Transcript Chapter 1 Introduction: Matter and Measurement

CHM 1045: General Chemistry and
Qualitative Analysis
Unit 1
Introduction:
Matter and Measurement
Dr. Jorge L. Alonso
Miami-Dade College –
Kendall Campus
Miami, FL
Textbook References:
•Module #1
Matter
And
Measurement
Scientific Method:
A systematic approach to solving problems.
Observation: the detection of a phenomenon by our sensory organs or their
extensions (instruments).
Scientist study CAUSE  EFFECT Relationships
Which factors affect the behavior of gasses?
{GasVariables}
η,P, V, & T
Hypothesis: initial or tentative explanation
of the causes of a phenomenon.
Experiment: carefully designed hypothesis
testing; done by controlling all the
variables except your suspected CAUSE
(independent variable, x) which is Matter
And
manipulated in order to observe itsMeasurement
EFFECT (dependent variable, y).
Experiment: carefully designed hypothesis testing; done by controlling all the variables
except your suspected CAUSE (independent variable, x) which is manipulated in order
to observe its EFFECT (dependent variable, y).
V
1
P
OR
Dependent
Variable
V=
k
P
Also,
P↑V↓=k
Boyle’s Law
Independent Variable
Law: concise verbal or mathematical summary for a variety of observations and
experiences.
Theory: a comprehensive explanation for natural phenomena that has withstood
repeated analysis and experimentation.
Kinetic Molecular Theory
Matter
And
Measurement
What is the universe composed of?
Matter: Anything that has mass and takes up space.
Chemistry
•Chemicals
•Substances
•Things
Energy: the ability to perform an activity (work).
•
•
•
•
Physics
Kinetic (motion & heat)
Electromagnetism (light, electricity & chemical bonds)
Matter
And
Nuclear
Measurement
Gravity
{Matter with Energy}
Chemistry: The study of matter and
the changes it undergoes.
Describing Matter: Physically and Chemically
(1) Physical Properties
(3) Chemical Properties
(2) Physical Change
(4) Chemical Change
(reactions & equations)
Matter
And
Measurement
Let’s get Physical!
Physical Properties: The
H2O (g)
physical characteristics
(appearance) of matter.
H2O (s)
H2O (l)
Physical changes occur without
changes in the composition of
matter.
Physical change:
H2O (s)

H2O (l)
 H2O (g)
Chemical change:
2 H2O (s)

2 H2 (g)
+ O2 (g)
State or phase (s,l,g), color, mass,
volume, density, melting & boiling
points, solubility, etc
Physical Changes:
Changes in the physical
properties of matter.
Changes of: state (s l g),
density, temperature, shape,
Matter
volume, etc.
And
Measurement
Heat Energy & Phase (State) Changes
(fusion)
Matter
And
Measurement
Phase Changes = Changes of State
Kinetic Energy & States of Matter
Heat = Kinetic Energy  Temperature
c. pt.
f. pt.
(condensation point)
(freezing point)

