graduated cylinder: _______
g
mass of graduated cylinder & water: _______
g
mass of water (subtract the numbers
above): _______ g
volume of water: _______
ml
density of water = _______ g
/ _______ ml = _______ g/ml
cork:
mass of cork: _______
g
volume of water before cork: _______
ml
volume of water & cork: _______
ml
volume of cork (subtract the numbers
above): _______ ml
density of cork = _______ g
/ _______ ml = _______ g/ml
Conclusions and analysis:
1. How does the density of the cork compare to
that of water?
2. Based on your answer to #1, why does the cork
float on water?
3. Describe a method for finding the density of
an irregularly shaped object.
Density of a Liquid
http://www.edinformatics.com/math_science/dens_liquid.htm
Purpose: To identify an unknown liquid by its density.
What materials would you need if you were
going to find the density of a liquid?
Write a procedure for finding the density
of a liquid:
Now let's calculate the densities of the
two liquids using the following given data.
Liquid #1:
Given: Mass of empty graduated cylinder = 78 grams
Mass of graduated cylinder with unknown
liquid #1= 128 grams.
Find:
a) Mass of just the liquid = ____
b) Volume of liquid=_____
c) Density of liquid #1
=____
Liquid #2:
Given: Mass of empty graduated cylinder = 78 grams
Mass of graduated cylinder with unknown
liquid #2= 117.5 grams.
Find:
a) Mass of just the liquid = ____
b) Volume of liquid =_____
c) Density of liquid #2=____
Density of Liquid 1:
grams/cubic cm.
Density of Liquid 2:
grams/cubic cm.
What is each
liquid?
Using the table below it is now possible
for you to determine what each liquid is.
Densities for some common liquids are:
|
Substance |
Density (gm/cu.cm) |
|
Water |
1.00 |
|
Cooking oil |
0.92 |
|
Sea Water |
1.025 |
|
Carbon
tetrachloride |
1.58 |
|
Benzene |
0.87 |
|
Glycerin |
1.26 |
|
Methanol |
0.79 |
Unknown liquid #1 is:
Unknown
liquid #2 is: