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: http://school.discoveryeducation.com/

sciencefaircentral/

On the brown tabs on the lower left, click virtual lab. Then, hit get started.

Click How Does Your Garden Grow Virtual Lab (Flash)