Lab 0.4: Density and Thickness of Aluminum Foil

Transcription

1 Name Block Lab 0.4: Density and Thickness of Aluminum Foil Student will be able to: Correctly use measuring instruments with accuracy Correctly apply the principles of significant figures in measurements and calculations Correctly use scientific notation in expressing the results of the calculations Objectives of the Experiment Develop the concept of density Use the density of aluminum to determine the thickness of aluminum foil Introduction An important intensive property of every substance is its density. The term intensive means that it is independent of the amount of the substance. Thus, the density of anything remains the same, no matter the shape and/or size of the sample. The density of a substance is calculated by dividing the mass of that substance by its volume. density = mass volume The S.I. units of density are kilograms per cubic meter (kg/m 3 ). Because chemists usually deal in smaller amounts, density is frequently expressed in grams per cubic centimeter (g/cm 3 ) or grams per milliliter (g/ml). Note: 1 ml = 1cm 3 For regular solids, those that have a simple formula for calculating their volume, calculating the density is straightforward: simply weigh the object and measure its dimensions. The density is calculated by dividing the mass by the volume. Each regular solid has its own formula for calculating its volume. For this experiment, the volume of a cube (VV = ll ww h) will be utilized to determine the thickness of aluminum foil. Example Calculations: Density of a Regular Solid

2 Thickness of a Material Pre-Lab Questions Do the following problems prior to performing the lab. Please express your answers in the correct number of significant figures. You must show all calculations and include units in your answer. 1. What is the volume of a block that has the dimensions of length = 8.20 cm, width = 2.25 cm, and height = 1.00 cm? 2. If the density of a substance is g/cm 3, and the volume of a sample of this substance is cm 3, what is the mass of the sample? 3. A piece of paper is known to have an area of 30.2 cm 2 and has a volume of 5.2 x 10-3 cm 3. What is the thickness of this paper?

3 Materials 3 pieces of Aluminum Foil Centimeter Ruler Triple Beam Balance Procedure 1. Obtain one set of aluminum foil pieces (3) and a ruler. 2. Using the centimeter scale, carefully measure the length and width of each piece of foil. Record the measurements in the data table. How precise can your measurements be? Think carefully before you record your results. 3. Measure the mass of each piece of foil using the triple-beam balance and record the masses in the data table. How precise can your measurements be? Think carefully before you record your results. 4. Compute the Area (A), the Volume (V), and the thickness (T) for each piece of aluminum foil. Record your answers in Data Table 2. Show all work. Your answers should have the correct number of significant figures and be expressed in scientific notation where appropriate. Data Table 1: Measurements of Length, Width, and Mass for Various Pieces of Aluminum Foil Foil Piece Length (cm) Width (cm) Mass (g) Foil #1 Foil #2 Foil #3 CALCULATIONS

4 Data Table 2: Calculated Values of Area, Volume, and Thickness for Various Pieces of Foil Foil Piece Density (g/cm 3 ) Area (cm 2 ) Volume (cm 3 ) Thickness (cm) Foil #1 Foil #2 Foil #3 Conclusions Answer all questions using complete, grammatically correct sentences. 1. Compare your answers with those of other students. How do your answers compare? Can you determine how accurate your measurements are using this type of comparison? Why or why not? 2. Obtain the accepted value for the thickness of aluminum foil from your teacher and calculate the percent error. Can you determine how accurate your measurements are using this type of comparison? Why or why not? 3. Determine three major sources of error associated with this experiment. Explain how these sources of error would affect your results. 4. How precise are your answers? Recall the definition of precision.

5 5. If you had used a very crude balance that allowed only one significant figure, how would that have affected your results? a. Area b. Volume c. Thickness Extensions Show work for any calculations necessary to solve the problems. 1. A very thin layer of gold plating was placed on a metal tray that measured cm by cm. The gold plating increased the mass of the plate by g. Calculate the thickness of the plating (The density of gold is g/cm 3 ). 2. By mistake a quart of oil was accidentally dumped into a swimming pool. The swimming pool measures 25.0 m by 30.0 m. The density of the oil was g/cm 3. How thick was the resulting oil slick? Be careful with significant figures and scientific notation. (Hint: 1.06 quarts = 1.00 liter = 1000 cm 3 ). 3. The following procedure was carried out to determine the volume of a flask. The flask was massed dry and then filled with water. If the masses of the empty flask and filled flask were g and g, respectively, and the density of water is g/cm 3, calculate the volume of the flask in cubic centimeters.