Pre Laboratory Assignment Density Of Liquids And Solids In Lake

Density

Density is defined as the mass per unit volume of a substance, and it is a physical property of matter. A physical property can be measured without changing the chemical identity of the substance. Since pure substances have unique density values, measuring the density of a substance can help identify that substance. Density is determined by dividing the mass of a substance by its volume:

\[Density = \frac{Mass}{Volume}\]

The units of density are commonly expressed as g/cm3 for solids, g/mL for liquids, and g/L for gases.

Density is also an intensive property of matter. This means that the value of density is independent of the quantity of matter present. For example, the density of a gold coin and a gold statue are the same, even though the gold statue consists of the greater quantity of gold. This is in contrast to extensive properties, like volume (the amount of space occupied by matter), which depend of the quantity of mater present. The more matter present, the larger the volume.

In Part A of this lab, the mass and volume of distilled water will be measured in order to determine the density of water. Measurements will be performed on three samples of water to improve precision and accuracy. Mass will be measured with an electronic balance, in grams (g), and volume will be measured directly with a graduated cylinder, in milliliters (mL). Recall that when measuring liquid volumes, the graduated scale must be read from the lowest point of the curved surface of the liquid (the meniscus).

The accuracy of the experimentally determined density of water will then be evaluated by comparison to the true, accepted density of water.

Measuring the Volume of a Liquid

The graduated cylinder markings are every 1-milliliter. When read from the lowest point of the meniscus, the correct reading is 30.0 mL. The first 2 digits 30.0 are known exactly. The last digit 30.0 is uncertain. Even though it is a zero, it is significant and must be recorded.

In Part B of this lab, the density of aluminum will be determined using aluminum pellets. Again, mass will be measured using an electronic balance, in grams (g). However, since the pellets have irregular shapes, their volume must be measured indirectly using the technique of water displacement (also known as Archimedes Principle). This is because the volume of water that the solid displaces when it is immersed in the water is the same as the volume of the solid itself. The accuracy of this experimentally determined density will also be evaluated by comparison to the true, accepted density of aluminum.

Measuring the Volume of an Irregularly Shaped Solid

\[\text{Volume water displaced} = \text{Final volume } – \text{Initial volume}\]

\[\text{Volume water displaced} = \text{Volume of solid}\]

Note that 1 mL = 1 cm3.

The density of aluminum will then be used in an applied problem to determine the thickness of a piece of aluminum foil. The piece of foil used can be considered to be a very flat rectangular box, where

\[\text{Volume of foil} = length \times width \times thickness\]

The foil volume can be obtained from the measured mass of the foil and the density of aluminum. Thus, if the length and width of the foil rectangle are measured, then the foil’s thickness may be calculated.

Density and Graphical Analysis

Laboratory investigations involve collecting data, which is often numeric. One common method of interpreting data is graphical analysis.

In Part C of this lab, the mass and volume of several cylindrical pieces of an unknown solid material will be measured. Once again mass will be obtained using an electronic balance, in grams (g). But since the cylinders are regularly-shaped solids, their volumes (in cubic centimeters, cm3) will be calculated from their measured dimensions by using the appropriate volume formula:

\[\text{Volume of a cylinder} = 2 \pi r h\]

\[h = \text{cylinder height or length}\]

\[r = \text{cylinder radius } = \frac{1}{2} \text{ the diameter}\]

Each pair of mass and volume values will then be plotted on graph paper as a scatter plot, with mass plotted on the y-axis and volume plotted on the x-axis. Since the plotted data generate (or at least approximate) a straight line, a “best-fit line” can be added to the graph. A best-fit line is a single line that comes as close as possible to all the plotted points.

The equation of this best-fit line will have the familiar form \(y = mx + b\), where \(m\) represents the slope of the line, and \(b\) represents the y-intercept. This is illustrated in the figure below.

Best-fit line equation:

\[y = mx + b\]

\[b = y\text{-intercept}\]

\[m = \text{slope}\]

The y-intercept (\(b\)) is the point on the y-axis where the line crosses the axis. In this experiment, the value of \(b\) should be equal to zero. This is because if there is no mass, the volume must also be zero. However, note that your best-fit line might not pass exactly through the origin (0,0) due to experimental error – but it should be quite close.

