2 - 1 Measurement The Metric System and SI Units Converting Units Measuring Volume and Mass Density Measuring Temperature

2 - 2 SI Units Many different systems for measuring the world around us have developed over the years. People in the U.S. rely on the English System. Scientists make use of SI units so that we all are speaking the same measurement language.

2 - 3 Data, results and units Data Measurements and observations.Results Data obtained from an experiment. May be converted using known equations.Units Defines the quantities being measured. All measurements must have units. To communicate our results, we must use standard units

2 - 4 Units are important has little meaning, just a number $45,000 has some meaning - money $45,000/yr more meaning - person’s salary

2 - 5 Measurements English units. - Still commonly used in the United States. Weightounce, pound, ton Lengthinch, foot, yard, mile Volumecup, pint, quart, gallon Not often used in scientific work - Very confusing and difficult to keep track of the conversions needed.

2 - 6 Measurement English units. English units. Vary in size so you must memorize many conversion factors. Common English measures of volume 1 tablespoon=3 teaspoons 1 cup= 16 tablespoons 1 pint=2 cups 1 quart=2 pints 1 gallon=4 quarts 1 peck=2 gallons 1 bushel= 4 pecks

2 - 7 Example How many teaspoons in a barrel of oil? 1 barrel of oil= 42 gallons 1 gallon= 4quarts 1 quart= 4cups 1 cup= 16tablespoons 1 tablespoon= 3 teaspoons 1 bbl x 42 x 4 x 4 x 16 x 3 gal bbl qt gal cup qt tbl cup tsp tbl = tsp

2 - 8 Metric Units Metric Units One base unit for each type of measurement. Use a prefix to change the size of unit. Some common base units. TypeNameSymbol Massgram g Lengthmeter m Volumeliter L Timesecond s Energyjoule J Measurement

2 - 9 Metric prefixes Changing the prefix alters the size of a unit. Prefix Symbol Factor megaM kilok hectoh dekada base decid centic millim

SI units System International SI - System International Systematic subset of the metric system. Only uses certain metric units. Mass kilograms Lengthmeters Timeseconds Temperaturekelvin Amountmole Currentampere Other SI units are derived from SI base units.

Example. Metric conversion How many milligrams are in a kilogram? 1 kg=1000 g 1 g =1000 mg 1 kg x 1000 x 1000 = mg kg g mg g

Converting units Factor label method Regardless of conversion, keeping track of units makes thing come out right Must use conversion factors - The relationship between two units Canceling out units is a way of checking that your calculation is set up right!

Common conversion factors Factor EnglishFactor 1 gallon= 4 quarts 4 qt/gal 1 mile= 5280 feet5280 ft/mile 1 ton= 2000 pounds2000 lb/ton Common English to Metric conversions Factor 1 liter= quarts1.057 qt/L 1 kilogram= 2.2 pounds2.2 lb/kg 1 meter= yards1.094 yd/m 1 inch= 2.54 cm2.54 cm/inch

Example Creatinine is a substance found in blood. If an analysis of blood serum sample detected 0.58 mg of creatinine, how many micrograms were present?  = = micro mg = 580  g g 1 mg ( ) 1  g g ( )

Example A nerve impulse in the body can travel as fast as 400 feet/second. What is its speed in meters/min ? Conversions Needed 1 meter = 3.3 feet 1 minute= 60 seconds

m 400 ft 1 m 60 sec min 1 sec 3.3 ft 1 min Example m 400 ft 1 m 60 sec min 1 sec 3.3 ft 1 min ? ? =xx ? ? =xx m min....Fast 7273

Measuring volume Volume Volume - the amount of space that an object occupies. liter (L)The base metric unit is the liter (L). milliliter (mL)The common unit used in the lab is the milliliter (mL). cm 3One milliliter is exactly equal to one cm 3. SIm 3The derived SI unit for volume is the m 3 which is too large for convenient use.

Measuring mass Mass Mass - the quantity of matter in an object. Weight Weight - the effect of gravity on an object. Since the Earth’s gravity is relatively constant, we can interconvert between weight and mass. kilogram (kg) gram (g) The SI unit of mass is the kilogram (kg). However, in the lab, the gram (g) is more commonly used.

Density Density is property of a substance based on its ratio of mass to volume. Common units are g / cm 3 or g / mL. g / cm 3 Air Bone Water 1.0Urine Gold19.3Gasoline Density = Mass Volume cm 3 = mL

Example. Density calculation What is the density of 5.00 mL of a fluid if it has a mass of 5.23 grams? d = mass / volume d = 5.23 g / 5.00 mL d = 1.05 g / mL What would be the mass of 1.00 liters of this sample?

Example. Density calculation What would be the mass of 1.00 liters of the fluid sample? The density was 1.05 g/mL. density = mass / volume somass = volume x density mass = 1.00 L x 1000 x 1.05 = 1.05 x 10 3 g ml L g mL

Temperature conversion Temperature - measure of heat energy. Three common scales used Fahrenheit, Celsius and Kelvin. o F= 32 o F + ( o C) X o C = ( o F - 32 o F) K = ( o C + 273) X SI unit 5oC9oF5oC9oF 9oF5oC9oF5oC 1 K 1 o C

Example. o F to o C If it is 20 o F outside, what is it in o C ? o C = ( o F - 32 o F) 5oC5oC 9oF9oF o C = (20 o F - 32 o F) 5oC5oC 9oF9oF o C = -6.7 (two significant figures in 20 o F)