Chem 120 Chapter 1 Measurements

1.3 Law of conservation of Mass

total mass remains constant during a chemical reaction

paper + oxygen ------>

iron + oxygen ---->

1.4 Matter

Physical States

Solid ________________Liquid ____________________Gas

rigid

incompressible

Chemical Make-up of Universe

1. elements:

O

Ag - (argentum)

Fe - (ferric)

C -

Na - (natrium)

K - (kalium)

W -(wolfram)

Ca -
Co -
Cs -
Cu - (cupric)

On Periodic table

rows (periods)

columns (families)

chemical similar elements in columns

metal on left, nonmetal on right

in box: atomic number - # protons

element symbol

ave. atomic mass

main group elements

transition elements

rare earth elements

2. compounds

elements chemically bond together to form compound

3. elements and compounds _________ change their identity by physical processes

4. chemical processes ________ change the identity of elements into compounds, compounds into elements, and compounds into different compounds

1.5 Measurement

number and unit

A. consider 5 measurements of a stick

4.76 ft, 4.74 ft, 4.76 ft, 4.75 ft, 4.74 ft

AVE. _________________

certain of 4 and 7, some uncertainty in 5 ?

significant figures are the digits in a measurement that are certain plus one that has some uncertainty

thus our number has ________ significant figures (sig figs)

B. Expressing significant figures in measurements

1. all digits are significant and zeros between digits are significant

2. zeros at the beginning of a number are not significant

3. terminal zeros on right of number are significant if following a decimal point

4. terminal zeros on right of number are not clarified without decimal point, thus are assumed insignificant.

7000 ft

Usually write in scientific notation to indicate sig figs

thus 3 sig figs =

Write the following in scientific notation:

40.00

3031

0.0023

0.0440500

2.00

C. Significant Figures in calculations

1. Multiplying and Dividing

give answer as many sig figs

as there are in the measurement

with the smallest number of sig figs

2. Adding and Subtracting

give answer with the same number of decimal places

that are in the measurement

with the smallest number of decimal places

17.421 g + 1.92 g = 19.341g proper sig figs =

1420 mL - 0.122 mL = 1419.878 proper sig figs =

3. Infinite sig figs

All whole numbers used to count items (1, 2, 3, etc)

and all conversion factors ( 1 in = 2.54 cm)

have infinite sig figs

4. Rounding

used to drop non-significant figures by adjusting the last sig fig

look at the leftmost non-significant figures

if 5 or greater, round up one unit

if 4 or less, drop it

7.426

6.93284

1.6 Units used by chemist

_______________ system

Use prefixes to vary base units by multiples of 10 or 1/10

Length

base unit = meter (m) ~ 3 feet (39.37 inches)

Prefix----------------------Length unit----------------Equivalent to:

kilo

deci

centi

milli

micro

Volume

base unit = _________________

PREFIX

kilo

deci

centi

milli

micro

Mass

basic unit = ________

PREFIX

kilo

deci

centi

milli

micro

Common used medical volume = "cc"

means cubic centimeter

1 cc = 1 mL for any liquid

MASS

quantity of matter in an object

mass never changes

WEIGHT

is the force a mass experiences under the pull of gravity.

weight changes as gravity changes

Knoxville Moon

Mass

Weight

TEMPERATURE

^OF (Fahrenheit) water freezes at______^OF, boils at ______^OF

^OC (Celsius or centigrade) water freezes at ___^OC, boils at ______^OC

Room temperature is about 72^OF. What is it in ^OC ?

A patient's temp. is 39.0 ^OC. Does this patient have a fever?

Kelvin scale (absolute zero scale)

K =______________________

What is the boiling point of water on the Kelvin scale?

1.8 Unit Conversions: The FACTOR-LABEL method

1. Always use a number with its units

2. Set up conversion factors

Write equal statements-----------------Write as fractions

1L = 1000 mL

3. Set up conversion factors such that units cancel to get to desired units.

Then cancel units.

Do Math.

EXAMPLES

A. Convert 755 mg to grams.

B. Convert 7.00 L to mL.

C. Convert _____cm to inches. Given that 1.00 in = 2.54 cm.

D. Convert 0.491 miles to cm.

Given that 1.00 mile = 5280 ft and 1.00 in = 2.54 cm.

E. A football field is 100.0 yards long. What is the length of the football field in meters? (Given 1.00 inch = 2.54 cm)

Does answer seem logical?

1.7 Derived Units

_____________ is mass per unit volume

d =

Example I:

A cube measures 3.0 cm on each side

volume =

The cube weighs 88.41 g. What is the density?

d =

Example II:

What is the mass of 55.6 mL of a liquid with

density of 0.810 g/mL?