The slope of the line (\(m\)) is the change in the y-axis values divided by the change in x-axis values (or, rise over run):

\[m = \frac{ \Delta y}{ \Delta x}\]

\[= \frac{y_1 − y_2}{x_1−x_2}\]

Since \( \Delta y\) is really the change in mass (\(\Delta \text{mass}\)), and \(\Delta x\) is really the change in volume (\( \Delta \text{volume}\)), this means that the slope of the best-fit line yields the density of the unknown material:

\[m = \frac{\Delta y}{\Delta x} = \frac{\Delta \text{mass}}{ \Delta \text{volume}} = \text{density}\]

Once the density is determined in this manner, it will be used to identify the unknown material analyzed.

Procedure

Materials and Equipment

100-mL graduated cylinder, metric ruler*, aluminum pellets, small beaker, aluminum foil, thermometer, electronic balance, distilled water, tube of unknown solid cylinders* and graph paper.

Safety

Be especially careful when adding the aluminum to your graduated cylinder, as the glass could break. Tilt the graduated cylinder and allow the pellets to gently slide to the bottom.

Part A: The Density of Water
  1. Using the electronic balance, obtain the mass of your 100-mL graduated cylinder. Make sure it is dry before you weigh it.
  2. Add 20-25 mL of distilled water to the graduated cylinder. Precisely measure this volume of water. Then measure the combined mass using the electronic balance.
  3. Add another 20-25 mL of distilled water to the graduated cylinder. Again, precisely measure this volume of water, and then measure the combined mass using the electronic balance.
  4. Repeat Step 3 to obtain a third set of mass and volume measurements.
  5. Use your thermometer to record the temperature of the water in your graduated cylinder.
  6. Analysis: Subtract the mass of the empty cylinder from each combined mass measurement to obtain three mass measurements of water. Use the three sets of mass and volume measurements to calculate three density values for water. Then take the average of these three density values. Finally, look up the true density of water at the temperature used, and evaluate the accuracy of your average density value by calculating your percent error.
Part B: The Density of Aluminum and the Thickness of Foil

The Density of Aluminum

  1. Using the electronic balance, obtain the mass of a clean, dry small beaker.
  2. Obtain a sample of aluminum from your instructor. Transfer all the pellets to the beaker, and measure the mass of the beaker and pellets.
  3. Pour 30-35 mL of water into your 100-mL graduated cylinder. Precisely measure this volume.
  4. Carefully add all the aluminum pellets to the water, making sure not to lose any water to splashing. Also make sure that the pellets are all completely immersed in the water. Measure the new volume of the water plus the pellets.
  5. When finished, retrieve and dry the aluminum pellets and return them to your instructor.
  6. Analysis: Use your measured mass and volume (obtained via water displacement) of the aluminum pellets to calculate the density of aluminum. Then look up the true density of aluminum and evaluate your accuracy by calculating your percent error.

The Thickness of Aluminum Foil

  1. Now obtain a rectangular piece of aluminum foil from your instructor. Use the ruler to measure the length and width of the piece of foil.
  2. Measure the mass of the foil using the electronic balance.
  3. When finished, return the foil to your instructor and the ruler to the stockroom.
  4. Analysis: Use these measurements along with the density of aluminum to calculate the thickness of the foil.
Part C: Graphical Analysis of Mass and Volume Data of an Unknown Solid
  1. Check out a ruler from the stockroom and obtain a tube containing cylindrical pieces of an unknown solid material from your instructor. Record the ID Code of the unknown solid on your report form.
  2. Using the ruler, measure the dimensions (diameter and height) of each cylindrical object. Start with the smallest object first and progress in order of increasing object size.
  3. Measure the mass of each cylindrical object using an electronic balance. Again, start with the smallest object first and progress in order of increasing object size.
  4. Replace all the objects in the tube and return the tube to your instructor.
  5. Analysis: Use the measured dimensions to calculate the volume of each solid object. Then, on the graph paper supplied, plot the mass (Y) versus the volume (X) of each measured object. Add a best- fit line to this plot. Calculate the slope of this line, which is the density of the unknown solid. Then use this density to identify the unknown material analyzed. Your unknown material is one of the substances listed in the table below.

