Experimenting with Variables 8/25/16

Transcription

1 Experimenting with Variables 8/25/16

2 Do Now

3 Why do scientists do experiments? We experiment to prove (or disprove) our hypotheses. Share: What could Allyson Felix have done to test if fruits versus vegetables would make her faster?

4 What do all experiments have in common? VARIABLES! Variables are things that can change in an experiment. When you do an experiment, you change one thing to see how it affects your results.

5 Sandwich Pop! Demo Ever seen a baking soda and vinegar volcano? HD1c What do you predict will happen when you put this mixture in a plastic bag? ARE YOU SURE?? Let s find out

6 Sandwich Pop! Demo Variables Baking Soda Bag 1-80 mg Vinegar Bag 1-20 ml Bag 2-80 mg Bag 2-40 ml Bag 3-80 mg Bag 3-80 ml

7 Sandwich Pop! Explained. 1. Each large sandwich bag has the same amount of baking soda. 2. All of the smaller sandwich bags have different amounts of vinegar. 3. When the baking soda and vinegar mix Carbon Dioxide gas is produced and the bag gets bigger with air!

8 PK & S Cont: What Are We Changing? VARIABLES Any part of an experiment that can vary. To vary means to change WHAT ARE WE NOT CHANGING? CONTROLS The normal or original group. The thing that we are not conducting the experiment on. CONSTANTS Any part of an experiment that you have to keep the same any time that you are doing the experiment.

9 Scientific Method-Controls and Variables Independent Variable-The part of the experiment that is manipulated or changed by the scientists or person performing the experiment I Control the Independent Variable You can only have ONE independent variable!

10 Scientific Method-Controls and Variables Dependent Variable- The part of the experiment that is changed or affected by the independent variable The Dependent variable Depends on what you do

11 Sandwich Pop! Demo Variables CFU/Review! Baking Soda Bag 1-80 mg Vinegar Bag 1-20 ml Bag 2-80 mg Bag 2-40 ml Bag 3-80 mg Bag 3-80 ml 1. What was the independent variable in the experiment? WHY??? How many independent variables can you have? 2. What was the control? WHY??? 3. What is the dependent variable? WHY???

12 Practice Identifying the Independent and Dependent Variables

13 Read the information below and then answer the questions. SpongeBob and Patrick love to go jelly-fishing. They wondered if a new brand of jellyfish bait would help them catch more jellyfish. To test their idea, they bought a big container of bait for their next 3 trips to their top-secret fishing spot. SpongeBob fished without any bait, while Patrick used the new bait. Both of them kept track of how many jellyfish they caught in 30 minutes, which is shown in the chart. SpongeBob Patrick Which person was the control? 2. What is the independent variable? 3. What is the dependent variable? 4. Based on the data, how would you rate the new bait?

14 Read the information below and then answer the questions. SpongeBob and Patrick love to go jelly-fishing. They wondered if a new brand of jellyfish bait would help them catch more jellyfish. To test their idea, they bought a big container of bait for their next 3 trips to their top-secret fishing spot. SpongeBob fished without any bait, while Patrick used the new bait. Both of them kept track of how many jellyfish they caught in 30 minutes, which is shown in the chart. SpongeBob Patrick Which person was the control? 2. What is the independent variable? 3. What is the dependent variable? SpongeBob Jellyfish Bait Number of jellyfish caught 4. Based on the data, how would you rate the new bait? The bait appears to have helped a small amount, but shouldn t be rated as a great deal. Overall Patrick caught 2 more jellyfish than SpongeBob.

15 Krusty Krabs Breath Mints Mr. Krabs created a secret ingredient for a breath mint that he thinks will cure the bad breath people get from eating crabby patties at the Krusty Krab. He asked 100 customers with a history of bad breath to try his new breath mint. He had fifty customers (Group A) eat a breath mint after they finished eating a crabby patty. The other fifty (Group B) also received a breath mint after they finished the sandwich, however, it was just a regular breath mint and did not have the secret ingredient. Both groups were told that they were getting the breath mint that would cure their bad breath. Two hours after eating the crabby patties, thirty customers in Group A and ten customers in Group B reported having better breath than they normally had after eating crabby patties. 1. Which people are in the control group? 2. What is the independent variable? 3. What is the dependent variable? 4. What should Mr. Krabs conclusion be? 5. Why do you think 10 people in group B reported fresher breath?

16 Sponge Bob Clean Pants Sponge Bob noticed that his favorite pants were not as clean as they used to be. His friend Sandy told him that he should try using Clean-O detergent, a new laundry soap she found at Sail-Mart. SpongeBob made sure to wash one pair of pants in plain water and another pair in water with the Clean-O detergent. After washing both pairs of pants a total of three times, the pants washed in the Clean-O detergent did not appear to be any cleaner than the pants washed in plain water. 6. What is the problem Sponge Bob wanted to investigate? 7. What is the independent variable? 8. What is the dependent variable 9. What should Sponge Bob s conclusion be?