Unformatted text preview: CHEMISTRY 1211
PRINCIPLES
PRINCIPLES
OF
CHEMISTRY I
CHEMISTRY
1 CHAPTER 1 CHEMICAL FOUNDATIONS 2 1.1 Chemistry – What is it?
• Chemistry is often described as a central science
• Chemistry is the science that describes matter.
(its properties, the changes it undergoes, and the
energy changes that accompany those processes.)
3 macroscopic symbolic microscopic
(Atoms and molecules)
4 SiO2 5 The Nature of
The
Matter
Matter Matter is the material of the universe. It occupies
6
space and has mass.
space CHEMISTRY:STUDY OF MATTER
MATTER
i ts structure and properties i ts transformation from one form to another
7 Atoms and Elements
• Matter is composed of various types of atoms;
• Atoms: The smallest particle of an element that
maintains its chemical identity through all
chemical and physical changes.
• Element: a substance that cannot be decomposed
into simpler substances by chemical means.
8 Atoms and Elements
• One substance changes to another by
recognizing the way the atoms are
attached to another. 9 1.2 The Scientific Method
Hypothesis Observation
Observation Experiment to test the hypothesis A law summarizes what happens: a theory (model) is an attempt to
law
theory
explain why it happens.
e.g. the law of conservation of mass; Bohr’s quantum model,
Einstein’s relativity.
Einstein’s 10 1.3 UNITS OF MEASUREMENT
UNITS • We make QUALITATIVE
We
QUALITATIVE
observations of reactions — changes in
color and physical state.
color
• We also make QUANTITATIVE
We
MEASUREMENTS, which involve
MEASUREMENTS which
numbers + units.
numbers
11 1.3 UNITS OF MEASUREMENT
UNITS Use SI units — based on the
Use SI
metric system
metric English system
12 Write the units: In 1999, the $125 million Mars
Climate Orbiter spacecraft was lost
when it entered the Martian
atmosphere 100 km lower than
planned. The navigation error
would have been avoided if people
had labeled their units of
measurement.
Engineers who built the spacecraft
calculated thrust in the English
unit, pounds of force. Jet
Propulsion Laboratory engineers
thought they were receiving the
information in the metric unit,
newtons.
13 SI base units used in chemistry
measurement unit symbol Mass Kilogram kg Length Meter m Temperature Kelvin K time Second s or sec Amount of substance Mole mol Electric current Ampere A Luminous intensity Candela cd
14 prefixes
prefixes
• 1 kilometer (km) = 1000 meters (m)
• 100 cm
100 = 1m • 1000 mm = 1m • 106 µm = 1m • 109 nm =1m 15 VOLUME
VOLUME TIME
TIME 1000 mL = 1L
1 mL = 1cc = 1 cm3 60 s = 1min
60 min = 1hr
60 MASS
1 kg = 1000 g
1 mg = 0.001 g
mg
16 Unit factor method
2.54 cm = 1 in
2.54 cm
2.54 Unit factor:
Unit =1 Or 1 in 7.86 cm ×
7.86 1 in
in
2.54 cm
2.54 = 7.86
7.86 1 in
in
2.54 cm
2.54 =1 in = 3.09 in 2.54
2.54 17 Mass and Weight
• Mass: a measure of the resistance of an object
to a change in its state of motion (F = ma).
acceleration
acceleration • Weight: a force exerted on a object by gravity
on the earth (weight = mg).
acceleration due to gravity
acceleration • Mass ≠ weight
18 1.4 Every measurement has uncertainty
Greater number of digits in the measurement, more certainty Figure 1.7 (1.9) 20.15 mL
Certain digits; uncertain digits
measuring device chosen: how much uncertainty we will
accept
19 Uncertainty
? * Equipment, calibration
* person making the measurement
20 Reading a measuring device:
We always estimate the RIGHTMOST digit
Uncertainty can be expressed with the ± sign
Or assume an uncertainty of 1 unit in the rightmost digit 21 •
•
•
• 4.24 cm
4.23 cm
4.28 cm
4.28 cm
uncertain digit: estimated Certain digits
22 Graduated
Graduated
cylinder
cylinder Buret 34 33 Beaker 40 40 30 30
32 20
20 31
33.15 10 +/ 0.01 mL 10
33.1 +/ 0.1 mL 33 +/ 23 1 mL Precision and accuracy: figure 1.8 (1.10)
Precision: reproducibility random errors Accuracy: close to actual value systematic error If systematic errors are absent, we assume the average of a series of precise
measurement is accurate (or close to the true value).
Understand the sample exercise 1.2 on page 12 13. 24 Absolute Uncertainty (Absolute Error) The absolute uncertainty (usually called absolute
error) is the size of the range of values in which the
"true value" of the measurement probably lies.
If a measurement is given as 4.5 cm, the absolute
uncertainty is 0.1  0.5 cm. (always 15 digits) Relative Uncertainty (Relative Error)
Relative uncertainty is the ratio of the absolute uncertainty of a
measurement to the best estimate.
It expresses the relative size of the uncertainty of a
measurement (its precision).