Substance

Density (g/cm3)

Polyvinylchloride (PVC)

1.35

Maple

0.77

Acrylic

1.16

Polytetrafluoroethylene (Teflon)

2.20

Polypropylene

0.90

Aluminum

2.71

Polyurethane

1.23 

 

Pre-laboratory Assignment: The Density of Solids and Liquids

  1. Circle the correct responses in the following statement:

Density is a physical / chemical property of matter and an intensive /extensive property of matter.

  1. What devices will you use to measure the mass and the volume of water in Part A of this lab?

 

  1. In Part B of this lab you will perform several measurements in order to determine the density of a metal.
  • Name this metal:
  • Describe the technique you will use to measure the volume of this metal.

 

  1. Consider the tabulated data collected by a student for an unknown metal sample. Use this data to calculate the density of the metal (in g/cm3). Show your work clearly.

Mass of Empty Beaker

44.656 g

Mass of Beaker and Metal sample

124.400 g

Initial volume of water in cylinder

12.7 mL

Final volume of water and Metal sample

21.6 mL

  1. In Part C of this lab, you will measure the mass, height and diameter of four cylinders composed of some unknown material.
  • Calculate the volume (in cm3) of a cylinder with a measured height of 11.76 cm and a diameter of 7.22 cm. Show your work clearly.

 

  • Each pair of mass and volume values (for each cylinder) will be plotted on a scatter plot, with mass on the y- axis and volume on the x-axis. A best-fit line will then be applied to the plotted data.
    • How will you calculate the value of the slope of this best-fit line?

 

  • How will the value of the slope help you identify the unknown material that the cylinders are made of? 

 

 

Lab Report: The Density of Liquids and Solids

Part A: The Density of Water

Experimental Data

 

1st Water Addition

2nd Water Addition

3rd Water Addition

Mass of Empty Cylinder

   

Mass of Cylinder + Water

   

Mass of Water only

   

Volume of Water

   

Density of Water

   

Average Density of Water

Temperature of Water: ______________

Data Analysis

  1. Look up the true density of water at the temperature recorded:_____________
Part B: The Density of Aluminum and the Thickness of Foil

Experimental Data

Table 1 – The Density of Aluminum

Mass of Empty Beaker

 

Mass of Beaker and Al pellets

 

Mass of Al pellets

 

Initial volume of water in cylinder

 

Final volume of water and Al pellets

 

Volume of Al pellets

 

Table 2 – The Thickness of Aluminum Foil

Mass of Al Foil

 

Length of Al Foil

 

Width of Al Foil

 

Data Analysis

  1. Use your measured mass and volume of the pellets (in Table 1) to calculate the density of aluminum, in g/cm3. Show your work, and report your answer to the correct number of significant figures.

 

 

  1. Look up the true density of aluminum at http://www.chemicool.com: _______________
  • Use this to calculate the percent error in your experimentally determined density value. Show your work.

 

 

  1. Use your measurements for the aluminum foil (in Table 2) along with the true density of aluminum to calculate the foil thickness, in cm. Show your work, and report your answer in scientific notation. Consider the foil to be a very flat rectangular box, where: \(\text{Volume of foil}= length \times width \times thickness\)

 

 

Part C: Graphical Analysis of Mass and Volume Data of an Unknown Solid

Experimental Data

ID Code of Unknown Solid:

 

Small Cylinder

Medium Cylinder

Large Cylinder

EX Large Cylinder

Mass

    

Length

    

Diameter

    

Calculated Volume

    

Show a sample calculation for volume using your measured dimensions for the small cylinder below.

 

 

Data Analysis

  1. On the graph paper supplied, plot “Mass (Y) versus Volume (X)” for all four cylinders measured. Staple your graph to this report form.

Instructions for Graphing Data

  • Use a sharpened pencil.
  • Use a ruler to draw your axes.
  • Choose axis scales that make use of the entire sheet of graph paper.
  • Clearly number and label your axes.
  • Use “X” symbols for each plotted point.
  • Draw a best-fit straight line through your data points using a ruler.
  • Give your graph an appropriate title.
  1. Choose two points on your best-fit line separated far from each other. The points chosen cannot be any of your plotted data points. Circle the two points selected on your graph, and complete the table below.
 

