Section 5: Graphs in Science Chapter 1 Introduction to Physical Science Section 5: Graphs in Science What type of data can line graphs display? How do you determine a line of best fit or the slope of a graph? Why are line graphs powerful tools in science?

Why use Graphs? Because of their visual nature, graphs can reveal patterns or trends that words and data tables cannot. Scientists commonly use bar graphs, circle graphs, and line graphs.

The Importance of Graphs Chapter 1 Introduction to Physical Science The Importance of Graphs Line graphs are used to display data to show how one variable changes in response to another variable. In this experiment, the responding variable is the time it takes for the water to boil. The manipulated variable is the volume of water in the pot.

Open your textbooks to page 37, and let’s look at the steps of plotting a line graph. Draw the axes Label the axes Create a scale Plot the data Draw a line of best fit Add a title (horizontal axis = x-axis = independent variable, vertical axis = y-axis = dependent variable) (focus on general pattern, not connecting dots) (include both independent and dependent variables)

Why Draw a Line of Best Fit? Chapter 1 Introduction to Physical Science Why Draw a Line of Best Fit? A line of best fit emphasizes the overall trend shown by all the data taken as a whole.

Slope: The steepness of the graph line Slope = Rise = y2 - y1 Run x2 - x1 Pick any two points on the line to use the formula to find the slope of the line.

Slope Chapter 1 Introduction to Physical Science The slope of a graph line tells you how much y changes for every change in x. Slope = 25 km – 10 km = 15 km = 0.5 km/min 50 min – 20 min 30 min

Using Graphs to Identify Trends Chapter 1 Introduction to Physical Science Using Graphs to Identify Trends Line graphs are powerful tools in science because they allow you to identify trends and make predictions. This graph’s data forms a straight line, so it is linear

Using Graphs to Identify Trends Chapter 1 Introduction to Physical Science Using Graphs to Identify Trends Not all line graphs will have data that fall on a straight line. This graph is nonlinear

Here are some more nonlinear graphs:

No trend Chapter 1 Introduction to Physical Science Even nonlinear graphs with no recognizable pattern provides useful information to scientists…. It most likely means that there is no relationship between the two variables.

Why Do We Use Graphs? Graphs help us visualize numerical data. There are several different types of graphs: Bar graphs Pie graphs Line graphs

Bar Graphs Bar graphs are used to show a comparison of multiple objects.

Pie Graphs Pie graphs are used to compare the parts of a whole.

Line Graphs Line graphs are used to show the relationship between variables.

Types of Relationships (between variables) Direct: as x increases y increases Indirect: as x increases y decreases Constant: as x increases y remains the same