1.6 The Units of Measurement

units

standard quantities used to specify measurements

metric system

the system of measurements used in most countries in which the meter is the unit of length, the kilogram is the unit of mass, and the second is the unit of time

English system

the system of units used in the United States and various other countries in which the inch is the unit of length, the pound is the unit of force, and the ounce is the unit of mass

International System of Units (SI)

the standard unit system used by scientists, based on the metric system

meter (m)

SI length unit; equivalent to 39.37 inches

kilogram (kg)

SI mass unit

mass

measure of the quantity of matter within an object

weight

measure of the gravitational pull on the matter of an object

second (s)

SI time unit

kelvin (K)

SI temperature unit and symbol

temperature

a measure of the average kinetic energy of the atoms or molecules that compose a sample of matter

heat

thermal energy transfer from hot objects to cold objects

absolute zero

0 K, coldest temperature possible, temperature at which molecular motion virtually stops

degC = (degF-32)/1.8

conversion between Celsius and Fahrenheit

K = degC+273.15

conversion between kelvin and Celsius

mole, mol

SI amount of substance unit and symbol

ampere, A

SI electric current unit and symbol

candela, cd

SI luminous intensity unit and symbol

prefix multipliers

multipliers that change the value of the unit by powers of ten

tera (T)

10^12 prefix multiplier

giga (G)

10^9 prefix multiplier

mega (M)

10^6 prefix multiplier

kilo (k)

10³ prefix multiplier

deci (d)

10^(-1) prefix multiplier

centi (c)

10^(-2) prefix multiplier

milli (m)

10^(-3) prefix multiplier

micro (µ)

10^(-6) prefix multiplier

nano (n)

10^(-9) prefix multiplier

pico (p)

10^(-12) prefix multiplier

derived unit

a unit that is a combination of other base units (e.g. m/s, m³)

volume

measure of space, any unit of length cubed

1km = 0.6214mi

conversion between kilometers and miles

1m = 39.37in = 1.094yd

conversion between meters, inches, and yards

1ft = 30.48cm

conversion between feet and centimeters

1in = 2.54cm

conversion between inches and centimeters (exact)

1kg = 2.205lb

conversion between kilograms and pounds

1lb - 453.59g

conversion between pounds and grams

1oz = 28.35g

conversion between ounces and grams

1L = 1000mL = 1000cm³

conversion between liters, milliliters, and centimeters³

1L = 1.057qt

conversion between liters and quarts

1gal = 3.785L

conversion between liters and quarts

density (d)

ratio of mass (m) to volume (V); d=m/V

intensive property

property that is independent of the amount of a given substance, often used to identify substances (e.g. density)

extensive property

property dependent on amount of the substance (e.g. mass)