X Value

Y Value

Point 1

  

Point 2

  

Now calculate the slope (\(m\)) of your best-fit line using the equation: \(m = \frac{y_2-y_1}{x_2-x_1}\). Show your work, and report your result to the correct number of significant figures.

 

  1. The value of the slope obtained above in #2 yields the density of your unknown solid, in units of g/cm3. Using this value, identify your unknown solid (see Procedure, Part C, #5).
  • ID Code of Unknown:
  • Name of Unknown:
  • True Density:
  1.  You are supplied with another cylinder made of the same material. If the cylinder length is 1.83 feet, calculate the mass of this cylinder, in grams. Use the true density of the solid in this calculation, and assume that the cylinder diameter is the same as all the other cylinders you measured. Show your work.

 

 

Unformatted text preview: A modular -laboratory- 5 383 program - in - chemistry program editor: H. A. Neidig Density of Liquids and Solids prepared by H. A. Neidig, Lebanon Valley College and J. N. Spencer, Franklin and Marshall College Purpose of the Experiment Determine the density of an unknown sample of rubbing alcohol, a rubber stopper, and an unknown metal, using mass and volume measurements. Background Information One of the physical properties of matter is density. This property is dependent on the volume and the mass of a sample of matter. The relationship between density, volume, and mass is shown in Equation 1. density= mass or =53 (Eq.1) volume ' The density of a liquid or of a solution is usually re- ported in units of grams per milliliter (9 mL"). The den- sity of a solid is reported in units of grams per cubic centimeter (g cm‘3). Because 1 mL is equivalent to 1 cm3, these units are interchangeable. The experimental procedure for obtaining labora- tory data in order to calculate the density of an un- known sample ot rubbing alcohol involves two steps. One step is to measure the mass of the sample. The second step is to measure its volume. The mass of a sample of a substance is measured using a balance. If the substance is a liquid, the volume oi the sample can be measured using a piece of cali- brated glassware. For solid substances, the volume can be found by measuring the volume oi liquid dis- placed by the sample. lf the solid has a regular shape, such as a cube, its volume can be calculated using Equation 2. For other geometric shapes, appropriate equations are used to calculate their volumes. volume = length x width x thickness (Eq. 2) = cm ><cm xcm = cm3 = mL When measuring volume by displacement, begin by pouring a liquid, such as water, into a graduated cyl- inder. Measure and record the volume of water. Add the weighed sample of the solid to the water in the cylinder. Measure the combined volume of water and the sub— merged solid. The difference between these two vol- umes is the volume of the solid. In this experiment, you will use the experimentally determined mass and volume of the sample to calcu- late the density of the substance. Procedure Caution: Wear departmentally approved eye protection while doing this experiment. Copyright © 1990 by Chemical Education Resources, Inc., P.0. Box 357, 220 8. Railroad, Palmyra, Pennsylvania 17078 No part of this laboratory program may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photo- copying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Printed in the United States of America 4e Determining the Density of an Unknown Rubbing Alcohol Solution Note: Your laboratory instructor will give you di- rections for using your balance and will inform you as to the number of significant digits to the right of the decimal point to use when recording your data. Note: The following instructions pertain to a top-loading balance. ' 1. Turn the balance on by pressing the control bar. The display should show zero grams. If it does not, consult your laboratory instructor. 2. Use crucible tongs to place a container or a piece of weighing paper on the center of the bal- ance pan. 3. Press the control bar or the tare barto display the container mass. Press the tare bar to return the balance display to zero. The mass of the container subtracted from the total mass of the container and its contents is called the tare. The tare function on your balance resets the display to zero grams with the empty container on the pan. The mass of the container is retained in the memory of the balance. This amount will be subtracted when the container and contents are weighed, to display only the mass of the contents. 