chemistry 1a mr. kimball [email protected]
TRANSCRIPT
Welcome to Chemistry 2A
• Podcasts
• A little about myself
• A little about you– New? Major? ESL? International?– Learning Disorders
• Sign roll sheet
• Get phone numbers of others in class
The Class Syllabus
http://www2.bakersfieldcollege.edu/dkimball
Some students prefer to skim through a course.
If you really want to succeed you need to go deep!
1. Take Responsibility (it’s your education)2. Have Confidence (you can do it!)3. Don‘t Procrastinate (study for final now)4. Read/Listen Precisely (ignore things that just aren’t there)5. Practice (use practice tests)6. Persistence (get up one more time than you fall down)7. Recognize Patterns (most things are done the same way)8. Use Pictures (outline problem)9. Think Sequentially (one step at a time)10. Do Neat work (so you can check it)11. Group Study (explain things to each other)12. Try Something New (don’t keep repeating failures)13. Get Help
Learning Skills
Learning Skills Power Point
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Using This Book
• Concept check problems are found within the chapter with the solutions right there with the problem.
• Exercise problems are found within the chapter with select answers in the back of the book.
• Homework is assigned from the Internet. You should check the Eduspace link from my Main Web site under Chemistry 1a for instructions.
Using This Book
• A CD comes with the book that has tutorials, practice quizzes and other aids. Those not doing well in the class should consider using some of these aids.
• There is also a web site. It has practice tests, flash cards, animations, etc.
(http://college.hmco.com/chemistry/general/ebbing/general_chem/8e/students/index.html )
Chemistry and
Measurement1.1 Modern Chemistry
1.2 Experiment and Explanation
1.3 Law of Conservation of Mass
1.4 Matter
AristotleEarth Air Fire Water
Democritus (460-370 BC)
Greek Philosopher who first coined the word “atomos”.
What Is Chemistry?
• Chemistry is the study of the composition, structure, and properties of matter and energy and changes that matter undergoes.– Matter is anything that occupies space and has
mass.– Energy is the “ability to do work.”
Archimedes
Archimedes lived in Syracuse on the island of Sicily.
Archimedes
A comparison of Archimedes’ Pulleys and Study!
Big Study!
Little Study!
Galileo GalileiFather of the Scientific Method
Heavy things fall faster than light things????
Aristotle
Experiment and Explanation
• Experiment and explanation are the heart of chemical research.– An experiment is an observation of natural
phenomena carried out in a controlled manner so that the results can be duplicated and rational conclusions obtained.
– After a series of experiments, a researcher may See some relationship or regularity in the results.
Experiment and Explanation
• If the regularity or relationship is fundamental and we can state it simply, we call it a law.– A law is a concise statement or mathematical
equation about a fundamental relationship or regularity of nature.
– An example is the law of conservation of mass, which says that mass, or quantity of matter, remains constant during any chemical change.
Experiment and Explanation
• Explanations help us organize knowledge and predict future events.– A hypothesis is a tentative explanation of some
regularity of nature.– If a hypothesis successfully passes many tests,
it becomes known as a theory.– A theory is a tested explanation of basic natural
phenomena.
Experiment and Explanation
• The general process of advancing scientific knowledge through observation, laws, hypotheses, or theories is called the scientific method.
The Scientific Method
Your Assignment:
1. Formulate a Problem.2. Observe and collect Data.3. Interpret Data.4. Test your Interpretation.
Examples:1. Pons and Fleishman, Univ. of Utah.2. Horoscope3. Weather.
Matter: Physical State andChemical Constitution
• There are two principal ways of classifying matter:– By its physical state as a solid, liquid, or gas.– By its chemical constitution as an element,
compound, or mixture.
Solids, Liquids, and Gases• Solid: the form of matter characterized by
rigidity; a solid is relatively incompressible and has a fixed shape and volume.
• Liquid: the form of matter that is a relatively incompressible fluid; liquid has a fixed volume but no fixed shape.
• Gas: the form of matter that is an easily compressible fluid; a given quantity of gas will fit into a container of almost any size in shape.
Elements, Compounds, and Mixtures
• To understand how matter is classified by its chemical constitution we must first look at physical and chemical changes.– A physical change is a change in the form of
matter but not in its chemical identity. – Physical changes are usually reversible.– No new compounds are formed during a physical
change. – Melting ice is an example of a physical change.
