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?

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.

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!!!

Good experiments…  ONLY CHANGE ONE THING!!!  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!

Example  Let’s say we want to design an experiment to determine what causes GSP to win fights.

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?”

WARNING!!!! Almost everyone gets this wrong.

“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”  Remember  Variables are always nouns!!!  Variables NEVER have numbers in them!!!

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

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

Conclusion  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

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  Let’s say you want to figure out if drinking milk actually makes you taller. So you drink a glass of milk every day, and record your height every day.  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:  tral/ 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)