b. pt.
m. pt
(melting point)
(boiling point)
Density (mass per unit volume)
For H2O:
m.pt. = f.pt = 0OC
b.pt. = c.pt = 100OC
For Methanol: m.pt. = f.pt = -98OC b.pt. = c.pt = 65OC
{KineticMolecularTheory: PhaseChange}
Matter
And
Measurement
Heating Curve: Energy & Phase Changes
Heating
water
vapor
Heating
liquid
water
Heating
solid ice
Heat of Vaporization
Heat of Fusion
0OC
For H2O:
m.pt. = f.pt =
For Methanol:
m.pt. = f.pt = -98OC
b.pt. = c.pt =
100OC
b.pt. = c.pt = 65OC
Matter
And
Measurement
Let’s get Chemical!
What happens when you add Chemical Properties:Can only
Na to water? K?
be observed when a substance
reacts and is changed into
another substance.
{Na & K in H2O}
Does it react? With which
substance does it react?
Flammability?
Corrosiveness?, etc.
Is this chemical or physical
change?
Chemical change is always
accompanied by physical change!
Chemical Changes: The
changes that occur in the
process of producing new
substances. Combustion,Matter
And
oxidation, decomposition, etc.
Measurement
Describing Chemical Change
Chemical Reaction: the actual
phenomenon that occurs when
chemicals change in composition.
Chemical Equation: a symbolic
representation of a chemical
reaction. Based on the Atomic
Theory.
Quiz Question:
Write the balanced chemical equations for the
reactions of (1) Sodium (Na) + Water (HOH) Matter
And
(2) Potassium (K) + Water
Measurement
Chemical Reactions and Equations
+ +
2 Na + 2 HOH  2 NaOH + H2
2 K + 2 HOH  2 KOH + H2
(Hint: single displacement or replacement reaction)
Matter
And
Measurement
Matter and the Atomic Theory
•
•
•
•
Atoms are the building blocks of all matter.
Elements are made of the same kind of atom.
Compounds are made of two or more different kinds of atoms.
Matter
And
Mixtures are composed of different elements/compounds
Measurement
together.
Heterogeneous
Classification of Matter
*
Cu(NO3)2
Mixtures
(Heterogeneous)
Physical
Homogeneous
Mixtures
Separation
Solutions
(Homogeneous)
Physical
Cu(NO3)2 (aq)
Separation
Cu(NO3)2 (s)
Compounds
Chemical
Decomposition
Elements
Pure
Substances
Matter
And
Measurement
Separatory Techniques
• methods of physically separating (purifying)
substances from mixtures and solutions into pure
substances.
• based on differences in physical properties of the
substances present in the mixture/solution.
1. Filtration – by solubility vs. insolubility
2. Metal Smelting & Refining - by differences in
melting point (ability to form a liquid)
3. Distillation –by differences in boiling points
(ability to form a gas)
4. Chromatography – by differences in degree of
solubility
Matter
And
Measurement
(1) Filtration: Separates insoluble solid
substances from liquids and solutions.
Mixture:
K2Cr2O7(s)
+NaNO3(s)
+ H2O
K2Cr2O7(s)
NaNO3(aq)
Matter
And
Measurement
(2) Metal Smelting & Refining
These techniques are used to differentially melt mixtures
of metals (alloys) by means of their different melting points
(ability to form a liquid when heated).
The sweat furnace operates at a temp at which one metal
is selectively melted from a component, leaving the metal with the
higher melting point, usually a ferrous metal as a recoverable
solid. Example: mixture of Cu + Zn, heated to 500°C
Matter
And
Measurement
*
(3) Distillation: Separates homogeneous mixture on the
basis of differences in boiling points (ability to form a gas).
Substance
b.pt.
Ethyl Alcohol
77oC
Water
100oC
Sodium Chloride
1413oC
Solution:
Alcohol +
Matter
And
Measurement
Distillation of Hydrocarbons:
Petroleum Refinery Towers
compounds composed of molecules arranged in a long chain of carbon
atoms with hydrogen atoms attached to the carbon chain.
Name (b.pt. C) # C
Structural Formula
Methane (-162)
1
CH4
Ethane (-89)
2
CH3CH3
Propane (-42)
3
CH3CH2CH3
Butane (-0.5)
Pentane (36)
4
5
CH3CH2CH2CH3
CH3CH2CH2CH2CH3
Hexane (69)
6
CH3CH2CH2CH2CH2CH3
Heptane (98)
7
CH3CH2CH2CH2CH2CH2CH3
Octane (126)
8
CH3CH2CH2CH2CH2CH2CH2CH3
Nonane (151)
9
Decane (174)
10 CH3CH2CH2CH2CH2CH2CH2
CH3 CH2 CH2CH2CH2CH2CH2Matter
CH2CH3
And
Measurement
CH
CH CH
2
2
3
Distillation of Hydrocarbons:
Petroleum Refinery Towers
0 C
120 C
200 C
250 C
300 C
Matter
And
Measurement
Separation by differences in ability to
form a gas (boiling points)
Mixture / Solution or
Pure Substance?
H2O vapor
Physical
Separation
Cu(NO3)2(s)
• Mixtures can be separated by differences in the physical
properties of the substances they are composed of. Matter
And
Measurement
• Pure substances cannot be separated by physical methods.
Separation by differential solubility,
filtration and evaporation
H2O vapor
Mixture: CdS (yellow, insoluble substance), Cu(NO3)2 (blue
soluble substance), H2O(clear liquid).
Matter
And
Measurement
(4) Chromatography: Separates substances on
the basis of their differences in their solubility in a
specific solvent.
Filter
paper
Substance to
be separated
(black ink)
Solvent: 50: 50
Water: Alcohol
{Paper Chromatography}
Matter
And
Measurement
Matter
And
Measurement
Heterogeneous
Classification of Matter
*
Cu(NO3)2
Mixtures
(Heterogeneous)
Physical
Homogeneous
Mixtures
Separation
Solutions
(Homogeneous)
Physical
Cu(NO3)2 (aq)
Separation
Cu(NO3)2 (s)
Compounds
Chemical
Decomposition
Elements
Pure
Substances
Matter
And
Measurement
Chemical Decomposition of
Pure Substances
• Cannot be separated by physical means.
• Composed of one substance only, which can be
either an element or a compound.
• Compounds can be broken down by chemical
means, elements cannot.
Examples of pure substances:
Gold (Au), Oxygen (O2), Water (H20), Methanol (CH3OH),
Table salt (NaCl)
Matter
And
Measurement
Each has its specific physical properties (m. pt., density, etc.)
Compounds
can be broken down into more elemental particles
(elements) by chemical decomposition reactions.
Electrolysis of Water:
2 H2O (l)
→
elect.
2 H2 (g)
+ O2 (g)
Matter
And
Measurement
{Electrolysis}
How do we get pure Sodium?
→ 2 Na
elect
2 NaCl (l)
(l)
+ Cl2 (g)
NaCl is electrolyzed in a Downs cell.
Matter
And
Measurement
Elements
cannot be broken down into more elemental particles
by ordinary chemical means.
Matter
And
Measurement
Classification of Matter
Heterogeneous
Physical
Mixture
Homogeneous
Separation
Physical
Separation
Solution
Chemical
Element
Decomposition Compound
Matter
And
{mixture
vs.
Measurement
compound}
Units
of
Measurement
length (m)
mass (g, kg)
volume (mL, L)
temperature (oC, oK)
time (s)
Matter
And
Measurement
Metric
System
When using
dimensional
analysis for metric
problems: always
consider the larger
unit as having a
value of 1, then
the smaller unit
would contain a
large multiple of
that unit.
Example: 1 m
compared to cm.
 0.01 m 