4. Use tongs to remove the container from the balance. Place the substance or object to be weighed in the container. 5. Use tongs to replace the container and its contents on the center of the balance pan. The mass of the substance or object alone will appear on the display. 6. Read the mass of the substance or object, us- ing the number of significant digits to the right of the decimal point specified by your laboratory instructor. 7. Use tongs to remove the container and its contents from the balance pan. 8. Place the balance in the rest position. PROP 383: Density of Liquids and Solids Note: The following instructions pertain to a centigram balance. If your centigram balance has an arrest lever, your laboratory instructor will give you additional directions regarding its use. 1. With all three sliding masses set to zero, check the balance to see whether the pointer freely swings an equal distance on either side of the zero mark. If it does not, consult your labora- tory instructor. 2. Use crucible tongs to place the container on the center of the balance pan. The pointer on the center beam will deflect upward. 3. Move the appropriate sliding masses on the beams to balance the mass of the container. See TECH 382, Transfer and Measurement of Chemicals, in this series, for additional informa- tion on the use of a centigram balance. 4. Read the positions of the masses on the beams. Calculate the mass of the container, us- ing the number of significant digits to the right of the decimal point specified by your laboratory instructor. 5. Use tongs to remove the container from the balance pan. Add the substance or object to be weighed. 6. Use tongs to replace the container and its contents on the center of the balance pan. 7. Move the appropriate sliding masses on the beams to balance the mass of the container and its contents. 8. Read the positions of the masses on the beams. Calculate the combined mass of the con- tainer and its contents. 9. Return the sliding masses to their zero posi- tions on the beams. 10. Use tongs to remove the container and its contents from the pan. Note: The numbers appearing in parentheses indicate the lines on your Data Sheet on which data should be entered. 1. Weigh a clean, dry, 10-mL graduated cylinder. Re- cord this mass on your Data Sheet (3). Caution: lsopropyl alcohol is flammable and toxic if ingested. Keep isopropyl alcohol away from open flame and heat sources. 2. Use crucible tongs to remove the graduated cylin- der from the balance. Obtain from your laboratory in- structor a bottle containing your unknown rubbing al- cohol solution. Record the code number of your unknown on your Data Sheet (1). 3. Pour 5 to 6 mL of rubbing alcohol solution from the bottle into the graduated cylinder. This amount of alco- hol is Sample #1. meniscus Figure 1 Finding the meniscus Figure 2 Using line of sight to read a meniscus Note: The following instructions pertain to read- ing a volume in a graduated cylinder. 1. Place a piece of white paper or card directly behind the cylinder at the meniscus. See Figure 1. 2. Position your head so that your eye is at the same height as the level of the liquid. If you are holding the glassware, be sure that the glassware is exactly vertical. 3. Look straight at the meniscus through the glassware so that you see only a concave line, not a concave surface. 4. Read the level of the liquid at the bottom of the meniscus, the curved surface oi the liquid. See Figure 2. 4. Read the volume of Sample #1 in the cylinder to the nearest one-tenth of a milliliter, 0.1 mL. Record this volume on your Data Sheet (4). 5. Weigh Sample #1 and the graduated cylinder, us- ing the number of significant digits to the right of the decimal point specified by your laboratory instructor. Record this combined mass on your Data Sheet (2). If you are using a top-loading balance, you will not record the combined mass but will record only the mass of Sample #1 on your Data Sheet (7). 6. Transfer the alcohol sample to a test tube. Note: In Steps 7—10, you will do a determina- tion of the volume and mass of a second sample of the alcohol solution, using Sample #2. , incorrect eye position / / / ’ (high reading) _ correct eye position approximately 85.8 mL ‘ \ incorrect eye position (low reading) 48 PROP 383: Density ()quuids and Solids 7. Pour 4 to 5 mL of alcohol solution from the test tube into the graduated cylinder. This amount of alco- hol solution is Sample #2. 8. Read the volume of Sample #2 in the graduated cylinder to the nearest 0.1 mL. Record this volume on your Data Sheet (6). 