Activity 3A: The Thickness of a Thin Aluminum Sheet
Prelab Questions
Express numerical answers to the correct number of significant figures.
1. What is the volume of a block that has the dimensions:
L = 8.20 cm, W = 2.25 cm, H = 1.00 cm?
V=LXWXH
V = 18.5 cm3
2. If the density of a substance is 0.525 g/cm3 and the volume of a sample
of this substance is 18.25 cm3, what is the mass of this sample?
M=DXV
M = 0.525 g X 18.25 cm3 = 9.58 g
cm3
3. A piece of paper is known to have an area of 30.2 cm2 and has a volume of
5.2 X 10-3 cm3. What is the thickness of this paper?
Thickness: Volume
Area
T= 5.2 X 10-3 cm3= 1.7 X 10-4 cm
30.2 cm2
Data
Be careful, your measurements should have the correct number of significant figures!!
Sheet No.
Type
1
Regular
2
Regular
3
Heavy
4
Heavy
Calculated Results
Length (cm)
9.85
9.85
17.71
15.20
Mass (g)
0.57
0.57
2.00
1.00
Volume (cm3) Thickness
(cm)
1
Regular
‘147’.75
0.’21’111
1.4 X 10-3
2
Regular
‘147’.75
0.’21’111
1.4 X 10-3
3
Heavy
“317.0”09
0.”740”74
2.34 X 10-3
4
Thin??
“228.7”6
0.”370”37
1.62 X 10-3
1. a) Compare your results with at least two other teams. How do your answers compare
with them?
Team members:
Regular(Ultra Thin) 1.1 to1.5 X 10-3 cm 0.0011 to 0.0015cm
Regular(Thin)
1.6 to 2.0 X 10-3 cm 0.0016 to 0.0020cm
Heavy(Thick)
2.1 to 3.5 X 10-3 cm 0.0021 to 0.0035cm
We may have 3 types of foil (cheap one-Zeller’s, regular, heavy duty)
b) Can you determine how accurate your measurements are? (Why and
Sheet No.
=
Type
Area (cm2)
Width (cm)
15.00
15.00
17.90
15.05
explain)
Yes, if we use a micrometer as it is more precise than a ruler
Measurement with a micrometer:
Heavy aluminum: 0.035 mm or 0.0035 cm
Regular thin aluminum: 0.020 mm or 0.0020 cm
Ultra thin aluminum: 0.0011 mm
2. How precise are your answers? Recall the definition of precision.
Precision deals with number of sig fig.
Our measurements are precise since they have as many sig figs as the micrometer.
3. If you had used a very crude balance that allowed only one significant figure, how would
this have affected your results for:
(provide a new number of sig fig)
Area? No effect, ruler measures with 2 decimal places
Volume?
Yes, since the mass is less precise, the volume would be less precise, 1 sf .
Thickness?
Yes, since the volume would be 1 sf, the thickness would also be 1 sf.
Synthesis
1. Could we used this method of measurement to determine the thickness of
an oil spill? What additional information would be needed?
Yes, if we know the oil density, area (size of spill), and
volume (haul size), of oil spill
2. A very thin layer of gold plating was placed on a metal tray that measured
25.22 cm by 13.22 cm. The gold plating increased the mass of the plate by 0.0512 g.
Calculate the thickness of the plating. The density of gold is
19.32 g/cm3. Show all your work and use the correct number of significant figures.
Road Map:
Thickness: Volume
Area
Area: length X width = 25.22 cm X 13.22 cm = 333.4 cm2
4 sf
4 sf
= “3.334”084 X 102 cm2
Volume: mass = 0.0512g X cm 3
density
1
19.32 g
Thickness: “2.65”0104 X 10-3 cm3 = 3sf
=
= 2.65 X 10-3 cm3
= 0.00”265”0104 cm3
=7.95 X 10-6 cm
“3.334”084 X 102cm2
4sf
= 0.000 007 95 cm
3. By mistake, a quart of oil (1.06 quarts = 1 liter =1000 cm3) was dumped
into a swimming pool that measures 25.0 m by 30.0 m. The density of
the oil was 0.750 g/cm3. How thick was the resulting oil slick?
Be careful with significant figures and scientific notation. (Show your work.)
Thickness: Volume
Area
Area: length X width
Volume: quart  cm3
Length: 30.0 m = ‘3 00’0cm = 3.00 X 103 cm
Width: 25.0 m = ‘2 5’00 cm = 2.50 X 103 cm
Area= (2.50 X 103 cm) X (3.00 X 103 cm) = 7.50 X 106 cm2
Volume= 1 qt X 1000 cm3 = 943 cm3
1 1.06 qt
Thickness = 943 cm3
= 1.26 X 10-4 cm
7.50 X 106 cm2
4. How might this method of finding thickness be used in finding the
size of molecules(thickness)? What information would we need?
Amount(Mass), Size?(Volume), Kind?(Density of molecule)
Conclusion
Using scientific notation and the correct number of significant figures, what is the thickness of
the two types of aluminum foil?
Regular Ultra Thin: 1.1 -1.8 X 10-3cm
Regular Thin: 1.9 -2.0 X 10-3cm
Heavy:
2.1- 2.5 X 10-3cm
/32 marks
=