 1 cm 
 1m 


100
cm


SI Prefixes
Prefix
Symbol
Meaning
Multiplier
Multiplier
(numerical)
(exponential)
yotta
Y
septillion
1,000,000,000,000,000,000,000,000
1024
zetta
Z
sextillion
1,000,000,000,000,000,000,000
1021
exa
E
quintillion
1,000,000,000,000,000,000
1018
peta
P
quadrillion
1,000,000,000,000,000
1015
tera
T
trillion
1000,000,000,000
1012
giga
G
billion
1,000,000,000
109
mega
M
million
1,000,000
106
kilo
k
thousand
1,000
103
hecto
h
hundred
100
102
deka
da
ten
10
101
1
100
UNIT
X 1000
X 10
ONE
1
deci
d
tenth
0.1
centi
c
hundredth
0.01
milli
m
thousandth
0.001
micro

millionth
0.000 001
nano

billionth
0.000 000 001
10-9
pico

trillionth
0.000 000 000 001
10-12
femto

quadrillionth
0.000 000 000 000 001
atto

quintillionth
0.000 000 000 000 000 001
zepto
z ()
sextillionth
0.000 000 000 000 000 000 001
yocto
y
septillionth
0.000 000 000 000 000 000 000 001
10-1
X 10
10-2
10-3
X 1000
10-6
10-15
Matter
10-18
And
Measurement
10-21
10-24
Atomic Dimensions
Atoms
Tenth of a nanometer (10 -9 m)
Nuclei of atoms
Hundredth of a picometer (10 -12 m)
Protons & Neutrons
Fentometer (10-15 m)
Quarks & electrons
Attometer (10-18 m)
Matter
And
Measurement
Metric
Conversions
Always convert
PREFIXES to UNITS
(not PREFIXES to
other PREFIXES)
Example: Mm
compared to pm.
 1 Mm  1 m 

