Units of Measurement Agenda  Review elements  Lab Reports Tuesday  Song  Notes on Units of Measurement & SN  Homework

F fluorine

O oxygen

selenium Se

N nitrogen

chlorine Cl

S sulfur

P phosphorus

Br bromine

strontium Sr

I Iodine

arsenic As

Ga gallium

aluminum Al

Percent error formula?

Units of Measurement Date:

Song

SI UNITS  International System of Units  Measurements used around the world so results are comparable.

Base Units  How would you define base units?  Basic unit of measurement

Length  Meter, m

Mass  Kilogram, kg

Amount of Substance  Mole, mol

Temperature  Kelvin, K  NO degree sign!  Absolute Temperature  no negative #  At absolute 0, all molecular motion stops  Celsius to Kelvin  o C = K  Celsius to Fahrenheit  o F = (9/5* o C) + 32

Derived Units  Define  A combination of base units

Volume m3m3m3m3  Length x width x height  Not very practical unit so we’ll use L  1 cm 3 = 1 mL  1000 L = 1 m 3

Density  Mass / volume  Kg/m 3  More practical g/mL

Pressure  Force / Area  mmHg, torr, kPa, atm

Reliability of Measurements  Accuracy: the closeness of a single measurement to its true value.  Hitting the bullseye.

 Precision: the closeness of a set of values to each other.

Measurement Exploration  Which measuring devices are more precise?

Basic Formula A * 10 exponent  A number between 1 and 10  If original number > than 1, exponent +  If original # < than 1, exponent -

Practice  3000    130    

Homework