Elements, Compounds, and Mixtures (cont’d)
• A chemical change, or chemical reaction, is a change in which one or more kinds of matter are transformed into a new kind of matter or several new kinds of matter.– Chemical changes are usually irreversible.
– New compounds are formed during a chemical change.
– The rusting of iron is an example of a chemical change.
• A physical property is a characteristic that can be observed for material without changing its chemical identity.
• Examples are physical state (solid, liquid,or gas), melting point, and color.
• A chemical property is a characteristic of a material involving its chemical change. – A chemical property of iron is its ability to
react with oxygen to produce rust.
Elements, Compounds, and Mixtures (cont’d)
Matter
Pure Substances
Mixtures
Compounds
(molecules)
Homogeneous
(solutions)
Heterogeneous(most things)
Elements
(atoms)
HydrogenOxygenCopperZinc
GraniteSandWoodOrange Juice
AirSodasOcean WaterAlcoholic drinks
WaterAlcoholSugarSalt
Separate by Physical Processes-filtering-distillation-centrifuging
Separate by Chemical Processes-burning-fermentation-rusting
Separation by distillation.
Elements: sulfur, arsenic, iodine, magnesium, bismuth, mercury. Photo courtesy of American Color.
A mixture of potassium dichromate and iron fillings. Photo courtesy of James Scherer.
Return to slide 15.
A magnet separates the iron filling from the mixture. Photo courtesy of James Scherer.
Return to slide 15.
1.5 Measurement and Significant Figures
1.6 SI Units
1.7 Derived Units
1.8 Units and Dimensional Analysis
Chemistry and Measurement
Measurement and Significant Figures
• Measurement is the comparison of a physical quantity to be measured with a unit of measurement -- that is, with a fixed standard of measurement.– The term precision refers to the closeness of the
set of values obtained from identical measurements of a quantity.
– Accuracy is a related term; it refers to the closeness of a single measurements to its true value.
Precision vs. Accuracy
Measurement and Significant Figures (cont’d)
• To indicate the precision of a measured number (or result of calculations on measured numbers), we often use the concept of significant figures.– Significant figures are those digits in a
measured number (or result of the calculation with a measured number) that include all certain digits plus a final one having some uncertainty.
Scientific Notation
• Useful with very large and very small numbers. • Decimal always after first digit.• Use x 10n where n is the number of decimal places
you must move the decimal to get it just after the first digit.
• Positive exponents represent large numbers. 2,340,000,000,000,000 = 2.34 x 1015 • Negative exponents represent small numbers. 0.00000000000000234 = 2.34 x 10-15
Measurement Accuracy
How long is this steel rod?
There is no such thing as a totally accurate measurement!
Significant Figures
• Numbers that measure or contribute to our accuracy.
• The more significant figures we have the more accurate our measurement.
• Significant figures are determined by our measurement device or technique.
Rules of Determining the Number of Significant Figures
1. All non-zero digits are significant.
203 = 3 sig figs 1.003 = 4 sig figs 1,030.2 = 5 sig figs
2. All zeros between non-zero digits are significant.
234 = 3 sig figs 1.333 = 4 sig figs 1,234.2 = 5 sig figs
Rules of Determining the Number of Significant Figures
3. All zeros to the right of the decimal and to the right of the last non-zero digit are significant.
0.0200 = 3 sig figs 0.1220 = 4 sig figs 0.000000012210 = 5 sig figs
4. All zeros to the left of the first non-zero digit are NOT significant.
2.30 = 3 sig figs 1.000 = 4 sig figs 3.4500 = 5 sig figs
Rules of Determining the Number of Significant Figures
5. Zeros to the right of the first non-zero digit and to the left of the decimal may or may not be significant. They must be written in scientific notation.
2300 = 2.3 x 103 or 2.30 x 103 or 2.300 x 103
2 sig figs 3 sig figs 4 sig figs
Rules of Determining the Number of Significant Figures
6. Some numbers have infinite significant figures or are exact numbers.
233 people 14 cats (unless in biology lab)
7 cars on the highway 36 schools in town
How many significant figures are in each of the following?
1) 23.34
2) 21.003
4 significant figures
4 significant figures3) .0003030
4) 210
5) 200 students
6) 3000
5 significant figures
2 or 3 significant figures
infinite significant figures
1, 2, 3, or 4 significant figures
Using Significant Figures in Calculations
Addition and Subtraction1. Line up the decimals.