 12

1
,
000
,
000
m

 10 pm 
Factors, ratios,
equivalences.
Example: cm
compared to m.
 100 cm 


1
m


 1m
 6
 10 μm



SI Prefixes
Prefix
Symbol
Meaning
Multiplier
Multiplier
(numerical)
(exponential)
yotta
Y
septillion
1,000,000,000,000,000,000,000,000
1024
zetta
Z
sextillion
1,000,000,000,000,000,000,000
1021
exa
E
quintillion
1,000,000,000,000,000,000
1018
peta
P
quadrillion
1,000,000,000,000,000
1015
tera
T
trillion
1000,000,000,000
1012
giga
G
billion
1,000,000,000
109
mega
M
million
1,000,000
106
kilo
k
thousand
1,000
103
hecto
h
hundred
100
102
deka
da
ten
10
101
UNIT
meter, liter,
gram
ONE
1
100
deci
d
tenth
0.1
10-1
centi
c
hundredth
0.01
10-2
milli
m
thousandth
0.001
10-3
micro

millionth
0.000 001
10-6
nano

billionth
0.000 000 001
10-9
pico

trillionth
0.000 000 000 001
10-12
femto

quadrillionth
0.000 000 000 000 001
atto

quintillionth
0.000 000 000 000 000 001
zepto
z ()
sextillionth
0.000 000 000 000 000 000 001
yocto
y
septillionth
0.000 000 000 000 000 000 000 001
10-15
Matter
10-18
And
Measurement
10-21
10-24
Metric Conversion Problems
km
• How many pm are there in 0.0023 cm?
hm
L
 E 1 m   1012 pm 
7
? pm  0.0023 cm 



2
.
3
x
1
0
pm



dam
1 mile = 5,280 ft.
100 cm   1 m 
N
G
1 yd = 36 in.
T METER (m)
• Change 60. mphH to km/s. {Hint: 1 mi. = 1.6 km}
dm
3 ft. = 1 yard
1 min

  cm
 1.6 kmcm
  1 hr 2.54
=
1
in.
12 in. km
= 1 ft.
? km  60. mi

0
.
027






s
hr 1 mi  60 min   60 s 
s


mm
• How many m3 of water are there in 25 ft3 ?
12 in 3  2.54 cm 3  1 m  3

3
? m  25 ft 

0.71
m





 1 ft   1 in   100 cm 
3
3
Matter
And
Measurement
Volume: Liter (L)
and the milliliter (mL)
10 cm
10 cm
10
cm
 A liter is a cube 1 dm3 = 10 cm
long on each side.
1 L = dm3 = (10 cm)3 = (10 X 10 X 10) cm3 = 1000 cm3
= 1000 mL
or
1mL = 1/1000 L
Cubic centimeter
 A milliliter (mL) is a
cube 1 cm long on each
side.
1cm 3  1cc
 1mL
= milliliter
Matter
And
Measurement
Temperature: measure of the average kinetic energy *
(motion caused by heat) of the particles in a sample.
{K.E ∝ Temp}
T = change in temp
373
-273
100
K = C + 273.15
100
-0
100
212
- 32
180
C = (F − 32)
1.8
As KE increases
molecules vibrate more
and their volume
expands (Temp).
Matter
And
Measurement
F = 1.8(C) + 32
•
•
Measured vs Exact
Numbers
Measured Numbers:
(1) Accuracy & Precision
(2) Uncertainty
(3) Significant figures &
rounding-off
Exact Numbers: from formulas,
definitions & counting
For sphere
4  r3
V
3
1 mile = 5,280 ft
1 km = 1,000 m
Matter
And
Measurement
Measured Numbers:
Accuracy versus Precision
• Accuracy refers to the
proximity of a measurement to
the true value of a quantity.
• Precision refers to the
proximity of several
measurements to each other.
Matter
And
Measurement
Measured vs. Exact Numbers
Measured numbers are obtained
when a measuring instrument
(ruler, balance, thermometer) is
used to determine a physical
property of a substance.
The number of significant figures
these measurements contain
depend on the accuracy of the
instrument being used.
uncertainty
13.7
+0.1
7.63
+0.01
Matter
And
Measurement
uncertainty
Uncertainty in Measurements
Different instruments have different degrees of
accuracy, uncertainty is + 1 of estimated digit.
+0.1
+0.01
uncertainty
89.5 mL
2.65 mL
Matter
And
Measurement
Measured vs. Exact Numbers
METRIC
Exact Numbers
METRIC-ENGLISH
CONVERSIONS
ENGLISH
Exact Numbers
km
L
E
N
G
T
H
hm
dam
METER (m)
dm
cm
1 mile = 5,280 ft.
Measured Numbers
(1 in is exact, the 2.54
cm is measured)
2.54 cm = 1 in.
1 yd = 36 in.
3 ft. = 1 yard
12 in. = 1 ft.
mm
How many km are there in a Marathon (26 miles)?
Matter
And
 41.842944
km
Measurement
 5,280 ft   12in   2.54cm   1m   1km 
 


