Miramar College, Chemistry 151
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Graphing Guide
- Put a title at the top of the graph. The title should indicate the relationship you are graphing (e.g., "temperature vs. time", or "cooling curve for acetic acid").
- Label both axes with the quantity (e.g., time) and unit (e.g., seconds)
of the measurement. The independent variable (which, in Lab Activity #3, is
time) goes on the X-axis; the dependent variable (e.g., temperature) goes
on the Y-axis. The X-axis is the horizontal one and the Y-axis is vertical.
- Neither axis needs to contain the point (0,0), but they need to be labeled
with numbers so you can graph all of your measurements and fill up most of
the page with your graphed points. Start at an appropriate quantity just below
your lowest value and end at an appropriate quantity just above your highest
value. The "appropriate quantities" should be nice round numbers, depending
on the range of values and the available gradations of your graph paper. The
way you write the numbers on each axis should reflect the precision of your
measurements. (For example, if your thermometer reads to the nearest 0.1oC,
and your measurements were from 13.6 to 29.7oC, then your axis
labels could include 10.0, 15.0, 20.0, 25.0, and 30.0oC, with each
interval taking up about a quarter of the page.).
- Use a very small dot to identify the location of each data point. Use a small circle to help locate each dot.
- Draw a line or curve to show the general trend of your data. If you are graphing what should be a linear relationship, use a straightedge (ruler) to draw the best-fit straight line through the points. The line does not have to touch any of the points, but should have a similar number of points on each side. A curve or a few lines of varying slope may better represent some relationships. Never connect the dots with a zigzag line. The graph is meant to show a trend, not a set of points.