Language of substances

• Classification of matter• Properties of matter• Element groupings

Classification of matter: degree of uniformity

Heterogeneous matter: sample is not uniform throughout

Homogeneous matter: sample is uniform throughout

Note that the degree of uniformity is completely dependentupon the scale upon which the sample is viewed.

We will expand this classification scheme of matter significantly in the days ahead.

Element: matter that cannot be chemically or physically broken down into simplersubstances

Elements display certain properties. But before we can explore them, we mustestablish a language of properties.

Chemists abbreviate elements with one, two, or three letter symbols, most of which are relatively obvious. Some, however, only make sense in other languages.

Intensive properties: do not depend upon size of sample

Extensive properties: do depend upon size of sample

•Physical Properties can be determined

without changing the chemical makeup of the

sample.

•Some typical physical properties are:–Melting Point, Boiling Point, Density, Mass, Touch,

Taste, Temperature, Size, Color, Hardness,

Conductivity.

•Some typical physical changes are:–Melting, Freezing, Boiling, Condensation,

Evaporation, Dissolving, Stretching, Bending,

Breaking.

•Chemical Properties are those that do change the chemical makeup of the sample.

•Some typical chemical properties are:

–Burning, Cooking, Rusting, Color change, Souring of

milk, Ripening of fruit, Browning of apples, Taking a

photograph, Digesting food.

• Note: Chemical properties are actually chemical changes.

Periodic Table: a visual organization of all the elements that highlights similaritiesin properties or organized progression in properties

• Periods: The seven horizontal rows of the periodic

table.

• Groups: The 18 vertical columns of the periodic

table.

The periodic table is a vast storehouse of information. You would be wise to make ityour friend. There are very few topics we will cover that will not become easier withCompetent use of the periodic table.

• Main Groups:– s-block elements: Two

groups on the left (1 & 2)

– p-block elements: Six groups

on the right (13–18)

• Transition Metal

Groups:– d-block elements: Ten

groups in the middle (3–12)

– f-block elements: Fourteen

groups between 3 & 4 are

called inner transition metals.

Metals: Found on left side of periodic table.

Nonmetals: Found on the right side of periodic table.

Semimetals: Form a zigzag line at the boundary between metals and nonmetals.

SI Units: prefix + unit

Prefix Symbol Factor

exa E 1015

tera T 1012

giga G 109

mega M 106

kilo k 103

deci d 10-1

centi c 10-2

milli m 10-3

micro 10-6

nano n 10-9

pico p 10-12

femto f 10-15

atto a 10-18

Physical Quantity

Name Abbreviation

Mass gram g

length meter m

Temperature Kelvin K

Amount (count) mole mol

Time second s

Electrical current

Ampere A

Energy Joule J

Pressure bar bar

Scientific Notation

350000000105.3

00066.0106.68

4

Scientific Notation and SI: hand in glove

To eliminate a metric prefix, replace the prefix with its mathematical factor.

Example

From Table 1.4 (p.11):

pico (abbrev. as “p”) = 10-12

so 1pA = 1* 10-12 A

TemperatureFC

C

FF

32

5

9

Celsius to Fahrenheit

FFF

CC

32

9

5

Fahrenheit to Celsius

To convert from Celsius to Kelvins, add 273.15 to the degrees Celsius and change units to Kelvins.

To convert from Fahrenheit to Kelvins, first conver to Celsius and then convert to Kelvins.

Volume

Density Density is a ratio of mass to volume. It can be used to change knowledge of one into knowledge of the other.

Accuracy and Precision

Accuracy refers to the degree to which the measurements match a “correct” value.

Precision refers to the degree of closeness between the measurements.

Comprehension question

Significant Figures

1. Counting sig figs

Significant figures is, at heart, a topic for labs.

In a lab, it is a set of rules for establishing how much “credit” you get for a given measurement.

In the lecture hall, it is a set of rules for limiting the output of calculators.

Watch the zeroes!!!

00.0007805900

leading zeroes interior zeroes

trailing zeroes

Non-zeroes are always sig figs.

Leading zeroes are never sig figs.

Interior zeroes are always sig figs.

Trailing zeroes are always sig figs if they are to the right of the decimal point. Trailing zeroes are perhaps sig figs if they are to the left of the decimal point.In scientific notation, all of the number

part (not the exponent part) are sig figs.

Significant Figures

2. Math with sig figs

Multiplication and Division:Answer has same # sig figs as number with FEWEST sig figs

Addition and subtraction:Answer has same # digits to the right of the decimal as number with FEWEST # digits there (# sig figs can change!!!)

Exponents and logs:Don’t ask, don’t tell.

Factor-Label Method

Creating conversion factors:

Using conversion factors:

Comprehension question

Practice your skills

• 1 nautical mile is the distance something travels in one hour if they are travelling at 1 knot.

• A knot (in practice) is 47 feet and 3 inches in 28 seconds.

• How many feet are in one nautical mile?

• How many meters? (1” = 2.54 cm)

Solution

.sec

.25.20

.sec28

.567

.sec28

.3.1.12

.47

1inin

inftin

ft

knot

.1

.6075

.1

.min60

.min1

.sec60

.12

.1

.sec1

.25.201

hr

ft

hrin

ftinknot

First, convert knot into a rate with familiar units

Then convert that rate into a distance per hour.

Given that 1 nautical mile is the distance travelled at 1 knot in one hour,One nautical mile is 6075 feet (or 1852 meters).

Factor-Label Method #1: Conversion Factors

• Problem-solving technique that focuses on doing math that makes the units correct

• The most key skill in this technique is the ability to create and use conversion factors

• Conversion factors are (1) created from equalities and (2) found in all derived units (material properties)

mL

g

1

513.3

Non-SI Unit Equivalencies1 inch = 2.54 cm

1 pound = 0.4535924 kg1 ounce (mass) = 28.3495 kg

1 cal = 4.184 J1 BTU = 1055.06 J1 hp = 745.700 W

1760 yd = 1 mi1 L = 1.057 qt

16 oz (mass) = 1 lb

J

BTU

06.1055

1or

BTU

J

1

06.1055

From your exams:

Conversion Factors

Diamond has a density of 3.513 g/mL or

g

mL

513.3

1

Conversion factors are fractions in which the numerator and denominator have different units

Factor-Label Method #2: unit cancellation

Just like you would:

9

7

4

7

9

4

you can also:J

BTU

JBTU 346000

1

06.1055328

The units are a mathematical entity just like a number and can be multiplied, divided, and cancelled just like numbers too.

So, to convert from unit “X” to unit “Y” you need to create a conversion factor that allows you to cancel the “X” you already have and add a “Y” unit you don’t have.

A A C A C A B C B C B B

Sometimes you cannot get a conversion in a single step—multiple-step conversion work like this:

You want Works as well Because

x =

Comprehension questions