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Chapter 1.4. Units of Measurement. Metric System. Units for scientific measurements Developed in France in 18 th century Unlike English system. SI Units. 1960 international agreement Preferred metric units 7 base units. Prefixes. Decimal fractions Multiples of various units
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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-
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