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CHAPTER 1
Chemistry: The Study of Change
CHEMISTRY
The study of matter and the changes it undergoes.
UNITS
Table 1.2 SI Base Units
Base Quantity Name of Unit Symbol
Length meter m
Mass kilogram kg
Time second s
Temperature kelvin K
Amount of substance mole mol
Prefix Symbol Meaning
Tera- T 1012
Giga- G 109
Mega- M 106
Kilo- k 103
Hecto- h 102
Deca- da 101
Deci- d 10-1
Centi- c 10-2
Milli- m 10-3
Micro- 10-6
Nano- n 10-9
Pico- p 10-12
PREFIXES
The number of atoms in 12 g of carbon:
602,200,000,000,000,000,000,000
6.022 x 1023
The mass of a single carbon atom in grams:
0.0000000000000000000000199
1.99 x 10-23
N x 10n
N is a number between 1 and 10
n is a positive or negative integer
SCIENTIFIC NOTATION
568.762
n > 0
568.762 = 5.68762 x 102
move decimal left
0.00000772
n < 0
0.00000772 = 7.72 x 10-6
move decimal right
SCIENTIFIC NOTATION
Making Measurements
SIGNIFICANT FIGURES
Once you start the counting don’t stop!
SIGNIFICANT FIGURES
Rule 1: Every nonzero digit in a measurement is significant.Examples: 24.7 0.22 569Rule 2:Zeros appearing between nonzero digits are significant.Examples: 7003 60.8 0.502Rule 3A ZERO is NOT significant when it is a placeholder. A placeholder is
used to show the location of the decimal point.Examples: .00099 5280 700
SIG FIGS CONT.
Rule 4:Zeros at the end of a number and to the right of a decimal
point are always significant.Examples: 86.0 46.00 1.010Rule 5:When a number is counted or defined within a system of
measurement, there is an infinite amount of significant digits.
Examples: 11 students 100 cm = 1 m
24 mL
3001 g
0.0320 m3
6.4 x 104 molecules
560 kg
COUNT THE SIG FIGS:
The answer cannot have more digits to the right of the decimalpoint than any of the original numbers.
89.3321.1+
90.432 round off to ________
one significant figure after decimal point
3.70-2.91330.7867
two significant figures after decimal point
round off to ________
SIG FIGS – Addition and Subtraction
The number of significant figures in the result is set by the original number that has the smallest number of significant figures
4.51 x 3.6666 = 16.536366 = _______
3 sig figs round to3 sig figs
6.8 ÷ 112.04 = 0.0606926
2 sig figs round to2 sig figs
= _______
SIG FIGS – Multiplication and Division
1. Determine which unit conversion factor(s) are needed
2. Carry units through calculation
3. If all units cancel except for the desired unit(s), then the problem was solved correctly.
1 L = 1000 mL
How many mL are in 1.63 L?
1L
1000 mL1.63 L x = 1630 mL
1L1000 mL
1.63 L x = 0.001630L2
mL
FACTOR LABEL METHOD
The speed of sound in air is about 343 m/s. What is this speed in miles per hour?
1 mi = 1609 m
1 min = 60 s 1 hour = 60 min
343ms
x1 mi
1609 m
60 s
1 minx
60 min
1 hourx = 767
mihour
meters to miles
seconds to hours
Important things to consider when solving problems and performing
experiments….
Volume – SI derived unit for volume is cubic meter (m3)
1 L = 1000 mL = 1000 cm3 = 1 dm3
1 mL = 1 cm3
Matter - anything that occupies space and has mass.
mass – measure of the quantity of matter
SI unit of mass is the kilogram (kg)
weight – force that gravity exerts on an object
weight = c x mass
on earth, c = 1.0
on moon, c ~ 0.1
A 1 kg bar will weigh
1 kg on earth
0.1 kg on moon
Density – SI derived unit for density is kg/m3
1 g/cm3 = 1 g/mL = 1000 kg/m3
density = mass
volume D = mV
A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass?
d = mV
m = d x V = 21.5 g/cm3 x 4.49 cm3 = 96.5 g
For Water: 1g/mL
K = 0C + 273.15
0F = x 0C + 3295
273 K = 0 0C 373 K = 100 0C
32 0F = 0 0C 212 0F = 100 0C
Convert 172.9 0F to degrees Celsius.
