In the study of Chemistry, we encounter very large and very small numbers. For example, the size of a molecule or thin layer of molecules is very, very small and difficult to measure directly.
In order to “measure” such numbers, we often use one measured quantity and another known property to calculate the unknown value. In this experiment, we will use this approach to calculate the thickness of various types of aluminum foil, a quantity whose direct experimental determination is not possible with common laboratory equipment.
By measuring the mass of a piece of foil and by calculating its area, the thickness of the foil can be obtained from these quantities and the known density of aluminum, 2.70 g/cm3.
Pre-lab Questions
Show your work and express answers with the correct number of significant figures and proper units.
1. Find the volume of a block with the dimensions L = 9.16 cm, W = 3.65 cm, H = 1.01 cm.
2. If the density of a substance is 0.734 g/cm3 and the volume of the substance is 21.45 cm3, find its mass.
3. Determine the thickness of a rectangular piece of paper with an area of 45.3 cm2 and a volume of 7.7 X 10-3 cm3. (Hints: rewrite the formula for volume as length X width X thickness. Also, what is the formula for area?)
Procedure
1. Cut 2 rectangular pieces of regular aluminum foil and 2 rectangular pieces of heavy-duty aluminum foil. Be sure that the dimensions are at least 10 cm on each side. Record the type (e.g. Reynolds Heavy Duty, Schnucks Regular) of each piece of aluminum foil in the data table below.
Aluminum Essay
Aluminum, symbol Al, the most abundant metallic element in the earth's crust. The atomic number of aluminum is 13; the element is in group 13 (IIIa) of the periodic table.Hans Christian Orstead, Danish chemist, first isolated aluminum in 1825, using a chemical process involving potassium amalgam. Between 1827 and 1845, Friedrich Wöhler, a German chemist, improved Oersted's process by using ...
2. Using the ruler, carefully measure the length and width of each piece of foil. Record the measurements in your data table. Take care to record your measurements with the appropriate number of significant figures. Record the length and width of each piece of aluminum foil in the data table below.
3. Using a balance, find the mass of each piece of aluminum foil. Record the measurements in your data table. Take care to record your measurements with the appropriate number of significant figures. Record mass of each piece of aluminum foil in the data table below>
Foil Type |Length (Cm) |Width (CM) |Area
(CM2) |Volume (cM3) |Mass (g) |Thick-ness
(Cm)
Known Density of Aluminum = 2.70 g/cm3.
Questions
Refer to the prelab questions if needed for assistance with calculations. Show all of your work in and ORGANIZED, NEAT, and LEGIBLE fashion. Use your UNITS. Use correct number of SIGNIFICANT FIGURES. Circle your ANSWER. Use the back of this sheet if you need more room.
1. For each piece of foil, calculate its area, volume and thickness.
The density of aluminum is 2.70 g/cm3.
Remember:
• density = mass/volume
• area = length * width,
• volume = length * width * height (which you could also express as volume = area * height)
Show the formulas used in the calculations and all work.
Sheet 1 Calculations:
Sheet 2 Calculations:
Sheet 3 Calculations:
Sheet 4 Calculations:
When you have calculated these values, record them in the data table. Values should have the appropriate number of significant figures and should be expressed in scientific notation if appropriate.
2. Compare your values with those of other students, and, if possible, with the true value of thickness given on the box of aluminum foil. How accurate are your results? How accurate were your measurements? Explain.
3. How precise are your answers?
4. If you had used a balance that only allowed one significant figure, how would this affect your results for:
area?
volume?
thickness?
5. Explain how this method could be used to determine the thickness of an oil spill. What information would be needed to complete the calculations?
The Term Paper on Balance Sheet and Annual Financial Statements
The directors are responsible for the preparation and fair presentation of the annual financial statements of the Company and Group, comprising the directors’ report, the statements of financial position as at June 2013, the statements of comprehensive income, changes in equity and cash flows for the year then ended, and the notes to the financial statements, which include a summary of significant ...
6. A thin coating of gold was placed onto a tray that measured 27.75 cm by 14.25 cm. The mass of the tray increased by 0.0624 g during the process. The density of gold is 19.32 g/cm3. Calculate the thickness of the plating. Use the back of this sheet if you need more room to show complete calculations.
