I NTERNATIONAL SYSTEM OF UNITS 3.2

I NTERNATIONAL SYSTEM OF UNITS Abbreviated SI (Systeme International d’Unites) A revised version of the metric system. Adopted by international agreement in SI base units, all other units are derived from these.

S I B ASE U NITS QuantitySI Base UnitSymbol LengthMeterM MassKilogramkg TemperatureKelvinK TimeSeconds Amount of SubstanceMolemol Luminous intensityCandelacd Electric CurrentAmpereA

C OMMONLY USED METRIC P REFIXES Mega (M)1 million times larger than the unit it precedes (10 6 ) Kilo (k) 1000 times larger than the unit it precedes (10 3 ) Deci (d) 10 times smaller than the unit it precedes (10 -1 ) Centi (c) 100 times smaller than the unit it precedes (10 -2 ) Milli (m) 1 million times smaller than the unit it precedes (10 -3 ) Micro (µ) 1 million times smaller than the unit it precedes (10 -6 ) Nano (n) 1000 million times smaller than the unit it precedes (10 -9 ) Pico (p) 1 trillion times smaller than the unit it precedes ( )

U NIT OF L ENGTH – METER 1 kilometer is the length of about 5 city blocks.

U NIT OF L ENGTH - METER 1 meter is the height of a doorknob from the floor

U NIT OF L ENGTH – METER 1 decimeter is the diameter of a large orange

U NIT OF L ENGTH – METER 1 centimeter is the width of shirt button

U NIT OF L ENGTH – METER 1 millimeter is the thickness of a dime

U NIT OF L ENGTH – METER 1 micrometer is the diameter of a bacterial cell

U NIT OF L ENGTH – METER 1 nanometer is the thickness of an RNA molecule

U NITS OF V OLUME -L ITER 1 liter is the same as a quart of milk

U NITS OF V OLUME - 1 MILLILETER 20 drops of water

M ASS VS. W EIGHT Mass is the amount of matter in an object and is not dependent on gravity. Weight is the measure of the gravitational pull on an object.

U NIT OF M ASS – 1 KILOGRAM About the size of a small textbook

U NITS OF M ASS - 1 GRAM Is equal to the dollar bill.

U NITS OF T EMPERATURE Temperature is a measure of how hot or cold an object is. Scientists often use the celsius scale when doing experiments. The kelvin scale is also used. K = ºC ºC = K – 273 Example: Convert 100 ºC to kelvin. 100 ºC = 373 K Example: Convert 400 K to ºC = 127 ºC

A BSOLUTE ZERO 0 K, zero kelvin Equal to ºC All motion of particles in objects cease.

U NITS OF E NERGY Energy is the capacity to do work or to produce heat. The joule (J) and the calorie (cal) are common units of energy. 1 J = cal 1 cal = J Convert 4 J to cal. 4 J x cal 1 J =0.956 cal

S ECTION R EVIEW Which 5 SI base units are commonly used in Chemistry? Which metric units are commonly used to measure length, volume, mass, temperature, and energy? How do you convert between ºC and Kelvin? What is the relationship between joules and calories? Homework: pg 79 # 18-27