Warm-up

From yesterday’s experiment: • Initial Observation: • Question: • Hypothesis: • Experiment– Variables: – Constants:

• Analysis of Data: • Conclusion (Did the data support your hypothesis?):

Graphing Relationships

Relationships

• Most students will agree that the longer they study for tests, the higher they score. In other words, test grades seem to be related to the amount of time spent studying.

Relationships

• If two variables are related, one variable depends on the other.

• One variable is called the independent variable; the other is called the dependent variable.

Relationships

• If test grades and study time are related, what is the independent variable – the test grades or the time spent studying?

Relationships

• One of the most simple types of relationships is a linear relationship. In linear relationships, the change in the dependent variable is caused by a change in the independent variable can be determined from a graph.

• In this experiment you will investigate how a graph can be used to describe the relationship between the stretch of a rubber band and the force stretching it.

Science Experiments #1

T. Trimpe 2008 http://sciencespot.net/

Read the information below and then answer the questions.

SpongeBob and Patrick love to go jellyfishing. They wondered if a new brand of jellyfish bait would help them catch more jellyfish. To test their idea, they bought a big container of bait for their next 3 trips to their top-secret fishing spot. SpongeBob fished without any bait, while Patrick used the new bait. Both of them kept track of how many jellyfish they caught in 30 minutes, which is shown in the chart.

1. Which person was the control?

2. What is the independent variable?

3. What is the dependent variable?

4. Based on the data, how would you rate the new bait?

SpongeBob Patrick

25 24

18 28

26 19

Read the information below and then answer the questions.

SpongeBob and Patrick love to go jellyfishing. They wondered if a new brand of jellyfish bait would help them catch more jellyfish. To test their idea, they bought a big container of bait for their next 3 trips to their top-secret fishing spot. SpongeBob fished without any bait, while Patrick used the new bait. Both of them kept track of how many jellyfish they caught in 30 minutes, which is shown in the chart.

1. Which person was the control?

2. What is the independent variable?

3. What is the dependent variable?

4. Based on the data, how would you rate the new bait?

SpongeBob Patrick

25 24

18 28

26 19

SpongeBob

Jellyfish Bait

Number of jellyfish caught

The bait appears to have helped a small amount, but shouldn’t be rated as a great deal. Overall Patrick caught 2 more jellyfish than SpongeBob.

Making Science Graphs and

Interpreting Data

Scientific Graphs• Most scientific graphs are made

as line graphs. There may be times when other types would be appropriate, but they are rare.

• The lines on scientific graphs are usually drawn either straight or curved. These "smoothed" lines do not have to touch all the data points, but they should at least get close to most of them. They are called best-fit lines.

• In general, scientific graphs are not drawn in connect-the-dot fashion.

Directly Proportional and Inversely Proportional Graphs

As the independent variable increases, the dependent variable increases as well.

Directly Proportional

As the independent variable increases, the dependent variable decreases.

Inversely Proportional

Predicting Data on a Graph

• Graphs are a useful tool in science. The visual characteristics of a graph make trends in data easy to see.

• One of the most valuable uses for graphs is to "predict" data that is not measured on the graph. – Extrapolate: extending the graph, along the same slope, above or below

measured data. – Interpolate: predicting data between two measured points on the graph.

How to Construct a Line Graph1. Identify the variables

a. Independent variable -Goes on the X – axis (horizontal)-Should be on the left side of a

data tableb. Dependent variable

-Goes on the Y – axis (vertical) -Should be on the right side of a data table

2. Determine the scale of the Graphc. Determine a scale (numerical value for each square)

that best fits the range of each variabled. Spread the graph to use MOST of the available space

How to Construct a Line Graph

3. Number and Label Each Axisa. This tells what the lines on your graph represent. Label each axis with appropriate units.

4. Plot the Data Pointsa. plot each data value on the graph with a dot.

5. Draw the Graph a. draw a curve or line that best fits the data points. b. Most graphs of experimental data are not drawn as

“connect the dots”.

6. Title the Grapha. Your title should clearly tell what the graph is about.b. If your graph has more than one set of data, provide a key to identify the different lines.