Name ________________________ Date __________ Class



Honors Chemistry Name ________________________ Date __________ Period ___________

Lab 4: MASS, VOLUME, AND DENSITY EXPERIMENT

PURPOSE

To determine the densities of unknown metals.

BACKGROUND

An old riddle asks “Which is heavier, a pound of feathers or a pound of lead?” The question is nonsensical, of course, since a pound of feathers and a pound of lead both weigh the same, one pound. Nevertheless, there is a clearly something different about a small lead brick and a large bag of feathers, even though they weigh the same. The key to answering the riddle understands the relationship that exists between a substance’s mass and the volume it occupies. This relationship is expressed by the physical property called density. Density is defined as the ratio of a substance’s mass to the volume it occupies.

Density = mass of substance (g)

volume of substance (mL)

In this experiment, you will measure the mass and volume of several unknown materials. You will then use your data to explore the relationship between the mass and volume of the materials and to calculate their density.

After performing this lab, if someone asks you the riddle about feathers and lead, you can explain to them the difference between weight and density.

Pre-Lab Questions and Calculations: Show your work and circle your answer. Be sure to include correct sig figs and units.

1. You are given a bottle that contains 4.59 cm3 of a metallic solid. The total mass of the bottle is 35.66 g. The empty bottle weighs 14.23 g. What is the density of the solid?

2. Mercury is traded by the “flask”, a unit that has a mass of 34.5 kg. What is the volume of a flask of mercury if the density of mercury is 13.6 g/ml?

3. A gold colored ring has a mass of 18.9 grams and a volume of 1.2 mL. If the density of pure gold is 19.3 g/mL, is the ring pure gold?

4. Pumice is volcanic rock that contains many trapped air bubbles. A 225 gram sample occupied 236.6 mL. What is the density of pumice?

5. Will pumice float on water? Note, the density of water is 1 g/mL.

6. A cup of sugar has a volume of 237 mL. What is the mass of the cup of sugar if the density is 1.59g/mL?

7. Given 1 liter of water and 1 liter of gasoline, and knowing the density of water is 1.00g/ml and the density of gasoline is 0.68 g/mL, what is the difference in mass of water and gasoline? Hint: Pay attention to units

8. A sample of lead is found to have a mass of 32.6 g. A graduate cylinder contains 2.8 mL of water. After the lead sample is added to the cylinder the water level reads 5.7 mL. Calculate the density of the lead sample.

MATERIALS The balance (platform, triple beam or analytical) and the graduated cylinder are two pieces of chemistry apparatuses used in measurement. The balance is used for measuring the mass of an object and the graduated cylinder is used to measure the volume of the liquid or irregular objects.  

3 metals ( teacher will provide accepted density values)

paper towel

centigram balance

ruler

100 mL graduated cylinder

Procedure - As you perform the experiment, you will record your data in Data Table 1 and 2.

1. Determine the mass of one metal samples to the nearest 0.01 gram, using a centigram balance.

2. Find the volume of the metal sample by water displacement.

a) Fill a 100 ml graduated cylinder about half full with water.

b) Measure the volume to the best precision you are able with this instrument. Record this volume of water without the metal.

c) Place a metal in the cylinder to change the water level. Measure the volume with the metal in the water and record the measurement as “volume of water + metal”

3. Repeat step 1 and 2 for the other two metals. Dry the samples well and return them to their container

4. Record your data (mass and volume) on the board for your classmates to use for their graphing.

5. Complete Data table 1 by computing the density of each metal sample showing your work and including units.

6. Record mass and volume data collected by class in Data Table 2

7. Using the class data, plot a graph of the mass vs volume.

a. Use a whole page in your lab notebook

b. Put mass on the y axis and volume on the x axis

c. Include a title and labels for x and y axis – including units

d. You will be graphing all three metals on this graph, so represent the ordered pairs for each metal with a different symbol or color

e. Draw a best fit straight line for each metal (ignore outliers)

8. Determine the slopes of each line you have on your graph. Record the slope and your calculations in data

Table 2. Note, slope may be calculated as the change in y over the change in x .

