The Scientific Method Joseph A. Castellano, Ph.D. By Joseph A. Castellano, Ph.D. TOPS of Santa Clara Valley (Teaching Opportunities for Partners in Science)

What is Science? Science is the study of natural processes called phenomena that we can see, hear or touch. Science is very broad and investigates living things such as animals and plants as well as non-living matter and energy. In this class, we study Physical Science, which includes chemistry, physics, astronomy, and other related topics such as density.

How Scientists Work The two key questions that all scientists ask are WHY and HOW. Scientists raise questions about the world around them and seek answers by making careful observations. This often leads to an initial theory or hypothesis.

The Work of Scientists Scientists conduct tests called experiments to discover why and how a process works to test the initial hypothesis. All experiments, measurements, and observations are carefully recorded in a notebook so that experimental results can be repeated and verified.

The Scientific Method Scientists use experimental results to confirm the theory or to create a new or modified theory of why and how the process works. The theory is tested by how well it fits with other theories and predicts new findings. Scientist then publish the results in a scientific journal so other scientists can repeat and verify the results to test the theory further. After many years of testing a theory, it may become so well accepted that it is recognized as a Law of Nature.

The Scientific Method Idea (Hypothesis) Observations Measurements Lab Experiments Observations Record Results – Formulate Theory

The Scientific Method Confirm and Test Theory Publish Findings Scientists Repeat & Verify Results Theory Becomes a Law of Nature New Products Developed

Scientific Measurements Scientists use the metric system in their experiments Concept of Length The standard unit of length is the meter, identified as m Another common unit of length is the centimeter or cm 1 centimeter (cm) = 1/100 meter (m) = .01 m or 1 meter (m) = 100 centimeters (cm) = 100 cm

Scientific Measurements Standard Metric Units of Length 1,000 m = 1 kilometer (km) ROADS 100 cm = 1 m METRIC RULER 10 millimeters (mm) = 1 cm METRIC RULER 1,000 microns (μ) = 1 mm MICROSCOPE

Scientific Measurements Concept of Mass The metric unit of mass is the kilogram or kg 1 kilogram (kg) = 1/1000 gram (g) = .001 g or 1 kg = 1,000 g Concept of Time The standard unit of time is the second or s

Scientific Measurements Standard Metric Units of Mass 1,000 g = 1 kg 1,000 milligrams (mg) = 1 g 1,000 micrograms (μg) = 1 mg 1,000,000 micrograms (μg) = 1 g PERSON (50 – 60 kg) EGG (45 – 50 g) GRAIN OF SAND (12 μg)

Scientific Measurements: Concept of Temperature The standard international unit for temperature is degrees Celsius, designated as C Another unit of temperature often used by scientists is Kelvin, designated as K. K = C + 273 Degrees Fahrenheit ( F) is mostly used in the United States by the general public. The conversion from F to C is: C = 5/9 ( F – 32). o o o o o o o

Scientific Measurements Accuracy & Precision (Reproducibility) Accuracy How much uncertainty does your measurement have? Half of the smallest interval marked on the tool See your metric ruler: if the true value is 10.17 centimeters and the metric ruler has millimeter marks, then you can be accurate to: Uncertainty is not about place value, so it is wrong to say + .01 mm because you can’t read 1/100 mm on the tool! + .05 cm or + .5 mm

Scientific Measurements Accuracy & Precision (Reproducibility) Precision Do you get the same number over and over? You measure the mass of a piece of steel three times and get the following results: 50.2 g 50.4 g 50.3 g The average is: (50.2 g + 50.4 g + 50.3 g) / 3 = 50.3 g so the measurements are precise to + 0.1 g Note the unit g after each number There are no naked numbers in science!

Scientific Measurements Accuracy & Precision (Reproducibility) There is no such thing as a perfect measurement so it is important to know both the accuracy (uncertainty) and precision (reproducibility) of the measurement.

Scientific Calculations Balancing of Units When making calculations always make sure the units balance. Example: A runner reaches a speed of 10 meters/second, 20 seconds after he starts. How far does he travel? D (distance) = V (velocity) x t (time) D = 10 m x 20 s = 200 m s X X The answer is 200 meters

The Importance of Science Science provides the means to improve the way of life for current and future generations of people. Scientists: Develop new instruments and surgical techniques to identify and cure diseases. Create new products that improve communications, transportation, and entertainment. Ensure the cleanliness and safety of the environment. Discover new drugs that improve and extend health.

The Importance of Science Science is at work in everyday life. An automobile’s operation involves many interrelated scientific principles including electricity, mechanics, chemistry, and physics. The calculator you use in class employs a combination of chemistry, physics, and electronic engineering. The computers in our classroom use complex mathematical principles, wireless communication technology, electronics, mechanics, chemicals, and more. Understanding science will help in your future endeavors, regardless of what they might be.