The Thickness of a Thin Aluminum Sheet

THE DENSITY AND THICKNESS OF A THIN ALUMINUM SHEET

In chemistry, we make use of large and small numbers most of the time. In addition, we must often make use of one set of measurements and known properties (such as density) to indirectly measure other quantities. One example of this type of “measurement: will be found in this experiment. The laboratory tools normally available would not be suitable for the direct measurement of the thickness of a piece of aluminum foil.

The formulas that will enable you to find the thickness of the foil are familiar to you. The volume of a rectangular object is found by using the formula V = L x W x H, where L = length, W = width, and H = height. Imagine that the regular object is a rectangular shaped piece of aluminum foil. Then the formula might be revised to V = L x W x T, where T = thickness of the foil. Going one step further, the area of the foil can be expressed as A = L x W, so the original formula for volume can be restated as V = A x T. Since this experiment involves finding the thickness, it would be better to rearrange the formula once again. Dividing both sides of the equation by A, we get the new equation T = V/A.

The next problem will be to find the volume and the area of a piece of aluminum foil. Remember that density is a property that is expressed as D=m/V. The density of aluminum is known and the mass of a piece of aluminum foil can be measured with a balance. The volume of the aluminum can then be calculated by using the rearranged equation V=m/D.

OBJECTIVES: The purpose of this lab is to accurately determine the density of aluminum foil, to correctly apply the principles of significant figures in calculating the thickness of aluminum foil and to correctly use scientific notation in expressing the results of the thickness calculation.

PART 1: DENSITY Write a procedure for determining the density of aluminum foil. Record the procedure in your lab notebook. Record all of the measurements you make in a data table in your lab notebook as well.

PART 2: THICKNESS Obtain three rectangular pieces of aluminum foil. Using a centimeter ruler, carefully measure the length and width of each piece of aluminum foil. Record your measurement. How precise can your measurements be? Think carefully before you record your results, and use the right number of significant figures.

Using a balance, find the mass of each piece of aluminum foil. Record the mass of each piece. Again, be careful to use correct significant figures. Background Information: 1. Explain density. 2. Explain how to use a conversion factor. 3. Explain how both of these concepts apply to this lab.

Calculations: 1. Using your measurements from Part 1, calculate the density of the aluminum you used.

2. For each piece of aluminum foil you used in Part 2, calculate the following: a. Area (A) b. Volume (V) c. Thickness (T) Refer to the beginning of this experiment for the formulas to be used. Show all of your work. Your answers must have the correct number of significant figures and be expressed in scientific notation where applicable.

3. Average the three results you calculated for the thickness of the thin pieces of aluminum foil.

4. Convert from thickness of aluminum foil to number of atoms of aluminum using this conversion factor (2.50 x 10-8 cm = 1 aluminum atom)

5. Convert from number of aluminum atoms to moles of aluminum atoms using the conversion factor (1 mole = 6.02 x 1023 atoms)

Conclusion:

Write a conclusion paragraph. Remember to state your results, analyze your results, and explain your sources of error. It will help you in your analysis to know that the actual thickness of aluminum foil is 1.6 x 10-3 cm (use to help with percent error).