INTERNATIONAL SYSTEM OF UNITS3.2

INTERNATIONAL SYSTEM OF UNITS

Abbreviated SI (Systeme International d’Unites)

A revised version of the metric system.

Adopted by international agreement in 1960.

7 SI base units, all other units are derived from these.

SI BASE UNITS

Quantity SI Base Unit Symbol

Length Meter M

Mass Kilogram kg

Temperature Kelvin K

Time Second s

Amount of Substance Mole mol

Luminous intensity Candela cd

Electric Current Ampere A

COMMONLY USED METRIC PREFIXES Mega (M) 1 million times larger than the unit it

precedes (106 ) Kilo (k) 1000 times larger than the unit it precedes (103 ) Deci (d) 10 times smaller than the unit it precedes (10-1 ) Centi (c) 100 times smaller than the unit it precedes (10-

2 ) Milli (m) 1 million times smaller than the unit it precedes

(10-3) Micro (µ) 1 million times smaller than the unit it

precedes (10-6 ) Nano (n) 1000 million times smaller than the unit it

precedes (10-9 ) Pico (p) 1 trillion times smaller than the unit it precedes

(10-12 )

UNIT OF LENGTH – METER 1 kilometer is the

length of about 5 city blocks.

UNIT OF LENGTH- METER

1 meter is the height of a doorknob from the floor

UNIT OF LENGTH – METER

1 decimeter is the diameter of a large orange

UNIT OF LENGTH – METER

1 centimeter is the width of shirt button

UNIT OF LENGTH – METER

1 millimeter is the thickness of a dime

UNIT OF LENGTH – METER

1 micrometer is the diameter of a bacterial cell

UNIT OF LENGTH – METER

1 nanometer is the thickness of an RNA molecule

UNITS OF VOLUME -LITER

1 liter is the same as a quart of milk

UNITS OF VOLUME- 1 MILLILETER

20 drops of water

MASS VS. WEIGHT

Mass is the amount of matter in an object and is not dependent on gravity.

Weight is the measure of the gravitational pull on an object.

UNIT OF MASS – 1 KILOGRAM

About the size of a small textbook

UNITS OF MASS- 1 GRAM

Is equal to the dollar bill.

UNITS OF TEMPERATURE

Temperature is a measure of how hot or cold an object is.

Scientists often use the celsius scale when doing experiments.

The kelvin scale is also used. K = ºC + 273 ºC = K – 273 Example: Convert 100 ºC to kelvin. 100 ºC + 273 = 373 K Example: Convert 400 K to ºC . 400- 273= 127 ºC

ABSOLUTE ZERO

0 K, zero kelvin Equal to -273.15 ºC All motion of

particles in objects cease.

UNITS OF ENERGY

Energy is the capacity to do work or to produce heat.

The joule (J) and the calorie (cal) are common units of energy.

1 J = 0.2390 cal 1 cal = 4.184 J Convert 4 J to cal. 4 J x 0.2390 cal 1 J=0.956 cal

SECTION REVIEW

Which 5 SI base units are commonly used in Chemistry?

Which metric units are commonly used to measure length, volume, mass, temperature, and energy?

How do you convert between ºC and Kelvin? What is the relationship between joules and

calories?

Homework: pg 79 # 18-27