The Scientific Method

1. The Scientific Method The scientific method incorporates observations, hypotheses, experiments, theories, and laws.

2. Observations and Hypotheses • Scientists make observations when they note and record facts about natural phenomena. • Definition: A hypothesis is a tentative statement that proposes a possible explanation to some phenomenon or event. • Scientists try to explain their observations by devising hypotheses. • A hypothesis is useful if it accounts for what scientists observe in many situations.

3. Experiments and Variables • In order to learn more, scientists often perform experiments in which one or more of the conditions are controlled while others vary. • An important principal of an experiment is that it can be repeated numerous times. • Scientists will often use a control group to establish a baseline measure for their experiment. The control group is identical to all other items or subjects that you are examining with the exception that it does not receive the treatment or the experimental manipulation that all other items or subjects receive.

4. Experiments and Variables • The variable being manipulated or controlled in an experiment is called the independent variable. • The variable being measured or observed in the experiment is called the dependent variable. • The observations, which are recorded from an experiment, constitute data. • Finally, scientists will use the data collected to draw their conclusions about the experiment. Either the hypothesis is supported or it is not.

5. What if it doesn’t work? • When observations or experimental data do not fit the hypothesis, it must be scrapped or adjusted. • The new or refined hypothesis is then subjected to further experimental testing. • Note that while the hypothesis guides the design of new experiments, the experiments guide the rejection or refinement of the hypothesis.

6. What if it does work? • Once a hypothesis survives the test of repeated experimentation, it may be elevated to a theory. • A theory is an explanation of an event that has been supported by consistent, repeated experimental results and has therefore been accepted by the majority of scientists. • Theories can never be proven, however, they do give us the power to predict the behaviour of natural systems under circumstances that are different from those of the original observations.

7. Scientific Laws • A scientific law is a concise statement that summarizes the results of a broad variety of observations and experiments. • A law is different from a theory in that it only describes a natural phenomena – it does not attempt to explain it. • Scientific laws can often be expressed by simple mathematical relationships.

8. Theories • Darwin’s Theory of Evolution is the widely held notion that all life is related and has descended from a common ancestor. That is, complex creatures evolve from more simplistic ancestors naturally over time.In a nutshell, as random genetic mutations occur within an organism's genetic code, the beneficial mutations are preserved because they aid survival.

9. Theories • Einstein’s Theory of Special Relativity assumes that the speed of light in a vacuum is the same for all observers, regardless of their relative motion or the relative motion of the source of the light. • Consequences of special relativity include time dilation and the twin paradox, length contraction, and the famous mass energy equivalence (E = mc2).

10. Laws • Boyle’s Law states that the volume of a gas is inversely proportional the pressure exerted on it. Mathematically this looks like: PV = k or V = k / P Where P denotes pressure, V is the volume, and k is a constant.

11. Laws • Newton’s Second Law of Motion states that a body’s acceleration (a) is directly proportional the force (F ) applied to it and inversely proportional to its mass (m). a = F/m or more commonly F = ma

12. The Scientific Method In Practice • The following flowchart draws out all of the steps of the scientific method in their appropriate order. Please make sure that you know this chart well before our first test and also for our final exam.

13. Observations and Questions Gather Information Make a Hypothesis Perform Experiment Revise Hypothesis Repeat Several Times Hypothesis Supported Analyze Data Hypothesis Not Supported Draw Conclusions Communicate Results The Scientific Method Flowchart Identify The Problem

14. Observations and Questions Gather Information Make a Hypothesis Perform Experiment Revise Hypothesis Repeat Several Times Hypothesis Supported Analyze Data Hypothesis Not Supported Draw Conclusions Communicate Results The Scientific Method Example My Car Won’t Start Identify The Problem Have I bought gas lately? No I haven’t. It will start if I put gas in it. Put gas in the car. Not Applicable Yup. It started. Did it start? Cars need gas. Actually, you might want to keep this one to yourself.

15. Homework • Write a short (less than a page) description of your own example of how you used the scientific method during the in class paper helecoptor challenges. Describe as many steps as possible.