Scientific Method

Scientific Method

Aristotle and his contemporaries believed that all problems could be solved by thinking about them. • Sometimes this worked, other times it did not. • For example, Aristotle thought that heavy objects would fall faster than lighter ones.

Now that does seem reasonable at first. And this is how “science” was done in ancient times. • But what did Aristotle not do? • He never tested his ideas! • The world would have to wait almost 2000 years for that to happen.

Galileo Galilei • 1564-1642 AD or CE • Lived in what is today Italy • Is considered to be the first true scientist. • Why???? • Because he actually did the experiment.

Aristotle said that heavy objects fall faster than lighter ones. • So Galileo asked, “How much faster?” • So he sent students up to the top of a building and had them drop a heavy ball and a lighter one off at the same time. He had other students waiting below to measure the difference in time between the two hitting the ground.

Key Idea • When conducting an experiment, change one factor and keep everything else exactly the same. • The one thing you change is called the variable. • All the things you keep the same are called controls.

Galileo’s Experiment • What was the variable in Galileo’s experiment? • The weight of the balls. • What were some controls? • Dropped from same height. • Dropped at same time. • Balls had same shape/size.

Review

Scientific Method Steps • State the problem. • Make a hypothesis. • Conduct the experiment. • Record/analyze data. • Make a conclusion. • Report findings to others so they can repeat the experiment.

STATEMENT of PROBLEM • Question that the scientist wants to solve. • Example: Will it sink or float? ?

Hypothesis • An educated guess • a prediction • Use “If”, “then” format • We predict that if we drop a ball from a higher height, then it will bounce higher. • “If” is the independent variable. • “Then” is the dependent variable.

HYPOTHESIS • This is the educated guess that scientist makes about their experiment before they experiment. • Example: Make an educated guess if the item will sink or float and record your answer.

Materials • All of the supplies you need to test your experiment. • Example: Gather different items that will float or sink.

Observations • Use one or more of the 5 senses to gather information • A noting and recording of…. FACTS!!! • Example: There is one teacher in the room. • There are two types of observations.

Qualitative • Qualitative observation: (quality) Usually made with our senses. • Color, shape, feel, taste, sound. • Olivia is wearing a blue sweater. • The lab tabletop is smooth. • The dog’s fur is shiny.

Quantitative • Quantitative observation: (quantity) How many. Will always have a number. • Based on exact measurement. • The room is 8 meters across. • Sarah is 141-cm tall. • Sam weighs 450 Newtons.

Inferences • Logical interpretation based upon prior knowledge and experience • Based upon observations • Example: When you entered the room, you most likely inferred that the individual in the front of the room is the teacher.

Making Inferences • You are at the counter in the office to get a bus pass signed. You see a student leave the principal’s office crying and upset. We could make an inference as to why the student is upset. • Could be in trouble (ISS, OSS, expelled) • Family problems at home (sick, accident) • Student not feeling well • Student has poor grades (failing, retention)

Note the Differences • In laboratory exercises, record observations NOT inferences • Inferences may be used when writing the conclusion in your lab report. • Let’s test your observation skills…

Take a good look at this picture

Question 1 Are there cars parked on the sides of the road?

Question 2 What color is the pickup truck driving in the road?

Question 3 Any minivans around?

Question 4 What does the blue sign say?

Question 5 What's the speed limit?

Question 6 Are there any pedestrians on the road?

Answers • Yes • Blue • Yes • Yard Sale • 35 mph • No

Procedure • Step by step directions on how to test your experiment. • Example: • Fill up container with water. • Gather items to test. • Test each item one at a time placing it gently into the water.

Data/Results • Scientist needs to record data every time they test, then review the data. • Example: Record on your paper if your item floats or sinks.

Conclusion • State whether the hypothesis was proven correct or incorrect. • Example: The scientist’s hypothesis was proven correct, the cork floated in the water.

Theory • Has a very different meaning in science than in everyday life. • “The detective has a theory about who robbed the bank.” This is a guess. • When scientists use the word theory it is not used as a guess.

Theory defined • An explanation based on many observations during repeated experiments that is valid only if it is consistent with observations, makes predictions that can be tested, and is the simplest explanation. • A logical, time tested explanation for events that occur in nature.

Scientific Method