25 1.5 Determining which figures are significant Significant digits: digits that indicate the
digits
precision of measurements; digits of a
precision
measured number that have uncertainty
only in the last digit.
last 26 1.5 Determining which figures are significant
• Rules:
• 1. Non zero integers
Leading zeros 2. Zeros Captive zeros Trailing zeros 3. Exact numbers
4. Mathematical operations 27 Significant figures and calculations
• 0.01008
• Leading zeros • 1008
• Captive zeros • 1008.0
• Trailing zeros with and without a decimal point • 1000 28 EXPONENTIAL NOTATION
& SIGNIFICANT FIGURES
SIGNIFICANT
0.000 000 28 = ? 23.742 has ? significant figures 1 x 10 4 0.00000023 ? 1 x 104 =?
=? 29 Calculations
• Addition & subtraction • Multiplication & division 30 Multiplication & division • Addition and subtraction • Exponential notation:
• 75,000000 =
• 0.00635 = 31 Sig figs in calculations
In a calculation keep track of sig figs
Cannot have more sig figs in answer than in the original data Suppose you want to find the density of a new ceramic:
You measure the mass on a balance: 3.8056 g and its volume is
2.5 mL
Density will be : 1.5222 g/mL or 1.5 g/mL? 32 FACTOR LABEL METHOD
or
DIMENSIONAL ANALYSIS
DIMENSIONAL
A procedure in which the equations
are set up so that all the unwanted units
are
cancel and only the desired units remain
cancel
33 1.7 Calculations Using Temperature
1.7 T (K) = tt((°C) + 273.15
T (K) = °C) + 273.15
•• Body temp. = 37 °°C + 273 = 310 K
Body temp. = 37 C + 273 = 310 K
Body
Body •• ooF = 9/5 ooC + 32
F = 9/5 C + 32
9/5
9/5
•• ooC=5/9 ((oF– 32)
C= 5/9 oF – 32)
34 Temperature Scales
Temperature
Fahrenheit
Boiling Point of water 212
180° Freezing Point of water Absolute zero 32  459o Celsius Kelvin 100 373.15 100° 0  273o 100° 273.15 0
35 1.8 DENSITYa fundamental property
by which a particular
kind of matter can be
characterized and
identified
Density = mass per unit volume
36 D=M/V M=VD V=M/D Volume is typically in mL or cm3
( 1mL = 1 cm 3 )
Mass is typically in grams.
Density is typically in g/mL or g/cm 3
37 EFFECT OF
TEMPERATURE ON
DENSITY
DENSITY
D= M
V Volume increases with temperature
Volume
and if mass remains constant, density must ?
38 Problem: A piece of copper has a mass
Problem of 57.54 g. It is 9.36 cm long, 7.23 cm
wide, and 0.95 mm thick. Calculate
density (g/cm3).
density 39 SOLUTION
SOLUTION
1. Get dimensions in common units.
convert 0.95 mm into cm :
1 cm = 10 mm
Conversion factor : 1 cm/10 mm
0.95 mm x 1cm/10 mm = 0.095 cm
0.95 40 SOLUTION
SOLUTION
2. Calculate volume in cubic centimeters.
9.36 cm x 7.23 cm x 0.095 cm = 6.4 cm3
6.4 3. Calculate the density :
3.
Mass/volume = 57.54g/6.4 cm3 = 8.9906 g/cm3
57.54g/6.4
8.
answer reported as = 9.0 g/cm3
answer
9.0
41 1.9 PROPERTIES OF
MATTER
MATTER CAN EXIST IN 3 STATES :
MATTER
SOLID, LIQUID, GAS
SOLID, PHYSICAL CHEMICAL
42 What are some physical
properties?
properties?
• color
• melting and boiling point
melting
(physical state – solid,
liquid, gas)
liquid,
• Odor • DENSITY
43 Physical Change:
A physical change is a change in the
physical form of a substance, not in its
chemical composition. 44 Some physical changes
physical
would be
would
• boiling of a liquid
• melting of a solid
• dissolving a solid in a
dissolving
liquid to give a
homogeneous mixture
— a SOLUTION.
SOLUTION
45 Chemical Properties
Chemical
Chemical properties of a substance are
those that describe how the substance
interacts with other substances to produce
new substances 46 Chemical Changes
Chemical
A chemical change or chemical reaction
involves the transformation of one or more
atoms or molecules into one or more
different molecules. Aluminum
+
Bromine Aluminum Bromide
47 In each case, decide if each underlined property is a
physical or chemical property:
a) The normal color of sulfur is yellow.
b) Iron is transformed into rust in the presence of
air and water.
c) Dynamite can explode.
d) The density of uranium metal is 19.06 g/mL.
e) Aluminum metal melts at 933 K.
f) Chlorophyll, a plant pigment, is green.
g) Copper can be hammered into thin sheets
48 In each case, decide if the change is a
chemical or physical change.
a) A cup of household bleach changes the
color of your favorite Tshirt from purple to
pink.
b) Water vapor in your breath condenses in
the air on a cold day.
c) Plants use carbon dioxide from the air to
make sugar.
d) Butter melts when placed in the sun.
49 Puzzle time: keep your brain active … If
2 * 3 = 10
7 * 2 = 63
6 * 5 = 66
8 * 4 = 96 ? Then:
9 * 7 = ???? Want to know the answer? I’ll let you know in recitation. 50 ...
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 Spring '10
 LuiKang
 Chemistry, Mass, International System of Units

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