0F = x 0C + 3295
0F – 32 = x 0C95
x (0F – 32) = 0C95
0C = x (0F – 32)95
0C = x (172.9 – 32) = 78.395
Graphing
Distance vs. Time
Dep
ende
nt V
aria
ble
Independent Variable
Line of Best Fit
Accuracy – how close a measurement is to the true value
Precision – how close a set of measurements are to each other
Percent Error:
Percents and Percent Error
Measured Value - Accepted Value
Accepted ValueX 100
Example: The mass of a compound measured in a lab was 25.0 grams. The accepted value for this compound is 24.5 grams. Calculate the percent error.
25.0 g- 24.5 g24.5 g
X 100 = 2.04 %
Scientific Method
SCIENTIFIC METHOD
logical approach to solving problems
ObservationProblemHypothesisExperiment
Data Analysis
Conclusion
You have 15 seconds to count how many letter “F”s you see in
the following statement.
FEATURE FILMS ARE THE RESULT OF YEARS OF
SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCES OF
YEARS.
Observations
Qualitative: quality, non-numeric terms
Quantitative: quantity, numerical description
How observant are you?!?
MATTER: ANYTHING THAT OCCUPIES SPACE AND HAS MASS
MATTER
State of Matter
Volume Shape Density Compressibility Motion of Molecules
Gas
Liquid
Solid
Plasma
Three States of Matter
solid liquid gas
Phase Changes
phase diagram: summarizes the conditions at which a substance exists as a solid, liquid, or gas.
Phase Diagram of Water
Phase Diagram Points
critical point: above this point a substance becomes a supercritical fluid critical temperature (Tc): temperature above which the gas
cannot be made to liquefy, no matter how great the applied pressure.
critical pressure (Pc): minimum pressure that must be applied to bring about liquefaction at the critical temperature.
triple point: point at which all three phases coexist
1. Pure Substance: form of matter that has a definite composition and distinct properties
2. Mixture: combination of two or more substances in which the substances retain their own identities.
water, ammonia, sucrose, gold, oxygen
Classification of Matter
• mixed together physically• can usually be separated
1. Homogenous mixture – composition of the mixture is the same throughout.
2. Heterogeneous mixture – composition is not uniform throughout.
Examples: cement, iron filings in sand
1.4
Examples: soft drink, KoolAid
Types of Mixtures
Mixture Pictures
•solution: mixture that remains uniformly mixed•solute: part of the mixture that gets dissolved•solvent: part of the mixture that does the
dissolving
•suspension: mixture where visible particles settle
•colloid: mixture where particles are unevenly distributed but do not separate, positive Tyndall Effect
Types of Mixtures
Hom/Het? Soln/Susp/Coll?
Fog ____________ ___________
Paint ____________ ___________
Syrup ____________ ___________
Physical means can be used to separate a mixture into its pure components.
magnet
1.4
distillation
Methods of Separation
Strainer
Filtration
Physical
Evaporation
Centrifuge
Distillation
PASTA/WATER SAND/IRON FILINGS
SALT /WATER
BLOOD FOOD COLORING/WATER
SAND/WATER
Element:
•all atoms are the same
•cannot be broken down by physical or chemical means
• 114 elements named on the Periodic Table• 83 elements occur naturally on Earth
gold, aluminum, lead, oxygen, carbon• many elements have been created by scientists
technetium, americium, seaborgium
Compound:
•2 or more elements combined
• Cannot be broken down by physical means
•Can be broken down by chemical means
•Appears different from original elements
•Fixed ratios in definite proportionsWater (H2O) Glucose (C6H12O6)
Ammonia (NH3)
PHYSICAL AND CHEMICAL CHANGES
Physical Properties and Physical Changes
physical property: characteristic that can be observed or measured without changing the identity of the substance.
• melting point, boiling point, density
physical change: change in a substance that does not involve a change in the identity of the substance.
• grinding, cutting, melting, and boiling
Physical Properties
Intensive: INDEPENDENT of amount of matter present (sample size) Example: density, color, melting point
Extensive: DEPENDENT on the amount of matter present (sample size) Example: mass, length, volume
Chemical Properties and Chemical Changes
chemical property: a substance’s ability to undergo changes that transform it into different substances
Example: combustibility, reactivity
chemical change: change in which one or more substances are converted into different substances
Example: rusting, cooking food
Evidence of a Chemical Change
1. Color change
2. Temperature change
3. Production of a gas
4. Change in odor
5. Formation of a precipitate Precipitate: insoluble solid that separates out of solution
physical change does not alter the composition or identity of a substance.
chemical change alters the composition or identity of the substance(s) involved.
ice meltingsugar dissolving
in water
hydrogen gas burns in oxygen gas to form water
Physical or Chemical?
Remember: