# Chapter 1 Chemical Foundations

## Presentation on theme: "Chapter 1 Chemical Foundations"— Presentation transcript:

Chapter 1 Chemical 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
The nearness of a measurement to its accepted value Precision The agreement between numerical values You can be precise without being accurate

Loss of accuracy due to systematic errors
Accurate & Precise Precise Neither 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 mL Ex s

Significant Figures Rule #2 “Captive Zeros”
Zeros appearing between nonzero digits are significant Ex g =

Significant Figures Rule #3 “Leading Zeros”
Zeros appearing in front of nonzero digits are not significant Ex g Takes care of unit changes

Significant Figures Rule #4 “Ending Zeros”
Ending zeros are significant if there is a decimal place Ex m Ex m Ex m 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 to 2 SF = to 4 SF = to 3 SF = to 2 SF =

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 m + 15 m = Number of SF’s does not matter!

Multiplication and Division w/ SF
The answer can have no more SF’s than are in the measurement with the fewest total SF’s Ex. 55 m / 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 = = 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 =

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 T G M k h da 1012 109 106 103 102 101 100 1000 100 10 1

SI Prefixes (10x smaller)
.1 .01 .001 100 10-1 10-2 10-3 10-6 10-9 10-12 Base Deci Centi Milli Micro Nano Pico d c m μ n p

Conversions To convert between units set up conversion factors
Ratios of equality

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

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 stops 1 K = 1 ºC = 1.8 ºF

Temperature Conversion
Temp K = 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 Iron 7.87 Magnesium Zinc 7.13 Copper 8.96

Example: A metal cube has sides measuring 3. 00 cm
Example: A metal cube has sides measuring 3.00 cm. It has a mass of g. What is the density? What is the metal?

Density Physical Property Can be used to identify a substance
Lead Iron 7.87 Magnesium Zinc 7.13 Copper 8.96

Homework p.33 #'s 33a-f,36a-d,42 47,57,68