9. Weigh Sample #2 and the graduated cylinder, us- ing the number of significant digits to the right of the decimal point specified by your laboratory instructor. Record this combined mass on your Data Sheet (5). If you are using a top-loading balance, you will not re- cord the combined mass but will record only the mass of Sample #2 on your Data Sheet (9). 10. Pour Sample #2 and the alcohol solution remain- ing in the test tube into the container specified by your laboratory instructor and labeled, “Discarded Un- known Rubbing Alcohol Solutions.” Il. Determining the Density of a Rubber Stopper 11. Obtain a rubber stopper from your laboratory in- structor and record its identifying number on your Data Sheet (12). Caution: Use crucible tongs to handle the rub- ber stopper. 12. Weigh the rubber stopper, using the number of significant digits to the right of the decimal point speci- fied by your laboratory instructor. Record this mass on your Data Sheet (13). 13. Add approximately 50 to 60 mL of water to your 100-mL graduated cylinder. Read the volume of liquid in the cylinder to the nearest milliliter. Record this vol- ume on your Data Sheet (14). 14. Slightly tilt the graduated cylinder and carefully slide the rubber stopper down the inside surface of the cylinder. Avoid splashing any of the water out of the cylinder. 15. Read the volume of liquid in the graduated cylin- der to the nearest milliliter. Record this volume on your Data Sheet (15). 16. Drain the water from the graduated cylinder. Dry the stopper. Return the stopper to your laboratory instructor. III. Determining the Density of an Unknown Metal 17. Obtain an unknown metal sample from your laboratory instructor and record its identifying number on your Data Sheet (18). Caution: Use crucible tongs to handle the metal sample. 18. Wipe the sample carefully with a dampened cloth, dry thoroughly, and weigh. Record the mass on your Data Sheet (19). 19. Add 50 to 60 mL of water to your 100-mL graduated cylinder. Read the volume of liquid in the graduated cylinder to the nearest milliliter. Record this volume on your Data Sheet (20). 20. Slightly tilt the graduated cylinder and carefully slide the metal sample down the inside surface of the cylinder. Avoid splashing any of the water out of the cylinder. 21. Read the volume of the liquid in the graduated cylinder to the nearest milliliter. Record this volume on your Data Sheet (21 ). 22. Drain the water from the graduated cylinder. Dry the metal sample. Return the sample to your laboratory instructor. Calculations Do the following calculations and record the results on your Data Sheet. I. Determining the Density of an Unknown Rubbing Alcohol Solution Note: If you used a top-loading balance forthis experiment, you will not need to do Steps 1 and 3. 1. Calculate the mass of Sample #1. Subtract the mass of the graduated cylinder (3) from the mass of the graduated cylinder and Sample #1 (2). Record this mass on your Data Sheet (7). 2. Calculate the density of Sample #1. Divide the mass of Sample #1 (7) by the volume of Sample #1 (4). PROP 383: Density of Liquids and Solids 49 Record the density of Sample #1 on your Data Sheet (8). 3. Calculate the mass of Sample #2. Subtract the mass of the graduated cylinder (3) from the mass of the graduated cylinder and Sample #2 (5). Record this mass on your Data Sheet (9). 4. Calculate the density of Sample #2. Divide the mass of Sample #2 (9) by the volume of Sample #2 (6). Record the density of Sample #2 on your Data Sheet (10). 5. Calculate the mean density of your unknown rub- bing alcohol solution. Add the density of Sample #1 (8) and of Sample #2 (10), and divide by two. Record this mean density on your Data Sheet (11). ll. Determining the Density of a Rubber Stopper 6. Calculate the volume of the rubber stopper. Sub- tract the volume of the water (14) from the volume of the water and stopper (15). Record the volume of the stopper on your Data Sheet (16). 7. Calculate the density of the rubber stopper. Divide the mass of the rubber stopper (13) by the volume of the rubber stopper (16). Record this density on your Data Sheet (17). Ill. Determining the Density of an Unknown Metal 8. Calculate the volume of the metal sample. Sub- tract the volume of the water (20) from the volume of the water and metal sample (21 ). Record the volume of the unknown metal on your Data Sheet (22). 9. Calculate the density of the unknown metal. Divide the mass of the unknown metal (19) by the volume of the metal (22). Record the density on your Data Sheet (23). 