# Units of Measurement

**Topics:**International System of Units, Temperature, Kilogram

**Pages:**4 (569 words)

**Published:**October 2, 2008

Physical QualityName of UnitAbbreviation

MassKilogramKg

LengthMeterm

TimeSecondsª (Sec)

TemperatureKelvinK

Amount of SubstanceMolemol

•Système International d’Unitès (used in the science community world wide) •Uses different base unit for quantity

Velocity m/s (two base units build velocity = derived unit) {g/sec, kg/min}

Metric System

PrefixAbbreviationMeaning

MegaM106

Kilok103

Centic10-2

Millim10-3

Microµ10-6

Nanon10-9

Picop10-12

Volume

Most common used metric u nits for volume: Liter (L), milliliter (mL), 1dm3 = 1L A liter is a cube 1 dm long on each side

1cm3 = 1mL A milliliter is a cube 1 cm long on each side

Uncertainty in Measurements

Different measuring devices have different uses and degrees of accuracy. Some examples are of these devices are:

•Graduated Cylinders

•Syringe

•Buret

•Pipet

•Volumetric Flask

Temperature

Measure of average kinetic energy of particles in a sample

•Kelvic Scale (purely scientific)

•Celsius Scale (scientific)

•Farenheit Scale (U.S. Only)

Molecules and atoms become unstable at Absolute zero.

No negative temperatures of Kelvins

Celsius scale is based on properties of water

0° is the freezing point of water

The Kelvin is the SI unit of temperature.

It is based on the properties of gases

K + °C + 273.15

The farenheit scale is not used in scientific measurements

°F = 1.8(°C) + 32

°C = 0.56 (°F-32)

Density

•Physical property of a substance d = m/v [g/mL, kg/L, kg/m3, g/cm3] •The formula for density is Mass per unit volume d = m/v

Significant Figures

•Digits that were measured (sig figs)

•When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers. •All nonzero digits are significant

•Zeros between two...

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