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MEASUREMENTFOUNDATIONS OF SCIENCE
ESSENTIAL QUESTIONS
WHAT IS A SCIENTIFIC MEASUREMENT? WHAT IS THE DIFFERENCE BETWEEN ACCURACY AND
PRECISION? WHAT IS A SYSTEMATIC METHOD OF CONVERTING
FROM ONE MEASUREMENT UNIT TO ANOTHER?
MEASUREMENT
A DETERMINATION OF THE AMOUNT OF SOMETHING
CONTAINS A NUMBER VALUE AND A UNIT
THE NUMBER IS USELESS WITHOUT A UNIT ATTACHED
TWO COMMON MEASUREMENT SYSTEMS
ENGLISH SYSTEM USED BY PEOPLE IN THE UNITED
STATES – INVOLVES UNITS SUCH AS MILES, FEET, CUPS, TEASPOONS, POUNDS, PINTS, QUARTS, GALLONS AND INCHES – lots of different relationships
INTERNATIONAL SYSTEM CALLED THE SYSTEM
INTERNATIONAL (SI UNITS) AS COINED BY THE FRENCH AND ADOPTED BY THE UNITED STATES IN 1960 – INVOLVES UNITS WHICH ARE ALL BASE 10 OR IN THE DECIMAL SYSTEM
COMPARE THE TWO SYSTEMS
ENGLISH SYSTEM – YARD STICK
1 YARD = 36 INCHES = 3 FEET SMALLEST DIVISION IS 1/32ND OF
AN INCH IN MOST CASES – A FRACTION OF AN INCH – TOUGH TO ESTIMATE THE MEASUREMENT SOMETIMES – based on fractions – ¼, 1/8, 1/16, etc.
INTERNATIONAL SYSTEM – METER STICK 1 METER = 100 CENTIMETERS = 1000
MILLIMETERS SMALLEST DIVISION IS A 1/10TH OF A
CENTIMETER OR ONE MILLIMETER – NOT A FRACTION, BUT 0.1 – EASIER TO ESTIMATE THE MEASUREMENT – based on decimals!!
COMMON SI UNITS
ACCURACY OF A MEASUREMENT
HOW CORRECT THE MEASUREMENT IS
IS IT CLOSE TO THE TARGET VALUE YOU ARE AIMING FOR?
DETERMINED BY CALCULATING A PERCENT ERROR FOR THE MEASUREMENT
CALCULATE THE PERCENT ERROR
If the density of an object is found to be 7.62 g/ml in the laboratory, what is the percent error if the reference density is 7.48 g/ml?
PRECISION OF A MEASUREMENT
HOW CLOSE THE REPEATED MEASUREMENTS ARE TO EACH OTHER
HOW CONSISTENT THE MEASUREMENTS ARE
FOR A MEASUREMENT, PRECISION IS REFLECTED IN HOW MANY SIGNIFICANT DIGITS ARE IN THE VALUE
PRECISION DEPENDS ON MEASURING INSTRUMENT
WHICH INSTRUMENT HAS BETTER PRECISION IN MEASURING THE VOLUME OF WATER?
MAKE THIS MEASUREMENT
In making a measurement, you are only allowed to estimate one digit.
All other digits are known for certain!!!
The digits known for certain and the one estimated digit are known as SIGNIFICANT DIGITS!!!!
ACTIVITY
You will be working with a partner to complete a packet in which you thoughtfully make several scientific measurements,
reporting all significant digits.
ACCURACY VS PRECISION
TIME
TWO WAYS TO THINK ABOUT TIME WHAT TIME IS IT? HOW MUCH TIME? (TIME
INTERVAL) TIME COMES IN MIXED UNITS YOU MAY NEED TO CONVERT
HOURS AND MINUTES INTO SECONDS
HOW MANY SECONDS DOES THE TIME INTERVAL REPRESENT?
DISTANCE
THE AMOUNT OF SPACE BETWEEN TWO POINTS
MEASURED IN UNITS OF LENGTH
THE METER IS THE BASIC SI UNIT
PREFIXES ARE ADDED TO REPRESENT EITHER MULTIPLES OF THE METER OR PARTS OF THE METER
1 MEGAMETER = 1,000,000 METERS
1 KILOMETER = 1000 METERS
100 CENTIMETERS = 1 METER
1000 MILLIMETERS = 1 METER
1,000,000 MICROMETERS = 1 METER
MASS
THE AMOUNT OF MATTER IN A SAMPLE
MEASURED IN THE SI UNIT OF KILOGRAM
1 MEGAGRAM = 1,000,000 GRAMS
1 KILOGRAM = 1000 GRAMS
100 CENTIGRAMS = 1 GRAM
1000 MILLIGRAMS = 1 GRAM
1,000,000 MICROGRAMS = 1 GRAM
VOLUME
THE AMOUNT OF SPACE TAKEN UP BY A SAMPLE
MEASURED IN SI UNITS OF LITERS
1 MEGALITER = 1,000,000 LITERS
1 KILOLITER = 1000 LITERS
100 CENTILITERS = 1 LITER
1000 MILLILITERS = 1 LITER
1,000,000 MICROLITERS = 1 LITER
COMPUTER LANGUAGE
METRIC PREFIXES
WHAT IS CONVENIENT IS THAT THE PREFIX INDICATES MAGNITUDE WHICH DOES NOT DEPEND UPON WHAT IS BEING MEASURED
FOR EXAMPLE, GIGA MEANS A BILLION OR 1,000,000,000 OR 109 WHETHER IT IS A GIGABYTE, GIGAGRAM, GIGASECOND, GIGALITER, OR GIGAMETER.
THE MAGNITUDE IS THE SAME, THE BASE UNIT REFLECTS WHETHER IT IS A MASS, VOLUME, TIME, COMPUTER STORAGE, OR DISTANCE MEASUREMENT.
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