10. Identify the unknown metal. Use the list of metals and their densities supplied by your laboratory instruc- tor to determine the identity of your unknown metal. Record its identity on your Data Sheet (24). PROP 383: Density of‘Liquids and Solids 5' Post-Laboratory Questions (Use the spaces provided for the answers and additional paper if necessary.) 1. The density of ice at o 00 is 0.9168 g mL‘1, and that of liquid water at 0 °C is 0.9999 9 mL“. (1) What are the volumes of 1.000 g of ice and of 1.000 g of water at 0 °C? 3. Liquid mercury has a density of 13.6 g mL‘1. Which of the following substances will float on mer- cury, and which will sink? density, 9 mL" neptunium 20.4 nickel 8.9 osmium 22.6 zinc 7.1 lead 11.4 (2) A sealed glass container with a capacity of exactly 100 mL contains 96.0 mL of liquid water at 0 ° C. If the water freezes, will the container rupture? 4. A perfect cube of aluminum metal was found to weigh 20.00 g. The density of aluminum is 2.709 mL“. What are the dimensions of the cube? 2. The volume of the nucleus of a carbon atom is about 9.9 ><10‘39 mL. The molar mass of carbon is 12.00 g mol“. What is the density of the carbon nucleus? name section 7 "Mn PROP 383: Density ofI.iquids and Solids name 7 w m — r W section Data Sheet Determining the Density of an Unknown Rubbing Alcohol Solution (1) code number of alcohol solution E mass of Sample #1 and graduated cylinder, 9 (3) mass of graduated cylinder, 9 (4) volume of Sample #1, mL (5) mass of Sample #2 and graduated cylinder, 9 (6) volume of Sample #2, mL (7) mass of Sample #1, g (8) density of Sample #1, 9 mL'1 (9) mass of Sample #2, g (10) density of Sample #2, 9 mL‘1 (11) mean density of the unknown rubbing alcohol solution, 9 mL‘1 Determining the Density of a Flubber Stopper (12) identifying number of rubber stopper (13) mass of rubber stopper, 9 (14) volume of water in graduated cylinder, mL (15) volume of water and rubber stopper in graduated cylinder, mL (16) volume of rubber stopper, mL (17) density of the rubber stopper, 9 mL‘1 date 53 54 PROP 383: Density of Liquids and Solids lll. Determining the Density of an Unknown Metal (18) identifying number of unknown metal (19) mass of metal, g (20) volume of water in graduated cylinder, mL (21) volume of water and metal in graduated cylinder, mL (22) volume of metal, mL (23) density of unknown metal, 9 mL'1 (24) identity of unknown metal Calculations (Show all your work. Use additional paper if necessary.) PROP 383: Density of Liquids and Solids 55 name Section date Pre-Laboratory Assignment 1. At 25 °C, 10.0181 g of an unknown liquid was found to have a volume of 6.75 mL. ( 1) Calculate the density of the liquid. answer (2) Which of the following liquids was the un- known? density, g mL" at 25 ° 0 water 0.9982 toluene 0.8669 chloroform 1 .4832 answer (3) If the unknown liquid had been water, what would the volume have been? (4) What mass would a 10.00-mL sample of each of the liquids in (2) have? water answer toluene answer chloroform answer 2. A stopper was found to have a mass of 5.06 9. When placed in a graduated cylinder containing 45.2 mL of water, the volume of stopper and water was found to be 49.4 mL. Calculate the density of the stopper. answer 56 PROP 383: Density of Liquids and Solids 3. A chemist was given four unidentified, water-insol- uble cubes measuring 1 x1 x1 cm and asked to ar- range these substances in order of their increasing density. These cubes were labeled A, B, C, and D. As a reference, the chemist was also given the following liq— uids. whose densities in g mL‘1 at 20 °C are given below. water 0.9982 nitromethane 1.1371 toluene 0.8669 chloroform 1.4832 The chemist added one of the four substances to one of the liquids and observed whether the substance floated or sank. By repeating this procedure with the other substances and liquids, he was able to make a series of observations about the relative densities of the substances and the liquids. Use the following se- lected observations to arrange the four unknown sub- stances in order of increasing density. Briefly defend your order. (1) Substance A sank in chloroform. (2) Substance B floated in water but sank in toluene. (3) Substance Csank in water but floated in chloroform and nitromethane. (4) Substance Dsank in nitromethane but did not sink as rapidly as Substance A did in nitromethane. least most dense dense ISBN 0-675'40-353-3 ...
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