The Scientific Method

Is the act of making discoveries by accident. Serendipity:

Not all discoveries in science are serendipitous. Many discoveries are a result of the scientific method.

The scientific method is an organized set of steps scientists use to solve problems. Step 1: Ask a question/ Obtain information Step 2: State problem Step 3: Form a Hypothesis Step 4: Design & Run Experiment Step 5: Analyze the Collected Data Step 6: Form a Conclusion

What happens to food that is left in an open trash can for a few days in summer?

This idea that non-living things can give rise to living organisms was called... spontaneous generation

Over time, scientists began to question the idea of spontaneous generation. They used the scientific method to disprove the idea of spontaneous generation.

In 1668, an Italian doctor named Francesco Redi set out to disprove the idea of spontaneous generation using the scientific method.

Step 1 Obtain Background Information Redi observed that maggots appeared on rotting meat a few days after flies were present.

Step 2 State the Problem Do Living Things Arise from Non-Living Things? Francesco Redi (1668) 

Step 3 State a Hypothesis Redi’s hypothesis: Maggots come from flies. Checkpoint! What is a hypothesis? An educated guess Your hypothesis:

Redi’s Experimental Design… Redi put meat into three separate jars. Jar 1 was sealed Jar 2 was covered with netting Jar 3 was left open Jar 1 Jar 2Jar 3

Design & Run a Controlled Experiment Factors in an experiment that can change are called... In a controlled experiment, only one variable changes. All others remain constant. Step 4 Ex: time, temp. amount of material used, type of material used variables

The variable that is purposely changed is the manipulated variable (independent variable) What I change in the experiment. It is important to have only 1 manipulated variable. -This value is plotted on the x-axis The variable that responds to this change is the responding variable (dependent variable) What is being measured… -This value is plotted on the Y-axis. The variables that do not change are called the control.

What are the controls of Redi’s experiment? What is the manipulated variable? What is the responding variable?

Step 5 written data table graph Collect & Analyze Data

Jar 3 Left open Maggots developed Flies were observed laying eggs on the meat in the open jar Jar 2 Covered with netting. Maggots appeared on the netting. Flies were observed laying eggs on the netting How would you analyze Redi’s results? Jar 1 Sealed No maggots developed Redi’s Results

What was Redi’s hypothesis? Step 6 State Your Conclusion Go back and answer your hypothesis Maggots come from flies (not meat). What was his conclusion? Maggots come from flies (not meat)

Modify your hypothesis and repeat the experiment What if your conclusion does not agree with your hypothesis?

Repeat the experiment to make sure you get the same results What if your conclusion does agree with your hypothesis?

A theory is a hypothesis that is well-supported after numerous experimental trials. Can you think of some theories? Big Bang theory Theory of evolution

After many years of acceptance, a theory becomes a... Can you think of some laws? Law of gravity Law of supply & demand Law

Theory vs. Law A theory can change but… A law does not change!

**What is the scientific method?** The scientific method is an organized set of steps scientists use to solve problems.

Step 1: State the problem Step 2: Research the problem Step 3: State a hypothesis Step 4: Design & run an experiment Step 5: Analyze Results Step 6: State Conclusion **What are the steps of the scientific method?**

**What is a variable?** **What is a controlled experiment?** In a controlled experiment, only one variable changes. All others remain constant. Variables are factors in an experiment that can change.

**What is a manipulated variable?** **What is a responding variable?** The variable that is purposely changed is the manipulated variable (independent variable). The variable that responds to this change is the responding variable (dependent variable)

**What is a control?** The variables that do not change are called the control. **What is a theory?** A theory is a well-supported hypothesis that enables scientists to make predictions.

**What is a law?** After many years of acceptance, a theory becomes a law. **What is the difference between a theory and a law?** A theory can change, but a law does not change.