Chapter 1Chemical Foundations

AP Chemistry

Objectives

• Recall units of measure

• Describe uncertainty in measurement

• Use scientific notation for numbers

• Apply significant figure rules

Units of Measure

• SI Base Units

– Mass

• Kilogram – kg

• 1 kilogram is about 2.20 pounds

– Length

• Meter – m

• 1 meter is about 3 feet

Units of Measure

• Time– Second – s– The time needed for a cesium-133 atom to

perform 9,192,631,770 complete oscillations. • Temperature

– Kelvin – K– 273 K = 0 degrees C

• Amount – Mole – mol– 1 mol = 6.022x1023 particles

Units of Measure

• Current

– Ampre – A

• Luminous Capacity

– Candela – cd

• First five are the most commonly used in chemistry

Volume

• Volume is not an SI Base Unit– Metric system– Powers of 10

• 1 Liter is 1/1000 of a cubic meter

• 1 Liter (L) = 1000 cm3 = 1000 mL

Cubic Meter

Liter

Milliliter

Volume?

• Uncertainty is in the last digit.

Accuracy and Precision

• Accuracy– The nearness of a measurement to its

accepted value

• Precision– The agreement between numerical values – You can be precise without being accurate

Accurate & Precise

NeitherPrecise

• Loss of accuracy due to systematic errors– Error in same direction every time

• Random Error give erratic results– Poor technique

Significant Figures

• All known digits plus one estimated digit in a measurement

What is the length?

• 2 Sig. Fig• 1 Known Digit• 1 Estimated Digit

Significant Figures

• Rule #1

– All Nonzero digits are significant

– Ex. 76.44 mL

– Ex. 285.85 s

Significant Figures

• Rule #2

• “Captive Zeros”

• Zeros appearing between nonzero digits are significant

• Ex. 308.2001 g =

Significant Figures

• Rule #3

• “Leading Zeros”

• Zeros appearing in front of nonzero digits are not significant

• Ex. 0.007036 g

• Takes care of unit changes

Significant Figures

• Rule #4• “Ending Zeros”• Ending zeros are significant if there is a

decimal place• Ex. 53.00 m• Ex. 40000. m• Ex. 40000 m• 40000. is much more precise than 40000

What is the length?

Significant Figures

• Rule #5

• “Exact Numbers”

• Exact number have an unlimited number of significant figures

• Exact numbers are counting numbers or definitions

• 2 cars or 1000g/1kg

Significant Figures

• Rule #6

• “Scientific Notation”

• All numbers that come before the x10n are significant– Must be in proper form

• Ex. 3.33x105

• Ex. 2.04x10-4

Rounding

• 5 and larger round up

• 4 and smaller round down

• Round the following

• 34.567 to 2 SF =

• 756.44 to 4 SF =

• 0.004325 to 3 SF =

• 3436543 to 2 SF =

Addition and Subtraction w/ SF

• Addition and Subtraction

– The answer must have the same number of digits to the right of the decimal as there are in the measurement having the fewest digits to the right of the decimal point

– Ex. 12.11 m + 15 m =

– Number of SF’s does not matter!

Multiplication and Division w/ SF

• Multiplication and Division

– The answer can have no more SF’s than are in the measurement with the fewest total SF’s

– Ex. 55 m / 11.34 s =

Scientific Notation

• A method of representing very large or very small numbers

• M x 10n

– M is a number 1 or larger and less than 10

– n is an integer (positive or negative)

– All digits in M are significant (If in proper form)

Converting to Sci. Notation

• Move decimal so that M is between 1 and 10

• Determine n by counting the number of places the decimal point was moved

– Moved to the left, n is positive

– Moved to the right, n is negative

Examples

• 340,000,000 =

• 5.04x105 =

• 0.00000300 =

• 2.212x10-4 =

Sci. Notation on Calculators

• Enter digits in you calculator using the EE key.

• For TI 83’s it is the 2nd of the comma• For TI 30’s it is a key• Saves key strokes• Fewer OOR mistakes• 3.4x106 = 3.4E6 • 7.4x10-5 = 7.4E-5

Sci. Notatation Math Operations

• Multiply and Divide – Multiply or divide first number– Add exponents (Multiply)– Subtract exponents (Divide)

• Addition and Subtraction– Exponents must be the same– Then add or subtract first number– Exponents stay the same

Calculations

• 3.0x105 + 4.0x105 =

• 4.0x103 – 2.0x102 =

• 7.0x105 * 2.0x104 =

• 8.0x106 / 4.0x10-3 =

• _____4.5x104____ =

6.2x106 * 3.1x10-8

Objectives

• Recall metric prefixes

• Convert numbers from one unit to another

• Describe different temperature scales

• Explain density and perform calculations

• Classify matter into groups

The Metric System

• A system based on powers of ten

• Uses SI Units

• Allows easy work with both large and small numbers

• Prefixes tell us which power of 10 we are using

SI Prefixes (10x larger)Page 9 in your book

• Tera• Giga• Mega• Kilo• Hecto• Deca• Base

1012

109

106

103

102

101

100

1000000000000

1000000000

1000000

1000

100

10

1

T

G

M

k

h

da

SI Prefixes (10x smaller)

• Base• Deci• Centi• Milli• Micro• Nano• Pico•

100

10-1

10-2

10-3

10-6

10-9

10-12

1

.1

.01

.001

.000001

.000000001

.000000000001

d

c

m

μ

n

p

Conversions

• To convert between units set up conversion factors

– Ratios of equality

m

mm

1

1000

km

mx

1

101 3

Convert 67 kg to g

Convert 450 cL to dL

Convert 3.4x108 ng to kg

Converting From Metric To English

• Find ratios that are true

– Page 18 has some equivalents

in

cm

1

54.2

m

in

1

4.39

Convert 763 cm to yd

Convert 1.2 mi/hr to ft/s

Convert 3.8 m2/hr to cm2/s

Temperature

• Many different temp. scales

• All 0 marks based on different ideas

• 0 ºF Coldest saltwater stays a liquid

• 0 ºC Normal Freezing Point of water

• 0 K Molecular motion stops1 K = 1 ºC = 1.8 ºF

Temperature Conversion

• Temp K = 273 + Temp C• Temp C = Temp K – 273

• 0 ºC = 273 K

• If you need any others look up the equ.• TC= (TF – 32)(5/9)• TF = TC(9/5) + 32

Density

• Ratio of mass to volume

• Density = __Mass__

Volume

• Periodic Trend

• Units – Solids – g/cm3

– Liquids – g/mL– Gases – g/L

Density Determination• Mass is determined on a balance

• Volume is measured in two ways– Regular objects can be measured– All objects can use water displacement

Density

• Physical Property– Can be used to identify a substance

Lead 11.35 Iron 7.87

Magnesium 1.74 Zinc 7.13

Copper 8.96

Example: A metal cube has sides measuring 3.00 cm. It has a mass of 242.13g. What is the density?

What is the metal?

Density

• Physical Property– Can be used to identify a substance

Lead 11.35 Iron 7.87

Magnesium 1.74 Zinc 7.13

Copper 8.96

Homework

• p.33 #'s 33a-f,36a-d,42 47,57,68