UNIT 01: Introduction to Chemistry
BCLN CHEMISTRY 11 - Rev. July, 2015
Project: Density Graphing Lab
Potential Credits:
Name: ________________
/10
Goal and Instructions:
The goal of this lab is to help you gain a better understanding of density. You will also learn a bit
more about graphing and the process of creating a best-fit line. You will be provided with mass and
volume data for both water and methanol and be asked to determine the density of those 2 liquids
from that data using a graph. Finally you will be asked to answer some questions about your results.
Data:
In order to determine the density of a given liquid you need to know
both its mass and its volume. It is difficult to measure the mass of a
liquid directly as when you pour it onto the scale it simply flows off. A
graduated cylinder (image on the right) is a device we can use to
determine the volume of a liquid. If we first weigh the graduated
cylinder while it is empty and then weigh again with liquid inside, we
can subtract these two values to determine the mass of the water for a
given volume. In this experiment the mass of the graduated cylinder
was 35.00g. This means you need to subtract 35.00g from each of the
mass values given to fill in the column on the right.
Volume of
Water
3.0 mL
5.0 mL
7.0 mL
10.0 mL
13.0 mL
15.0 mL
17.0 mL
20.0 mL
23.0 mL
25.0 mL
Mass of Water
+ Graduated
Cylinder
38.00 g
40.00 g
42.00 g
45.00 g
48.00 g
50.00 g
52.00 g
55.00 g
58.00 g
60.00 g
Mass of
Water
Volume of
Methanol
3.00 g
3.0 mL
5.0 mL
7.0 mL
10.0 mL
13.0 mL
15.0 mL
17.0 mL
20.0 mL
23.0 mL
25.0 mL
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Mass of Methanol
+ Graduated
Cylinder
37.50 g
38.90 g
40.50 g
42.80 g
45.10 g
46.90 g
48.00 g
50.60 g
52.50 g
54.00 g
Mass of
Methanol
UNIT 01: Introduction to Chemistry
BCLN CHEMISTRY 11 - Rev. July, 2015
Graphing:
Use the grid provided below to graph the data from the tables. Be sure to have your mass on the
vertical axis and your volume on the horizontal axis and label your axis For each set of data (water
and methanol) draw a best fit line. A best fit line is a straight line NOT a zig zag line that connects
all the points. A good best fit line will go through as many points as possible while at the same time
having as many points above the line as below the line. You may also create your graph in Excel or
another graphing program if you are comfortable using it.
Slope and Density:
Calculate the slope for each of the two lines you have drawn. The calculated slope is also your
calculated density for each substance. These are the experimental values you will need later.
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UNIT 01: Introduction to Chemistry
BCLN CHEMISTRY 11 - Rev. July, 2015
Questions:
1. If you had a cup full of methanol and a pool full of methanol do you think they would have the
same density or different density? Explain your reasoning.
2. If you had a cup full of methanol and a pool full of methanol do you think they would have the
same mass or different mass? Explain your reasoning.
3. Use your graph to predict the mass of 6.5 mL of methanol.
4. Use the density you calculated to determine the mass of 6.5 mL of methanol. Show your
calculation and compare your answer to the answer from question 3. Which of the two do you think
is more accurate and why?
5. Is every point exactly on your best fit lines? If not suggest some reason for this.
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UNIT 01: Introduction to Chemistry
BCLN CHEMISTRY 11 - Rev. July, 2015
6. You can calculate the density of a substance by measuring the mass and volume of a simple
sample. It is preferable however to use many samples and the graphical method. What is the
advantage of the graphical method?
7. Between volume and mass which gave a larger source of error in this experiment. Explain why.
Percentage Error:
Use the internet to determine the accepted values for the density of water and methanol and write
them below. Be sure you find a value which uses the correct units (g/mL) and is at room temperature
(near 25 oC).
Water:
Methanol:
Calculate the percent error for each liquid using the following formula. Note that the straight lines | |
mean absolute value which means if your answer comes out negative you change it to be positive.
Errors are always cited as positive percentages.
% Error = Experimental Value - Accepted Value x 100%
Accepted Value
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