# Units of Measurement Units of Measurement 2012 Pearson Education, Inc. SI Units Systme International dUnits A different base unit is used for each quantity. 2012 Pearson Education, Inc.

Metric System Prefixes convert the base units into units that are appropriate for the item being measured. 2012 Pearson Education, Inc. Volume The most commonly used metric units for volume are the liter (L) and the milliliter (mL).

A liter is a cube 1 decimeter (dm) long on each side. A milliliter is a cube 1 centimeter (cm) long on each side. 2012 Pearson Education, Inc. Temperature By definition temperature is a

measure of the average kinetic energy of the particles in a sample. 2012 Pearson Education, Inc. Temperature In scientific measurements, the Celsius and Kelvin scales

are most often used. The Celsius scale is based on the properties of water. 0 C is the freezing point of water. 100 C is the boiling point of water. 2012 Pearson Education, Inc. Temperature

The kelvin is the SI unit of temperature. It is based on the properties of gases. There are no negative Kelvin temperatures. K = C + 273.15 2012 Pearson Education, Inc. Temperature

The Fahrenheit scale is not used in scientific measurements. F = 9/5(C) + 32 C = 5/9(F 32) 2012 Pearson Education, Inc. Derived Units Density is a physical property of a substance. It has units (g/mL, for example) that are

derived from the units for mass and volume. m d= V 2012 Pearson Education, Inc. Uncertainty in Measurement 2012 Pearson Education, Inc.

Uncertainty in Measurements Different measuring devices have different uses and different degrees of accuracy. 2012 Pearson Education, Inc. Dimensional Analysis We use dimensional analysis to convert one quantity to another. Most commonly, dimensional analysis utilizes conversion factors (e.g., 1 in. =

2.54 cm) 1 in. 2.54 cm or 2.54 cm 2012 Pearson Education, Inc. 1 in. Dimensional Analysis Use the form of the conversion factor that

puts the sought-for unit in the numerator: Given unit desired unit given unit desired unit Conversion factor 2012 Pearson Education, Inc.

Dimensional Analysis For example, to convert 8.00 m to inches, convert m to cm convert cm to in. 8.00 m 100 cm 1 in.

1m 2.54 cm 2012 Pearson Education, Inc. 315 in.