Scientific Method and Graphing

Transcription

1 Scientific Method and Graphing Objectives - Students will be able to: 1.Explain what an independent and a dependent variable are. 2.Properly label a data table and graph 3.Create a graph from a data table

2 Scientific Method Hopefully, this is a review for most of you. By the raise of hands, what are the steps to the scientific method? Scientific Method Make an observation Form an educated guess (hypothesis) Test hypothesis* Form a rule * It is ok for the test to show that your hypothesis was wrong

3 Variables We will spend most of our lab time doing experiments and trying to understand the data. Variable Something that changes How many variables are there in any given experiment? Independent variable the one variable that is deliberately changed Dependent variable the one variable that is affected by the independent variable; this is what you measure Control variable any variable that is held constant; there can be many variables in this category

4 Variables Check for understanding You re tapping the gas pedal in your car to see what happens to the A/C. Identify the independent and the dependent variable. Check for understanding You re adding water to juice to see how diluted it gets. Which are the independent, dependent, and control variables?

5 Data Tables and Graphs During the experiment, we measure how much each variable changes. At the end, we have a lot of data that needs to be put in some format that makes it easy for people to understand. For this, we use data tables and graphs. Check for understanding With your table partner, come up with at least three examples of where you see data shown in a table and three examples of where you see data shown in a graph.

6 Data Tables Data tables are set up in a certain way. Independent variable (unit) Dependent variable (unit) Each column is labeled at the top and the unit must be included. The numbers you write in the table won t have a unit next to them.

7 Lets do an example. Data Tables

8 Data Tables Data tables are set up in a certain way. Independent Variable (unit) Dependent Variable 1 (unit) Dependent Variable 2 (unit) Dependent Variable 3 (unit) A table can have more than two columns. Only the left-most column is the independent variable. All the rest are dependent variables.

9 Data Tables Lets try this. With your table partner, you will use the colored tubes and create a data table about how long it takes the bubble to travel certain distances. Each data table should have six data points. What is your independent variable? What is your dependent variable? Are there any control variables?

10 Graphs Graphs are also set up a certain way. Dependent vs. Independent Dependent Variable (unit) Units need to be included in the axis titles No arrows on axis (the data doesn t go forever) No fancy titles Independent Variable (unit)

11 Graphs Your graph should look something like this: Time (s) Time vs. Distance Next, we need to draw a trend line. This line should touch, or get close to, as many of the points as possible. Distance (cm)

12 Graphs Time (s) Time vs. Distance Distance (cm) Lastly, we need to write an equation for this line. This will follow the slope-intercept form that you learned about in Algebra. y = mx + b In science, we won t use y, m, x, or b. We will put in the actual variables and values from the graph.

13 Graphs Time vs. Distance y = mx + b 12 t = d + Time (s) t =.2d Distance (cm) 50 This is very imprecise to do by hand. We will eventually be doing this on Excel.

14 Pendulum Activity Part1: Change the mass of the pendulum to see how it affects the period of the pendulum. Use six different amounts of mass. Part2: Choose one mass for the pendulum and change the length of the string to see how it affects the period of the pendulum. Use six different string lengths.

15 Mass (g) Period (s) Pendulum Activity String Length (cm) Period (s) Time vs. Mass Time vs. String Length Time (s) Time (s) Mass (g) String Length (cm)

16 Types of Relationships Relationships tell us how variables are linked to each other. Typically, when you graph something, you ll see a trend that looks like one of the lines you graphed in math class. Direct y = x Indirect Quadratic Inverse No y = -x y = x 2 y = 1/x relationship

17 To finish up Students will be able to explain what an independent and a dependent variable are. Students will be able to explain the difference between a scientist and an engineer. Students will be able to properly label a data table and graph Students will be able to create a graph from a data table