2. Add or subtract.
3. Round of to first full column.
23.345 +14.5 + 0.523 = ? 23.345 14.5+ 0.523 38.368 = 38.4 or three significant fingures
Using Significant Figures in Calculations
Multiplication and Division1. Do the multiplication or division.
2. Round answer off to the same number of significant figures as the least number in the data.
(23.345)(14.5)(0.523) = ? 177.0368075
= 177 or three significant figures
Length Mass Volume Time
meter gram Liter second
SI
Sys
tem Km=1000m Kg=1000g KL=1000L 1min=60sec
100cm=1m 1000mg=1 g 1000mL=1L 60min=1hr
1000mm=1m
Bri
tish
12in=1ft 16oz=1 lb 4qt=1gal (same)
3ft=1yd 2000 lb=1 ton 2pts=1qt
5280ft=1mile
Foot pound gallon second
Table 1.5 Relationships of Some U.S. and Metric Units
Length Mass Volume
1 in = 2.54 cm 1 lb = 0.4536 kg 1 qt = 0.9464 L
1 yd = 0.9144 m 1 lb = 16 oz 4 qt = 1 gal
1 mi = 1.609 km 1 oz = 28.35 g
1 mi = 5280 ft 1 lb = 454 g
1 L = 1.06 qt
Table 1.3 SI PrefixesMultiple Prefix Symbol
106 mega M
103 kilo k
10-1 deci D
10-2 centi C
10-3 milli m
10-6 micro 10-9 nano n
10-12 pico p
Units: Dimensional Analysis
• In performing numerical calculations, it is good practice to associate units with each quantity.– The advantage of this approach is that the units
for the answer will come out of the calculation.– And, if you make an error in arranging factors
in the calculation, it will be apparent because the final units will be nonsense.
Unit Conversion
• Sodium hydrogen carbonate (baking soda) reacts with acidic materials such as vinegar to release carbon dioxide gas. Given an experiment calling for 0.348 kg of sodium hydrogen carbonate, express this mass in milligrams.
x 0.348 kg x 103 g
1 kg
103 mg
1 g= 3.48 x 105 mg
Units: Dimensional Analysis
• Dimensional analysis (or the factor-label method) is the method of calculation in which one carries along the units for quantities.– Suppose you simply wish to convert 20 yards to
feet.
– Note that the units have cancelled properly to give the final unit of feet.
feet 60 yard 1feet 3
yards 20
Units: Dimensional Analysis
• The ratio (3 feet/1 yard) is called a conversion factor.– The conversion-factor method may be used to
convert any unit to another, provided a conversion equation exists.
– Relationships between certain U.S. units and metric units are given in Table 1.5.
Unit Conversion
• Suppose you wish to convert 0.547 lb to grams.– From Table 1.5, note that 1 lb = 453.6 g, so the
conversion factor from pounds to grams is 453.6 g/1 lb. Therefore,
g 248 lb 1
g 453.6 lb 547.0
Temperature
• The Celsius scale (formerly the Centigrade scale) is the temperature scale in general scientific use.– However, the SI base unit of temperature is the
kelvin (K), a unit based on the absolute temperature scale.
– The conversion from Celsius to Kelvin is simple since the two scales are simply offset by 273.15o.
15.273C o K
Figure 1.23: Comparison of Temperature Scales
Temperature
• The Fahrenheit scale is at present the common temperature scale in the United States.– The conversion of Fahrenheit to Celsius, and
vice versa, can be accomplished with the following formulas
8.132F
Co
o 32C)( 8.1F oo
Derived Units
• The SI unit for speed is meters per second, or m/s.– This is an example of an SI derived unit, created
by combining SI base units.– Volume is defined as length cubed and has an SI
unit of cubic meters (m3).– Traditionally, chemists have used the liter (L),
which is a unit of volume equal to one cubic decimeter. 33 cm 1 mL 1 and dm 1 L 1
where d is the density, m is the mass, and V is the volume. Generally the unit of mass is the gram. The unit of volume is the mL for liquids; cm3 for solids; and L for gases.
Derived Units
• The density of an object is its mass per unit volume,
Vm
d
A Density Example
• A sample of the mineral galena (lead sulfide) weighs 12.4 g and has a volume of 1.64 cm3. What is the density of galena?
Density = mass
volume=
12.4 g
1.64 cm3= 7.5609 = 7.56 g/cm3