Variables: You should learn: *About the different types of variables *How to identify them when doing your work Scientific Experiments Follow Rules. • A scientist changes one factor and observes or measures what happens. 3 Variables • The factor that is changed is known as the independent variable. • The independent variable is what you are testing!! 4 • To insure a fair test, a good experiment has only one independent variable. • As the scientist changes the independent variable, he or she observes what happens. The independent variable is the thing that someone actively changes; while the dependent variable is the thing that changes as a result. In Other Words • The scientist focuses his or her observations on the dependent variable to see how it responds to the change made to the independent variable No notes!!! The Control • The scientist makes a special effort to keep other factors constant so that they will not affect the outcome. • Those factors are called controls. 8 What is the Purpose of a Control? • Controls are NOT being tested • Controls are used for COMPARISON 9 Example of Controls & Variable • For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. 10 Example of Controls & Variable • For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. 11 What is the Independent Variable in this scenario? • What is the independent variable? • Different routes • What is the dependent variable? • Different times 12 List Your Controls • • • • • Same Same Same Same Same walker time of day shoes weather pace 13 The Bikini Bottom gang loves science class and wants to do a little research. Read the description for each experiment and use your knowledge of the scientific method to answer the following questions. Flower Power SpongeBob loves to garden and wants to grow lots of pink flowers for his pal Sandy. He bought a special Flower Power fertilizer to see if it will help plants produce more flowers. He plants 2 plants of the same size in separate containers with the same amount of potting soil. He places one plant in a sunny window and waters it every day with fertilized water. He places the other plant on a shelf in a closet and waters it with plain water every day. What did Sponge Bob do wrong in this experiment? Explain. • The following scenarios can be used for practice to identify variables and controls. 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. 1. What is the independent variable? Jelly Fish Bait 2.What is the dependent variable? Sponge Bob Patrick 25 24 18 28 26 19 Number of Jelly fish caught 3.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 Read the information below and then answer the questions • . SpongeBob 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 brand of 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. 1. What was the problem Sponge Bob wanted to investigate? 2..What is the independent variable? 3.What is the dependent variable 4. What are the controls? 1. What was the problem SpongeBob wanted to investigate? 2. What is the independent variable? 3. What is the dependent variable? 4. What are the controls Super Bubbles Patrick and SpongeBob love to blow bubbles! Patrick found some Super Bubble Soap at Sail-Mart. The ads claim that Super Bubble Soap will produce bubbles that are twice as big as bubbles made with regular bubble soap. Patrick and SpongeBob made up two samples of bubble solution. One sample was made with 5 oz. of Super Bubble Soap and 5 oz. of water, while the other was made with the same amount of water and 5 oz. of regular bubble soap. Patrick and SpongeBob used their favorite bubble wands to blow 10 different bubbles and did their best to measure the diameter of each one. The results are shown in the chart 1. What did the Super Bubble ads claim? 2. What is the independent variable? 3. What is the dependent variable? 4. Look at the results in the chart. a. Calculate the average diameter for each bubble solution. Super Bubble = ______ cm Regular Soap = ________ cm b. What should their conclusion be? 5. Are the results reliable? Why or why not?