Unit 1.5 The International System of Units Flashcards
What is the International System of Units (SI)?
– Established in 1960
– Essentially a modernized metric system
– Official system of units for science
– Imperial system is NOT part of the SI system
SI base unit for mass
– kilogram (kg)
– Will use gram (g) as the base unit in the course
SI base unit for length
metre (m)
SI base unit for time
second(s)
SI base unit for electric current
ampere (A)
SI base unit for temperature
Kelvin (K)
SI base unit for amount of substance
mole (mol)
SI base unit for luminous intensity
candela (cd)
What was the origin of the Fahrenheit temp scale?
– Developed in 1717 by Gabriel Fahrenheit
– Designated the temp of a bath of ice melting in a solution of salt as the zero point on his scale
How does the Fahrenheit temp scale work?
– The upper point is based on water’s boiling point, designated as 212°
– The melting point of ice is designated as 32°
– Degrees are based on an English tradition of using 12 divisions
What was the origin of the Celsius Scale?
– Developed in 1742 by Anders Celsius
How does the Celsius temp scale work?
– Based on the water melting + boiling points under normal atmospheric conditions
– The current scale is an inverted form of the OG scale, which was divided into 100 increments. So, the scale is AKA the Centrigrade Scale.
What was the origin of the Kelvin Scale?
– Developed in 1848 by Lord Kelvin
How does the Kelvin temp scale work?
– Uses molecular energy to define the extremes of hot and cold
– Absolute zero (0 K) corresponds to the point at which molecular energy is at a minimum
– Preferred in scientific work, though Celsius is also common
– Temps measured on the Kelvin scale are K, not °K
What is the difference between water’s freezing point and boiling point on both the Celsius and Kelvin scales?
100°
Both a °C and a K are ____ the size of a °F
9/5
How are kelvin and celsius related?
– The kelvin is the same size as the celsius degree
– T (in °C) + 273 = T (in K)
– T (in K) - 273 = T (in °C)
Celsius absolute zero, freezing point, boiling point
– -273°C
– 0°C
– 100°C
Kelvin absolute zero, freezing point, boiling point
– 0 K
– 273 K
– 373 K
How are Fahrenheit and Celsius related?
– The only temp for which the numerical value is the same for both scales is: 40°C and -40°F
– °C = 5/9(°F - 32)
– °F = 9/5(°C + 32)
What are derived units?
– Any units that require math.
– A unit of measurement derived from the seven SI base units.
Why would scientists assign a new derived unit in the place of base units?
To reduce inconvenience and clutter of the consistent base unit usage
SI derived unit for mass
Name: tonne
Symbol: t
Written w/ base units: 1 * 10^6 g
SI derived unit for volume
Name: litre
Symbol: L
Written w/ base units: 1 * 10^-3 m^3
SI derived unit for force
Name: Newton
Symbol: N
Written w/ base units: kg*m/s^2
SI derived unit for energy
Name: joule
Symbol: J
Written w/ base units: N*m or kg/ms^2
SI derived unit for pressure
Name: pascal
Symbol: Pa
Written w/ base units: N/m^2 or kg/ms^2
What are prefixes and its purpose?
– Placed in front of a base unit and represent a multiplying factor
– Allows for expression of large and small quantities
What is the prefix giga?
– G
– 10^9 or 1,000,000,000
What is the prefix mega?
– M
– 10^6 or 1,000,000
What is the prefix kilo?
– k
– 10^3 or 1000
What is the prefix hecto?
– h
– 10^2 or 100
What is the prefix deka?
– da
– 10^1 or 10
What is the prefix deci?
– d
– 10^-1 or 0.1
What is the prefix centi?
– c
– 10^-2 or 0.01
What is the prefix milli?
– m
– 10^-3 or 0.001
What is the prefix micro?
– μ
– 10^-6 or 0.000 001
What is the prefix nano?
– n
– 10^-9 or 0.000 000 001
What is the acronym for metric conversions?
kats hate dogs __ dogs chase mice
Why did so many of the world adopt the metric system?
