Graphing Skills: Line Graphs and Laboratory Experiments
Graphing Skills: Line Graphs and Laboratory Experiments
Graphing Skills: Line Graphs and Laboratory Experiments
Graphing Skills
Line Graphs and Laboratory Experiments
In a laboratory experiment, you usually control one variable (the independent
variable) to determine its effect on another variable (the dependent variable).
Line graphs are useful for showing the relationship between variables in a labora-
tory experiment.
For example, you might perform an experiment in which you measure the tem-
perature at which a quart of water boils when salt is added to the water. In this
case, temperature is the dependent variable, and the amount of salt being added
— a total of 4 Tbsp — is the independent variable.
The independent variable is plotted on the x-axis and labeled “Salt (Tbsp.),” with
a range of 1 to 4. The dependent variable is plotted on the y-axis and is labeled
“Temperature (°F),” with a range of 212 to 224°F.
A grid has lines running horizontally from the y-axis and vertically from the x-axis.
To plot a point, you would: 1) find the x value on the x-axis; 2) follow the vertical
line from the x-axis until it intersects the horizontal line from the y-axis at the cor-
responding y value; 3) place the point at the intersection of these two lines.
The line graph below shows how the data would be graphed for the hypothetical
experiment mentioned above.
224
221
Boiling Temperature (°F)
218
215
212
0 1 2 3 4
Tablespoons of Salt
PRACTICE
Use the line graph above to answer the following questions.
1. At approximately what temperature would a quart of water with 3 Tbsp of salt
boil?
2. How many tablespoons of salt would cause the water to boil at 217.4°F?
5. Let’s say you want to conduct an experiment that measures the volume of a
gas at different temperatures. Use the data table below to create a line graph
that shows how volume is related to temperature, with temperature as the
independent variable.
Temperature (K) Gas Volume (L)
0 0.0
200 0.7
400 1.4
800 2.8
2.0 14. C
15. B
1.5
16. A
1.0 17. A
18. C
0.5
19. D
0.0 20. C
0 200 400 600 800
Temperature (°K)
Chapter Test B
Section Quizzes: 1. E
2. D
SECTION: WHAT IS EARTH SCIENCE?
3. A
1. D
4. C
2. E
5. B
3. B
6. C
4. C
7. B
5. A
8. A
6. A
9. D
7. B
10. C
8. D
11. D
9. B
12. B
10. B
13. A
14. C
15. C
16. B