1.5 Graphs in Science There are many types of graphs. In Life Science last year, you may have used bar graphs or pie charts often.
In chemistry and physics, the type of graph that is used most often is the line graph. Charles Law of Gas Behavior in chemistry Distance vs time graph in physics
A line graph shows how one variable changes in response to another. Line graphs are used when the manipulated or independent variable is continuous. Continuous Independent Variable
A bar graph is used when the manipulated or independent variable is not continuous but has multiple, distinct forms.
Parts of a Line Graph X axis Y axis Scale Title X axis label Y axis label Data points Line of best fit Key (if multiple sets of data points are on the same graph) The Effect of Time on Ice Sheet Area
Steps in Creating a Line Graph 1. Draw the axes. ;)
3. Create a Scale Choose a scale that fits your data points. Have consistent intervals. Your data points should fill most of the graph. (if the points are too close together, it is hard to see a trend. Everything looks like a line from far enough out – even the Milky Way Galaxy!) The scale does not have to start at zero.
5. Add a Title Your title should follow the format: “The Effect of (independent variable) on (dependent variable).” Capitalize all major words in the title. You do not need to capitalize words like “the” and “of”.
6. Draw a Line of Best Fit The line of best fit is a line that most closely fits a set of data points.
Why draw lines of best fit? A line of best fit can: – Help you see the overall trend – Help you to recognize outliers, or points that may not be accurate – Allow you predict results for data you have not yet collected
How to draw a line of best fit: 1.Plot all measured data points on a graph. 1.Make sure independent variable is on x axis. 2.Make sure dependent variable is on y axis. 2.Using a ruler, draw the line that deviates the least from the set of points. 3.Choose two points on the line (they do not have to be data points you measured – just any two points on the line) and use them to calculate the slope.
Trends in Graphs Linear Trend: Data points are in a straight line and a line of best fit can be applied. Say or Write: “As (independent variable) increases/decreases, (dependent variable) increases/decreases.”
Example “As temperature increases, volume increases.”
Nonlinear Trends: Curves For some sets of data, drawing a curve is the best way to represent the data points. Say or Write: “As (independent variable) increases/decreases, (dependent variable) increases/decreases SHARPLY ”
Example As pressure increases, volume decreases sharply.