Chapter 1.4 Units of Measurement
Metric System Units for scientific measurements Developed in France in 18th century Unlike English system
SI Units 1960 international agreement Preferred metric units 7 base units
Prefixes Decimal fractions Multiples of various units Ex: milli-
Prefixes of the Metric System
Length and Mass Length SI Unit meter (m) 1 meter = 1.0936133 yd Mass SI Unit kilogram (kg) 1 kg = 2.2 lbs Unusual use of prefix
Temperature Hotness/coldness Direction of heat flow Celsius and Kelvin
Celsius Scale Everyday scale in most countries Used often in scientific studies 0 C= Freezing point of water 100 C= Boiling point of water at sea level
Fahrenheit to Celsius F = (9/5) (C) + 32 C = (5/9) (F - 32)
Kelvin Scale SI temperature scale Based on the properties of gases Zero is the lowest obtainable temperature Absolute Zero 0 K = -273.15 C
Kelvin to Celsius K = C + 273.15
Derived SI Units Formulated from base SI Units Example: speed has SI unit of m/s
Volume Derived SI Unit Cubic meters (m3) Cubic centimeters (cm3) used in chemistry cc 1 milliliter = 1 cubic centimeter 1 mL = 1 cm3
Density Density = Mass/Volume Derived SI Unit g/cm3 g/mL Always specify temperature when reporting density!! If no specification, assume 25C