Chemistry 211
General Chemistry
Ebbing and Gammon
John A. Schreifels
Chemistry 211
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WHY STUDY CHEMISTRY?
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Chemistry is important to us all.
Chemistry major is reasonably likely to
find a job after graduation!
Career advisors suggest a broad
background.
Many students end up doing chemistry
after graduation because of the
overcrowding in their field.
John A. Schreifels
Chemistry 211
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SUCCESSFUL STRATEGIES
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Memorize strategies not equations!
Study a lot!
Self-evaluate after quiz results.
Old examinations on the WEB.
John A. Schreifels
Chemistry 211
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LEARNING TOOLS
• Textbook: read chapter; work lots of problems.
• Other textbooks (check the library as well as
used bookstores.
• Tutoring center – Student Union Building II
Room 2002A
• Classmates
• General Chemistry WEB page:
http://osf1.gmu.edu/~jschreif/genchem/
• Instructor
John A. Schreifels
Chemistry 211
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Chapter 1: Matter and Measurement
Overview:
• The Study of Chemistry
• Classifications of Matter
• Properties of Matter
• Units of Measurement
• Uncertainty in Measurement
• Dimensional Analysis
• Basic Math Concepts (see Appendix A)
John A. Schreifels
Chemistry 211
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The Study of Chemistry
• Chemistry = the study of the composition,
properties and transformations of matter.
• Matter = physical material of the universe.
• Elements = basic building blocks of all other
forms of matter.
• Atoms = small particles derived from one the
elements. All matter can be described in terms
of the interactions of atoms with each other.
• Molecules (compounds) = combination of two or
more atoms. Most common form for atoms.
John A. Schreifels
Chemistry 211
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Classification of Matter
States of Matter
• Solid: Rigid StructureLiquid:Less Rigid Structure
Gas:Loose StructurePlasma:Gaseous atoms or small
molecules in an ionized state.
• Substances and mixtures:
• Substance: matter having a fixed composition and
distinct properties. Can be either an element or a
compound.
– Element: a substance containing only one type of atom. E.g. Na,
H 2.
– Compound: a substance composed of atoms from two or more
elements chemically combined.
• Mixture: matter composed of two or more substances.
Air composed of hydrogen, oxygen, nitrogen, etc.
John A. Schreifels
Chemistry 211
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Classifications of Matter (cont’d)
• Mixtures:can be separated by physical means
into two or more substances.
– Homogeneous: Composition constant in all parts of
sample
– Heterogeneous: Composition not-constant.
• Mixtures separated by:
– Filtration: Mixture consists of a solid and liquid; liquid
separated by filtration.
– Chromatography: Separates mixtures by distributing
components between a mobile and stationary phase.
– Distillation: Liquid mixture is boiled; components in
the mixture boil off at different temperatures.
John A. Schreifels
Chemistry 211
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LAW OF DEFINITE PROPORTIONS
• Law of definite proportions: a pure compound
always contains definite (constant) proportions
by mass of the elements in the compound.
E.g. Data from analysis of cyclopropane was found
to contain 6.00 g of carbon and 1.00 g of
hydrogen. If another sample was analyzed and
found to contain 24.0 g of hydrogen, how many
grams of carbon would it contain?
John A. Schreifels
Chemistry 211
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CONSERVATION OF MASS
• Law of conservation of mass: mass is neither
created or destroyed during a reaction.
• The atoms form new bonds and thus are present
after reaction only bound to some other atoms.
• E.g. 2H2(g) + O2(g)  2H2O(l); 2 g of H2 plus 16
g of O2 produce how many grams of water?
John A. Schreifels
Chemistry 211
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Properties of Matter
• Physical: properties that can be measured without
changing the chemical composition of the substance –
E.g. melting point, smell, density.
• Chemical: properties that described a substance’s
reactivity. E.g. Alkali metals react to form positively
charge substances; halogens form negatively charged
substances
• Intensive: physical or chemical property that does not
depend upon the amount of the substance. Temperature,
density, etc.
• Extensive: physical or chemical property that depends
upon the amount of material. E.g. two tanks of propane
produce twice as much heat when burned as one tank.
John A. Schreifels
Chemistry 211
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Units of Measurement
• Mass, temperature and volume are commonly measured in the lab.
• SI (System International) internationally accepted measurement
system for measuring: Mass, length, temperature, etc.
• Basic Units:
– Mass: measured in grams; tells how much of an object there is;
related to weight, which is the gravitational pull on the object.
– Length: measured in meters
– Temperature: measured in K or °C. Each is based upon the
same reference temperatures: freezing and boiling point of
water.
