The Methods of Scientists

Section 1.2The Methods of Scientists1Objectives2Compare and contrast independent and dependent variables.Compare and contrast experimentation and investigation.Identify the differences between mass and weight.Explain what scientific notation is and how it is used.

Vocabulary3scientific methodshypothesisexperiment independent variabledependent variablecontrolLe Systme International dUnits (SI)scientific notation

The Scientific MethodAll scientists follow similar steps to investigate different areas of science. These steps must address the following items:Must use a specific method/steps to followMust be recordedMust be repeatable and yield the same resultsBy the scientist who originally did the workBy other scientistsMust be communicated to other scientists4The Scientific MethodThe Scientific Method is a series of problem solving steps that all scientists use to conduct experiments.Although we are going to define steps for the method, it is not a rigid approach. Variation is allowed.

5The Scientific Method6Scientific methods are used by scientists to help organize and plan their experiments and investigations.

The Nature of Scientific Investigations7Experimentation:An experiment is classified as an organized procedure that involves making observations and measurements to test a hypothesis.Hypothesis a testable explanation of a situation that can be supported or disproved by careful procedures.VariablesThe independent variable in an experiment is the factor that is changed by the experimenter.A dependent variable is a factor that is affected by changes in the independent variable.ControlsA control is used in an experiment to show that the results of an experiment are a result of the condition being tested.

The Nature of Scientific Investigations8InvestigationsAn investigation involves observation and collecting data.Analysis and ConclusionsDuring a scientific experiment, all data are carefully recorded. Once an experiment is complete, graphs, tables, and charts are commonly used to display data. These data are then analyzed so that a conclusion can be drawn.\You must summarize your results and what they mean in a written conclusion.

The Nature of Scientific Investigations9Analysis and Conclusions (cont.)Many times, a conclusion does not support the original hypothesis.In such a case, the hypothesis must be reevaluated and further research must be conducted.

The Scientific Method

10Steps of the Scientific MethodObserve/Gather Background Information on an Unexplained Phenomenon.Make a HypothesisA hypothesis is a statement about the phenomenon you have observed.This statement must be testable.You then test your hypothesis (conduct an experiment)Compare your results to your hypothesis.Draw a conclusion. Do your results support your hypothesis?Revise your hypothesis as necessary retest.Repeat revise/retest/conclude as many times as necessary until hypothesis is supported.Repeat experiment additional times to verify the hypothesis is corret.Report your results to other scientist allow them to verify your work.Your work is accepted!

11A Phenomenon What do you observe?

12What is your hypothesis?13How do you test your hypothesis?14Analysis/Conclusion15The SI System16Le Systme International dUnits (SI) is a modern version of the metric system based on a decimal system.In 1960, the SI System was a revision of the meter/kilogram/second version of the Metric System.The system has been nearly globally adopted. Three principal exceptions are Burma (Myanmar), Liberia, and the United States. The United Kingdom has officially adopted the International System of Units but not with the intention of replacing customary measures entirely.

The SI System17LengthThe SI unit for length is the meter (m).MassThe amount of matter in an object is called mass.The SI unit of mass is the kilogram (kg).WeightWeight is a measure of the gravitational force on an object.The SI unit for force is the newton (N).Time Time is the interval between two events. The SI unit for time is the second (s).Temperature Temperature is a measure of the average kinetic energy of the particles that make up a material. The SI unit for temperature is the kelvin (K). Absolute zero is the coldest possible temperature.

The SI System Base Units18MeasurementBase UnitLengthMeterMassKilogramTimeSecondTemperatureKelvinKelvin Temperature19

Although Kelvin is the SI unit, in practice we will use the Celsius ScaleDerived Units20AreaArea is the amount of surface included within a set of boundaries. The SI unit for area is square meters (m2).VolumeVolume is the amount of space occupied by an object.The SI unit for volume is cubic meters (m3).DensityDensity is the measure of the amount of matter that occupies a given space.The SI units for density are expressed in grams per cubic centimeter (g/cm3), grams per milliliter (g/mL), and kilograms per cubic meter (kg/m3).

Derived Units21Quantity MeasuredFormulaUnits in FormulaBase UnitOther Common UnitsAreaA = l x wA = m x mm2cm2VolumeVol. = l x w x hVol. = m x m x mm3cm3, mL, L1 cm3 = 1 mLDensityD=m/vD = g/cm3g/cm3kg/m3, g/mL

Other units in the SI are derived (made) by combining units:Larger/Smaller Units22The SI system uses prefixes on the base units to make the unit larger or smaller:

PrefixMeaningUseKilo-1000 times the base unitKilometers would be used to measure distance between cities.Centi-The base unit divided by 100Centimeters would be used to measure your textbook.Milli-The base unit divided by 1000Milligrams are often used for indicating the amount of a certain substance in foods or medicines.Practice23What unit would you use to:measure the distance from your house to the school?determine your mass?measure the length of 5th Block?if you were preparing a weather report?measure the mass of a paper clip?

Practice (cont.)24What unit would you use if you were: measuring the thickness of your pencil/pen?measuring the mass of a penny?writing a density?measuring the volume of this room?measuring the area of the football field?

Scientific Notation25In scientific notation, a number is expressed as a value between 1 and 10 multiplied by a power of 10.Form is M x 10NM must be > 1 and < 10N is an integerExamplesThe number of grains of sand on Earth is approximately 4,000,000,000,000,000,000,000 and would be written as 4 1021.The mass of Earth at 5,974,200,000,000,000,000,000,000 kg would be written as 5.9742 1024 kg.

Practice26The age of the Earth is approximately 3.5 billion years. If 1 billion = 1,000,000,000, what is the age of the Earth in scientific notation?

Pluto is approximately of 5,913,000,000 km from the Sun. Write this number in scientific notation.

However, should Pluto ever be near its closest point to Earth's orbit when the Earth is also near that point, the closest approach between the two would be 4.3 x 109 kilometers. Write this value as a non-scientific notation number.