Instructor’s Copy
Lab Worksheet – Don’t Be Dense
ALL DATA DEPENDS ON THE SUBSTANCES USED and should be tested before lab.
Table 1: Density of a gas
Initial mass of
Final mass of
Mass of gas given Volume of gas
Density of gas
substances (g)
substances (g)
off (g)
(mL)
(g/mL)
Table 2: Density Of A Regularly-Shaped Object
Mass of object Length of
Width of
Height of
Volume of
(g)
object (cm)
object (cm)
object (cm)
object (cm3)
Table 3: Density of An Irregularly-Shaped Object
Mass of object (g) Initial volume of
Final volume of
Volume of object
water (mL)
water and object
(mL)
(mL)
Mass of empty
beaker (g)
Table 4: Density of a Liquid
Final mass of
Mass of liquid (g) Volume of liquid
beaker and liquid
(mL)
(g)
50 mL water
Density of
object (g/cm3)
Density of object
(g/mL)
Density of liquid
(g/mL)
≈1
75 mL water
≈1
100 mL water
≈1
10 ml syrup
›1
Observation: Which floated, water or syrup? Water
QUESTIONS:
1. Could the water displacement method (density of an irregularly-shaped object) be used to
determine the volume of a rectangular solid as well as an irregular solid? Yes.
Explain. Doesn’t matter what shape it is as long as the object sinks.
2. If an object with a density of 5 g/cm3 is cut into two equal pieces, what is the density of each
piece? Density does not change with size since mass and volume both are halved.
3. The diagrams below represent three samples of the same substance, each having a different size
and shape. Arrange the letters of the sample to show the order by volume from largest to smallest.
C, A, B
What is the density of A? 3 g/cm3
B? 3 g/cm3
C? 3 g/cm3
4. Explain how the results of this laboratory investigation show that differences in size and shape do
not affect the density of a given substance.
Both the bar and the cube of iron, copper, or aluminum have the same density regardless of
shape. The five samples of clay have the same density regardless of size.
5. Why is density such an important physical property?
Every substance has a characteristic density, so density can be used to identify an unknown
substance. Also, because density is mass per unit volume, substances can be compared to
one another accurately.
6. Which would take up more space, 50 g of lead or 50 g of styrofoam? 50 g of Styrofoam.
Explain. It is less dense and more of it would be needed to get 50 g.
7. The density of water is 1 g/cm3. An object will float in water if its density is less than 1 g/cm3. If
its density is greater than 1 g/cm3, the object will sink. Given the following substances and their
densities, determine whether each substance will float or sink in water.
aluminum 2.7 g/cm3
arsenic 5.7 g/cm3
helium 0.18 g/cm3
S
S
F
gold 19.3 g/cm3
neon 0.89 g/cm3
lithium 0.53 g/cm3
S
F
F
chlorine 3.2 g/cm3
uranium 19.0 g/cm3
potassium 0.86 g/cm3
S
S
F
8. Substance X has a volume of 50 cm3 and a mass of 160 g. Will substance X float or sink?
160 g/50 cm3 = 3.2 g/cm3; sink
Substance Y has a volume of 140 cm3 and a mass of 112 g. Will substance Y float or sink?
112 g/140 cm3 = 0.8 g/cm3; float
9. Aluminum, gold and potassium are all put into the same container. They will form 3 different
layers based on their densities (shown in question 7). Show how they would be arranged.
potassium
aluminum
gold
10. You go to CiCi’s and the manager gives you a balloon. Why do helium-filled balloons float?
Helium is less dense than air so it floats.