th 8 GRADE SCIENCE STRAND 1 THE NATURE OF SCIENCE NS 1.8.1 – NS 1.8.3 THE SCIENTIFIC METHOD The Scientific Method is a series of planned steps used by scientists to solve problems. These are the steps: 1. Ask a question or determine a problem. 2. Make a Hypothesis. 3. Gather data and test your hypothesis. 4. Analyze the results of your testing. 5. Draw a conclusion. BIGFOOT! A Game and Fish officer in Little Rock received a phone call from a person in northwest Arkansas, claiming he had evidence of a “Bigfoot” sighting there. The caller stated they had a plaster cast footprint, a sample of weird looking hair they found on a barbed wire fence, an actual picture of “Bigfoot”, and, they had an eye-witness. BIGFOOT Based on the data the officer gathered over the phone, he can make his HYPOTHESIS. I THINK THERE IS A “BIGFOOT” IN NORTHWEST ARKANSAS. Now what does the officer have to do? Go up there and gather the evidence. THEN… Test the evidence! ACTUAL PICTURE HAIR SAMPLE PLASTER CAST OF FOOTPRINT BIGFOOT The officer gathered these 3 pieces of data. The eyewitness lived a few miles up in the hills, so he would save him for last. He sent the picture to a photo lab to be analyzed. He sent the hair sample to a lab to be analyzed. He decided to “stake out” the area where the footprint was located. BIGFOOT He went to the area dressed in his camo, and hid in the bushes. After several hours he heard a loud THUMP! Then several seconds later another THUMP! Then another and another, it was getting closer. The officer saw a man who had a long metal pole with a metal cut out of a huge foot on the end of it. The man was slamming the foot into the ground, making footprints. BIGFOOT The officer stepped out of the bushes and confronted him. After questioning, the man finally confessed that he had a whiskey still hid in the area, and he thought that if people thought there was a bigfoot monster in the area, they would be scared and stay away so he could make his whiskey. BIGFOOT A day later, results from the hair sample and picture came back. The hair sample was that of a north American black bear. The picture was blown up 200 times, and a zipper could be seen in the back of it. BIGFOOT The officer still had his eye-witness to check out. He drove 3 miles up the old dirt road to talk to the man. BIGFOOT His dogs met him at the door! BIGFOOT When the man came out, he was drunk as a skunk, and told him he had seen bigfoot, pink elephants, and flying saucers too! BIGFOOT What at first seemed liked a good hypothesis, turned out to be false, but ONLY after testing the evidence. He now had to make his conclusion…. THERE IS NOT A BIGFOOT IN NORTHWEST ARKANSAS! VOCABULARY 1. CONTROL – In an experiment, the standard for comparison. 2. VARIABLE – Measurable factor, characteristic, or attribute of an individual or a system. 3. EMPIRICAL EVIDENCE – Data that can be detected, observed, or measured. 4. HYPOTHESIS – An “educated guess”. An explanation for a question or a problem that can be formally tested. 5. THEORY – A hypothesis that has been tested many, many times by different scientists, and the results turn out the same. VOCABULARY 6. SCIENTIFIC LAW - A descriptive generalization about how some aspect of the natural world behaves. A theory that has been tested over and over by many scientists, and is considered a “fact” of nature. 7. EXPERIMENTAL DESIGN – The design of a suitable experiment to test a hypothesis. 8. DEPENDENT VARIABLE – Factor being measured in an experiment, found on the vertical or Y-axis on a graph. 9. INDEPENDENT VARIABLE – The one factor changed in an experiment, represented on the horizontal or X-axis on a graph. VOCABULARY 10. SCIENTIFIC METHOD – A series of problem solving procedures used by scientists. EXPERIMENTS Coach Bales thinks he has come up with a “SUPER DUPER GROWTH PILL” His HYPOTHESIS (educated guess) is “I believe my super duper growth pill will increase the size of a rat over a period of time” His empirical evidence will be: 2 rats from the same litter, as close in size and weight as he can get. Each rat will get the same kind of food and water, also in same amounts. 1 rat will be given the “SUPER DUPER GROWTH PILL” GROWTH PILL EXPERIMENT Rat 1 This rat will not be given the pill. He will be the CONTROL, the standard for comparison in the experiment. GROWTH PILL EXPERIMENT Rat 2 Rat 2 will get the SUPER DUPER GROWTH PILL! This will be the VARIABLE, or the changeable factor of the experiment. It is very important in an experiment that you only test one variable at a time. GROWTH PILL EXPERIMENT Coach Bales will give each rat the same amount of food and water at the same time each day. Only rat 2 will get the growth pill. He will be compared to rat one to see if he grows more or not. After 2 weeks…….. GROWTH PILL EXPERIMENT Based on the evidence that the rat given the growth pill did in fact get bigger in size, Coach Bales can now form a theory, a hypothesis that has been tested. His theory though, must be tested many more times by many different scientists before it can be accepted as a “scientific law” or a fact of nature. SOMETIMES, EXPERIMENTS CAN BE BAD!!!!!!!!!!!!!!