Chapter 1B

Mass density

-Mass density is defined as mass per unit volume. -This is an intensive property. That is, the density of a substance does not depend on the amount of the substance present. Thus, we can use density to help identify an unknown substance. -The SI unit of density kg/m3 is somewhat cumbersome, so the units of g/cm3 or g/mL are used to express the densities of common objects. Gas densities are usually expressed ing/L -In addition to aiding in the identification of a substance, density serves as a convenient conversion factor between the mass and volume of a substance. -Using the density, we could determine the volume of 20.0 g of acetone and vice versa. At 20°C, the density of acetone is 0.7899 g/mL.

Acceleration

-Meter per second squared m/s^2

Speed,velocity

-Meter/second m/s

Temperate

-The SI base unit of thermodynamic temperature is the kelvin (K). The kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. -Temperature is the measure of the "hotness" of a body. Energy in the form of heat is transferred spontaneously from a body of higher temperature to one of lower temperature -Three temperature scales are commonly used, the Celsius, Kelvin and Fahrenheit scales.

Amount of Substance

-The SI unit for the amount of a substance is the mole (mol). -The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in exactly 0.012 kilogram of carbon 12. -When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.

Base Unit (Mass)

-The SI unit is the kilogram (kg) and it is equal to the mass of the international prototype of the kilogram, made of a platinum-iridium alloy and kept at the International Bureau of Weights and Measures. -This unit is unusual in that, unlike all the other base units, it contains a prefix. -Because multiple prefixes may not be used, in the case of the kilogram the SI prefix names are used with the unit name "gram" and the prefix symbols are used with the unit symbol "g."

Thermodynamic Temperature

kelvin (k)

Area

Length x Width The number of square units required to cover a surface. -Square Meter m^2

Measurement in Chemistry

NUMERICAL VALUE + UNIT(S) + UNCERTAINTY

Electric Current

The SI base unit is the ampere (A). The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross‑section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10 − 7 newton per meter of length.

Time

The SI base unit is the second (s). The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. Time is unusual in that it is not a decimal based measurement. 60 s = 1 minute and 60 min = 1 hour... For times shorter than one second, the normal SI prefixes are used in conjunction with the unit second, so, 10 − 12 s = 1 ps. However, the units minute, hour and day, even though they are not SI units, are accepted for use with the SI.

Luminous Intensity

The SI base unit of luminous intensity is the candela (cd). The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Volume

The amount of space an object takes up -Cubic Meter m^3 Not commonly used because its a large volume 1mL=1cm^3

Electric Current

ampere (A)

Luminous Intensity

candela (cd)

Mass

kilogram (kg)

Length

meter (m)

Amount of a substance

mole (mol)

Wave Number

reciprocal meter (m^-1)

Time

second (s)

Temperature Conversions

•K = °C +273.15 •°C = K − 273.15 •°C = 5/9 (°F − 32) •° F = 1.8 x °C + 32 •0 K is referred to as "absolute zero"

SI prefixes

•Occasionally, a measured quantity may be too large or too small to conveniently use a base unit. •In these cases, we can use an SI prefix in conjunction with any unit to designate a unit which is either larger or smaller than a base unit by some multiple of 10.

Length

•The SI base unit is the meter (m). •In 1983,the meter was redefined as the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second. •One meter is slightly longer than one yard. 1 m = 1.094 yd

angstrom (Å)

•a non-SI unit of length which is, nevertheless, in common use. 1 Å = 10 − 10 m

Units

•a particular physical quantity, defined and adopted by convention, with which other particular quantities of the same kind are compared to express their value. -Units are fixed standards of measurement for different properties, and aremeaningful only when they are defined in terms that do not change and are understood