I-N-D-E-P-E-N-D-E-N-T variables, dependent variables, and constants Catalyst: What is a hypertonic solution? Let’s say you put a cell in a hypotonic solution. What will happen to it?

Team Points Team 1 18 Team 2 31 Team 3 29 Team 4 25 Team 5 23

By the end of today, SWBAT… Objectives By the end of today, SWBAT… Identify independent, dependent, and controlled variables in a scientific experiment Create a model of osmosis with eggs

Experimentation Key Point #1: A proper experiment always has an independent variable, dependent variable, and constants. The purpose of an experiment is to test how changing ONE THING affects something else. Bring em in. We discussed making observations, questions (kinda), making hypotheses, lets discuss how we test our guesses to questions.

Variables Independent Variable: The thing that I change Dependent variable: The thing that is measured Remember Variables are always nouns!!! Variables NEVER have numbers in them!!! Ask your students, what was the thing I changed? What did I measure?

ONLY CHANGE ONE THING!!! Good experiments… Constant: things that we keep the same in the experiment You must keep everything but the IV constant, or your data may not be valid! Introduce web technique.

Example Let’s say we want to design an experiment to determine what causes GSP to win fights. Ask students to identify IV, DV

GSP wins fights

Determining variables from hypotheses “If Jay-Z stops cussing, he will sell fewer CDs because students like cussing.” What is the IV? “What am I changing?” What is the DV? “What am I measuring?” What are the constants? “What stays the same?” Sometimes you will have to figure out variables after reading someone’s hypothesis.

WARNING!!!! Almost everyone gets this wrong. Last semester, I had a HUUUUUUUUUUGE problem with kids confusing the STATE of the variable with the variable itself. So, I want to clear this up explicitly.

“If Jay-Z stops cussing, he will sell fewer CDs because students like cussing.” The IV is NOT “if Jay-Z stops cussing” The DV is NOT “he will sell fewer CDs” The control is NOT “students like cussing” Remember Variables are always nouns!!! Variables NEVER have numbers in them!!! Sometimes you will have to figure out variables after reading someone’s hypothesis.

How many CDs Jay-Z sells

Practice You want to know if older microwaves heat food more slowly than new ones. So, you get a bunch of microwaves, write down their ages, and time how long it takes them to boil water. IV = DV = Microwave Age time to boil water

Practice You want to know which season has the most love bugs. Every night, you record how many love bugs you find outside. IV = DV = Season/month Amount of love bugs

Practice Students of different ages were given the same puzzle to assemble. The puzzle assembly time was measured. IV = DV = Age Puzzle Assembly Time

If there are more students, then there will be more school buses. IV = DV = Amount of students Number of school buses

If the cost of beignets increases, then fewer will be sold. What depends on what? IV = DV = Cost of Beignets Amount of Beignets sold If the cost of beignets increases, then fewer will be sold.

If the Saints sign more free agents, then they will win more games. IV = Number of free agents DV = number of games won

Conclusion Key Point #1: A proper experiment always has an independent variable, dependent variable, and constants. Independent Variable: The thing that I change Dependent variable: The thing that is measured Constant: things that we keep the same in the experiment Ask your students, what was the thing I changed? What did I measure?

Egg Lab! An egg is ONE cell! Underneath the shell is a semi-permeable membrane… a cell membrane! If we put this egg into a hypertonic/hypotonic solution, osmosis will occur.

Question Will an unshelled egg increase or decrease in size after being placed overnight in a hypertonic (corn syrup) or hypotonic (water) solution?

Egg lab! Read the procedures for the egg lab Fill out the hypothesis, IV, DV, and constants at the top of your egg lab worksheet Remember… Good hypotheses are testable and educated IV is what I change DV is what I measure (it depends on the IV) Constants do not change Once you have done all of this, check in with me. If you did a good job, I will let you begin the lab.

Exit Question Mr. LY wants to see if boys are faster than girls at solving biology questions. He records how long it takes 10 boys and 10 girls to correctly solve the same homework problems. What is the independent variable? What is the dependent variable? What is at least one constant?

After you get your computer running… Go to this website: http://school.discoveryeducation.com/sciencefaircen tral/ On the brown tabs on the lower left, click virtual lab. Then, hit get started. Click How Does Your Garden Grow Virtual Lab (Flash) Segue into teacher demo: Let’s ask the question.