Learning Goals
After completing this virtual lab, students will be able to:
- Measure the volume of a rectangular prism of metal with both a ruler and by the volume displacement method.
- Use a balance to measure the mass of objects.
- Calculate an experimental density for an object from the measured mass and volume.
References
- Introductory Chemistry (Tro, 6th Edn): Section 2.10 -OR- the equivalent section in ChemLibre
- Video Lesson on Density
- Measurement reference.pdf (<-- super helpful)
- Refer to Exp: Measurement for more measurement reference.
Lab Activities:
- Download and print the Density Report Sheets
- Follow the instructions below to complete parts 1 and 2 for your lab report
- Upload the completed report sheets and graph into Canvas by Sunday night at 11:59 PM
Instructions:
- Part 1:
- Find your metal for Part 1 by checking the Density Assignments
- Complete Part 1: Method A by following the directions for Method A and referencing the pictures below for your assigned metal.
- Complete Part 1: Method B by following the directions for Method B and referencing the video below for your assigned metal.
- Your assigned metal is for Method A and B. Only do the work for your assigned metal!!
- Be sure to read all measuring tools and state the measurements in your data sheet to the correct level of precision.
- Pay attention to sig figs in your calculations.
- Record the data, do the calculations, and answer the questions on the report sheets.
Part 1: Density of a Solid
Method A: Measuring the volume with a ruler
Use the pictures in the chart below to record the mass, length, width and height of your assigned metal rectangular prism.
Metal | Mass | length | width | height |
A | ||||
B | ||||
C | ||||
D |
Method B: Measuring the volume by volume displacement
You will be analyzing the same object, but this time you will measure the volume by volume displacement instead of using a ruler to measure its dimensions. You should record the mass of your object from the pictures in Method A, above. For the volumes, use the videos below. The initial volume of water is the measurement of water in the graduated cylinder before the metal is added. The final volume is the volume of water after the object is added. The volume of the object is the difference between the final and initial volumes of water.
Calculate the density of the object based on the data obtained in "Method B" (volume displacement). Determine what the actual metal is that you used for parts A and B, based on its color. The possible metals are:
-
-
-
-
- Brass with a density of 8.52 g/mL
- Copper with a density of 8.96 g/mL
- Iron with a density of 7.87 g/mL
- Aluminum with a density of 2.70 g/mL
-
-
-
Compare the two methods: Method A (measuring the volume with a ruler) to Method B (measure the volume by displacement in a graduated cylinder). Which density is closer to the true value? Why do you think that is?
Metal | Video of Volume being Measured by Volume Displacement |
A | https://youtu.be/lP3xBc562J4 |
B | https://youtu.be/8qXe046iXSY |
C | https://youtu.be/V3khFX9iqTM |
D | https://youtu.be/URqCUhBb_Xo |
- Part 2:
- Find the % by mass NaCl solution assigned to you by checking the Density Assignments
- YOU ARE NOT MAKING A NaCl SOLUTION. YOU ARE JUST DOING CALCULATIONS AND MAKING A GRAPH FROM THE DATA.
- Be sure to read all instructions below and in the report sheets to get Part 2 completed.
- Use the data below to complete Part 2 in the report sheets.
Part 2. Density of Mixtures of Salt and Water ("Saltwater solutions")
Each student has been assigned a sodium chloride (NaCl) solution of a certain % by mass concentration. Concentrations of percent by mass are out of a total mass of 100 g. For example: 2.5 % NaCl would be 2.5 g NaCl, 97.5 g H2O.
Watch this video for how I made the example solution, obtained a 10.00 mL sample, and measured its mass:
Calculate the masses of NaCl and water needed to make your assigned concentration. Then, use the data below to calculate the density of the four solutions given.
Concentration (% by mass) | Mass of the 10.00 mL Sample |
5.00% | 10.27 g |
10.00% | 10.71 g |
15.00% | 11.10 g |
7.50% | 10.51 g |
Once you've calculated the densities of these solutions, make a table of your data and use it make a graph of Density vs Concentration. It should have 4 data points on it.
Draw a best fit line through the data points and calculate the slope of the line using two points on the line. DO NOT USE DATA POINTS FOR THE SLOPE CALCULATION!
To calculate the slope, m: m = (y2 â y1) / (x2 â x1)
Use the straight line you drew on the graph and extrapolate to determine the density of the solution you were assigned.