CHEMISTRY AND NUMBERS

What is Chemistry? the study of the composition of matter

and the changes it undergoes comes from the word alchemy

refers to both an early form of the investigation of nature and an early philosophical and spiritual discipline, both combining elements of chemistry, metallurgy, physics, medicine, astrology, semiotics, mysticism, spiritualism, and art all as parts of one greater force○ example- making lead into gold (tomorrow’s lab- sort

of) five main areas of chemistry one can

study--

1. Organic Chemistry Organic is the study of matter

that contains carbon Organic chemists study the

structure, function, synthesis, and identity of carbon compounds

Useful in petroleum industry, pharmaceuticals, polymers

2. Inorganic Chemistry Inorganic is the

study of matter that does NOT contain carbon

Inorganic chemists study the structure, function, synthesis, and identity of non-carbon compounds

Polymers, Metallurgy

3. Biochemistry Biochemistry is

the study of chemistry in living things

Cross between biology and chemistry

Pharmaceuticals and genetics

4. Physical Chemistry Physical

chemistry is the physics of chemistry… the forces of matter

Much of p-chem is computational

Develop theoretical ideas for new compounds

HONK if you passed p-chem

5. Analytical Chemistry Analytical chemistry

is the study of high precision measurement

Find composition and identity of chemicals

Forensics, quality control, medical tests

Scientific notation consists of two parts:

A number between 1 and 10

A power of 10

n x 10x

Examples Given: 289,800,000 Use: 2.898 (moved 8 places) Answer: 2.898 x 108

Given: 0.000567 Use: 5.67 (moved 4 places) Answer: 5.67 x 10-4

Example

Given: 5.093 x 106

Answer: 5,093,000 (moved 6 places to the right)

Given: 1.976 x 10-4

Answer: 0.0001976 (moved 4 places to the left)

Dimensional Analysis figure what you have and where you are going “cancel out” what you don’t want Use conversion factors (fraction that equals one) example: 23,532 seconds = ? hours

23,532 sec. X 1 min. X 1 hour = 1 60 sec. 60 min.

example: 7463 mm = ? meters 7463 mm X 1 m =

1 1000 mm is your answer reasonable?

6.5 hours

7.463 m

How many minutes are in 2.5 hours?

Conversion factor

2.5 hr x 60 min = 150 min 1 hr

cancel

By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!

Sample Problem

You have $7.25 in your pocket in quarters. How many quarters do you have?

7.25 dollars 4 quarters 1 dollar

X = 29 quarters

A rattlesnake is 2.44 m long. How long is the snake in cm?b) 244 cm

2.44 m x 100 cm = 244 cm1 m

Wait a minute!

What is wrong with the following setup?

1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min

1.4 day x 24 hr x 60 min x 60 sec 1 day 1 hr 1 min

Chemistry In ActionOn 9/23/99, $125,000,000 Mars Climate Orbiter entered Mars’ atmosphere 100 km lower than planned and was destroyed by heat.

1 lb = 1 N

1 lb = 4.45 N

“This is going to be the cautionary tale that will be embedded into introduction to the metric system in elementary school, high school, and college science courses till the end of time.”

Precision vs. Accuracy Precision

the exactness of a measurementyou get almost the same number

every time, even if it is wrong Accuracy

how close the measurement is to the correct answer

precise accurate

Percentage Error[error]

accepted value% error =

What is the percent error if the boiling point of water is measured at 99.2° Celsius?

% error = 99.2°C- 100.0°C X 100% 100.0°C

= 0.8°C X 100% 100°C

= 0.008 X 100% = 0.8%

X 100%

Significant Figures the numbers that are known, plus one more

number that is estimatedSignificant values:

1. Every nonzero digit- 24.7, 0.743, 7142. Zeros between nonzero digits- 7003, 40.79, 1.5033. Zeros at the end of a number and to the right of a

decimal point= 43.00, 1.010, 9.000 Not Significant values

1. Leftmost zeroes acting as place holders- 0.0071, .00090

2. Rightmost zeros acting as place holders- 300, 7000, 27,210

sig fig video

Number (m) Significant figures

47.7 3

0.43 2

1.304 4

0.00023 2

8.00 3

300 1

3.00X102 3

Significant Figures When Calculating:• Addition and Subtraction

– an answer should not be more accurate than your measurements!

– the answer should be rounded to the same number of decimal places as the measurement with the least number of decimal places• 22.75 cm + 98.457 cm + 10. 1 cm• = 131.307 on your calculator• however, 10.1 cm has the least number of

decimal places– therefore, the answer is 131.3 cm

Multiplication and Divisionan answer should not be more accurate than your

measurements!the answer should be rounded to the same

number of significant figures as the measurement with the least number of significant figures○ 0.7 m + 98.457 m○ = 68.9199 m2 on your calculator○ however, 0.7 m has the least number of

significant figurestherefore, the answer is 60 m2

International System of Units (SI)adopted in 1960seven base units which all others can be derived

m, kg, K, s, mol, cd, A

Common Metric Prefixes