Identifying Variables and Forming a Hypothesis Science Project 2012

Before we begin… Have your Science Project Workbook out, Turn to page 6, the Student Progress Report Fill in the following due dates: I formed a hypothesis Due 9/6/12 I identified my variables for Research Science Project Approval Form Due 9/9/12

Identifying Variables A variable is a factor that can change in an experiment In a controlled experiment, only one variable is manipulated, or changed at a time. For your Science Project, you will perform a controlled experiment and change only one variable at a time.

Types of Variables The independent variable is the variable that YOU are changing in your experiment. It is sometimes called the manipulated variable. You will only have one independent variable. Example: If your question is “What effect does the color of light have on the growth of plants?” you will be changing the color of the light. The light is your independent variable, and you are manipulating the color.

Types of Variables The dependent variable is the factor that changes as a result of the independent variable. This is the variable that you will be measuring. It is also known as the responding variable. Example: Using the same question “What effect does the color of light have on the growth of plants?”, the variable that is being measured is plant growth. Plant growth is your dependent variable. The tool used to measure it will need to be ruler with centimeters.

Controlled variables Controlled variables are also known as constants. These are the factors in an experiment that stay the same. Since only one variable is manipulated in an experiment, you will have several constants. Using the same example: What types of things will stay the same in the experiment about plants colors of light?

Your turn! Turn to page 8 in your Science Project Workbook. On this page, you will identify all of the variables about your topic. You are to have numbers 1-5 answered by 9/6/12.

Forming a Hypothesis A hypothesis is a possible explanation for a set of observations or answer to a scientific question. It must be testable! Scientists often use the IF/THEN format when writing a hypothesis. If I….(do this) then (this will happen). A good hypothesis not only states a prediction but also gives details about the experiment.

Examples Examples of good hypotheses: If I change the color of light when growing plants, then I think the plant grown with the yellow light will grow the most. If I place Mentos in different types of soda, then I predict the Diet Soda will have the strongest chemical reaction. These examples tell me the prediction as well as details about the experiment being performed.

Non-Examples Examples of hypotheses that are not acceptable: I think my design of paper airplane will fly the farthest. If I grow a plant in different lights then it will have an effect on them. If I drop Mentos in soda then it will have a reaction.

Your turn! Page 8 in your Science Project Workbook has space at the bottom for you to try writing a hypothesis using different formats. You have until 9/6/12 to have your hypothesis written on this page for approval.

Science Project Approval Form The Science Project Approval Form is found on page 9 of your workbook. Your approved hypothesis and variables are written on this page after your teacher has reviewed page 8. This page is to be filled out by you and signed by your parents by 9/9/12.