9. Complete post lab questions.

Post lab questions

1. What does the slope of the line for each metal represent?

2. Does the density of a pure substance depend on its volume? Explain

3. What is the accepted value?

4. What is the experimental value?

5. Calculate the percent error for your density calculations (table 1) for the 3 metals. Your teacher will provide the accepted value for the density of each metal. Record them in Table 3

Percent error = experimental value – accepted value x 100 %

accepted value

6. Calculate the percent error for the density values obtained from the slopes of the lines on your graph (table 2). Record the percent error in Table 3.

7. Compare the percent errors you calculated above. Generally, the slope of the line will give a more accurate value for density than a single sample. Explain why this is true.

8. How are the error and percent error of a measurement calculated?

9. Can you identify a metal if you know its density? Explain your answer.

10. A) Do you think that determining the volumes of your metal samples by measuring their dimensions and calculating would be more accurate or less accurate than determining these volumes by water displacement. Explain.

B) Is measuring the volume of a solid always possible? Explain.

11. Based on the results of this lab, develop a hypothesis about how and why unknown substances can be

distinguished from one another by measuring their densities.

12. How would you modify this experiment to determine the density of table sugar?

13. How would you modify this experiment to determine the density of milk?

14. Write a step by step procedure to determine the density of a wood block.

|Data table 1 Team data and Calculations |

|Maintain Sig Figs |

| |Metal A |Metal B |Metal C |

|Mass (g) | | | |

|Volume of | | | |

|Water alone (ml) | | | |

|Volume of | | | |

|Water and metal (ml) | | | |

|Volume of metal (ml) | | | |

|Density of Metal (g/ml) | | | |

|Data table 2 Group Mass and Volume data of Metal Samples |

| |Metal A |Metal B |Metal C |

| |Mass |Volume |Mass |Volume |Mass |Volume |

| |(g) |(ml) |(g) |(ml) |(g) |(ml) |

|1 | | | | | | |

|2 | | | | | | |

|3 | | | | | | |

|4 | | | | | | |

|5 | | | | | | |

|6 | | | | | | |

|7 | | | | | | |

|8 | | | | | | |

|9 | | | | | | |

|10 | | | | | | |

|11 | | | | | | |

|12 | | | | | | |

|Slope off graph = | | | |

|density | | | |

|y/ x | | | |

|Data table 3 Percent Error |

| |Metal A |Metal B |Metal C |

|Accepted value | | | |

|Your Density (Table I) | | | |

|Your Density % Error | | | |

| | | | |

| | | | |

| | | | |

| | | | |

| | | | |

|Graph Density (Table 2) | | | |

|Graph Density % Error from class data | | | |

| | | | |

| | | | |

| | | | |

| | | | |

| | | | |

Name_______________________________________________

Density Lab Rubric – 79 points

_____ 1 pts Lab is entered correctly in the Table of contents

_____ 1 pts Lab entered into composition book according to basic lab rubric

_____ 16 pts Pre lab questions 1-8 are completed with proper sig figs, units, work shown, and answer circled

_____ 12 pts Physical lab and data collection completed by the student within one week of original lab date

_____ 4 pts Data table I is complete with proper sig figs and calculations shown

_____ 4 pts Data table II for class data is complete with proper sig figs and calculations shown

_____ 7 pts Graph is full page and includes axis labeled, title, 3 metals graphed and labeled

_____ 4 pts Data table III is complete with proper sig figs

_____ 24 pts Post lab questions 1-12 complete. Either the question is written and the answer is provided, or the answer restates the question as part of the answer. Example. What color is the metal? Answer option 1) What color is the metal? Silver

Answer option 2) The color of the metal is silver

_____ 2 pts Q 13 Write a hypothesis as an if then statement

_____ 2 pts Q 14 Provided detailed procedure that could be utilized as a lab procedure for a chemistry class

_____ 1 pts Lab notebook neat and legible (includes proper sized print, readable ink/lead)

_____ 1 pts Lab area left clean with all materials put back in their proper place

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