• Conversion from one scale to the other based upon change in height
of mercury between two temperatures. i.e. h = kiTi
E.g. what is the temperature in the centigrade scale if it is 44°F?
John A. Schreifels
Chemistry 211
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Temperature Conversions
T2 T2,ref
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temperature scales use:
T1
T1,ref
Where Ta,ref = Tb,a – Tf,a and Ta = Ta – Tf,a
E.g. Determine the temperature in the centigrade
scale corresponding to 76°F.
John A. Schreifels
Chemistry 211
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Units of Measurement(cont’d)
• Prefixes make it possible to express
measurements in a more convenient manner.
• Derived Units:
• Speed: distance per elapsed time: m/s
• Volume: m3; volume often expressed in liter (L)
• Density: mass per volume, g/m3
E.g. 100 g of table salt occupies 46.2 g. What is
its density?
E.g.2: The density of liquid bromine is 3.12 g/mL.
What is the mass of 150 mL of bromine?
John A. Schreifels
Chemistry 211
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Dimensional Analysis
Often necessary to convert from one type of unit to another.
• The method of dimensional analysis is used:
– Multiply original number by conversion factors which change
from one unit to another.
– Conversion factor is the relationship between two units.
• Can involve derived units.
• Determine:
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? micrometers in 100 pm;
? ng in 55x105 kg
? kg/m3 in 3.45 g/mL
? pm2 in 6.22x106 cm2
? Mm in 256000 m
John A. Schreifels
Chemistry 211
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SIGNIFICANT FIGURES
• All measurement made at a certain level of uncertainty and are often
made several times to reduce it.
• Precision: closeness of measured values.
• Accuracy: closeness of measured value to the correct answer.
• Significant figures in reported measurement indicate its precision.
Rules:
– Numbers (except zeroes) at beginning of the number sequence are
significant.
– Zeroes at the end of the number and to the right of the decimal point are
significant.
– Zeroes at the end of the number and to the left of the decimal point are
not necessarily significant.
• Avoid ambiguities by expressing in scientific notation: Ax10a where
A is a number between 1 and 9.999 and a is an integer.
• Exact numbers are known to an infinite number of significant figures.
John A. Schreifels
Chemistry 211
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SIG FIG AND CALCULATIONS
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Results of measurements often used to
calculate some number. How many significant
figures (sig fig) should the resulting number
have?
Rules:
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Addition and subtraction of numbers: Add all
numbers; express to same number decimal places
as the original number with the least number of sig.
figs.
Multiplication and division of numbers: Do
calculation and then round to same number of sig
figs as the number with least number of sig fig.
John A. Schreifels
Chemistry 211
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ROUNDING
• Rounding up or down is required to obtain correct number of
significant figures.
• Rules: If the number immediately after the last digit to be saved is:
– >5 round up (add 1 to previous digit).
– <5 round down (drop number).
– = 5 round up if the last digit to be saved is an odd number; round down
if even.
E.g.1 Round each to three significant figures: 0.2226, 0.22225, 5555,
554523
E.g. 2 Express the following in the correct number of significant
figures:
• 10000.0  3.14159
• 142.7 + 0.081
• 6.246 + 8.139  12.75
• 19.69  0.041 + 1.27
John A. Schreifels
Chemistry 211
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Basic Math (see appendix)
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Essential to know HS Algebra II well!
Multiplication of two numbers: add the exponents for the powers of ten and multiply
the two numbers together. Solve:
2.5x1052.0x105 .
1.25x1024
6.22x1023
Powers and roots: For (Ax10n)m raise A to the m power and multiply n by m
Solve: (2.11x105)3
Log and antilog(natural and base ten):remember the definition of a logarithm: log x =
z where x = 10z. The antilog of z in the example would be x .
log xy = log x + log y
x
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log  log x  log y
y
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log xa  a log x
Proportionalities:
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LinearSquared Inverse -
John A. Schreifels
Chemistry 211
y = mx + b
y = mx2 + b
P = kT
R = k[A]2 (second order reaction)
y
P
m
b
x
m
V
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Basic Math Problems
• Eg. The pressure of a gas was 1.00 atm. at 273
K. What was the pressure at 373 K?
• E.g. 2 The rate of a second order reaction was
2.50x102 s1 when the concentration was 0.100
M. What would the rate be when the
concentration is 0.250 M?
• E.g. 3 A gas occupied a volume of 12.5 L when
the pressure was 2.00 atm. What volume would
it occupy if the pressure increased to 3.75 atm?
John A. Schreifels
Chemistry 211
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