? km  26mi 
 

 1mile   1 ft   1 in   100cm   1000m   41.8 km
Significant Figures
• Significant figures refers to digits that were
accurately measured by an instrument.
Example: 220g, 220. g, 220.5g, 220.50g, 220.507g.
(all numbers above are measures of the same object, what is the
difference?)
accuracy
Matter
And
Measurement
Rules for determining the number of
Significant Figures
1. All nonzero digits (NZD) are always
significant.
2. Zeroes between NZD are always
significant. Ex: 103
3. Zeroes to the left of NZD are never
significant. Ex: 0.0103
4. Zeroes to the right of NZD are
significant if a decimal point is written
anywhere in the number. Ex. 0.01030
Matter
And
Measurement
Rounding-off
• Round-off your calculated numbers, to
the correct number of significant figures,
so we do not overstate the accuracy of
our answers.
Example: 23g + 23.632g = 46.632
= 47g
You cannot add an inaccurate measurement to a
accurate measurement and get and accurate answer.
Matter
And
Measurement
Significant Figures in
Addition & Subtraction
*
• When addition or subtraction is performed,
answers are rounded to the least significant
decimal place.
Example: add the following numbers
34
231.678
0.00354
265.68154
266
Matter
And
Measurement
*
Significant Figures in
Multiplication & Division
• Answers are rounded to the number of
digits that corresponds to the least
number of significant figures in any of
the numbers used in the calculation.
(29.2 – 20.0) = 9.2
Example: (29.2 – 20.0) (1.79 x 105)
1.39
Calculator answer = 1.1847482 x
Correct answer = 1.2 x 106
106
Matter
And
Measurement
Uncertainty in Measurements
• Piece of Black Paper – with rulers beside the edges:
Determine the Area of Black Paper!
Let’s look
more
accurately !
Area = Length x Width
Matter
And
Measurement
Uncertainty in Measurements
• Piece of Paper – Side A enlarged
– How long is the paper to the best of your ability to measure it?
13.6 cm
+ 0.1 cm
When using an instrument your last digit recorded should be a
significant digit estimated between the two smallest
Matter
Andbe
measurement lines of your instrument. Your precision would
Measurement
+ 1 of that digit.
Uncertainty in Measurements
• Piece of Paper Side B – enlarged
– How wide is the paper to the best of your ability to measure it?
7.63 cm
+ 0.01 cm
When using an instrument your last digit recorded should be a
significant digit estimated between the two smallest
Matter
Andbe
measurement lines of your instrument. Your precision would
Measurement
+ 1 of that digit.
Area of Paper
Area = 13.6 cm x 7.63 cm = 103.768 cm2
is the calculator answer.
104 cm2
Matter
And
Measurement
Density:
A Physical property of a substance,
defined as:
• Amount of matter (# atoms) per
unit volume = compactness.
• the mass divided by the volume.
D=
D Hg
m
V
Mass (g)
=
Volume (mL)
 13.5 g   1 mL
Matter 
 13.5g/mL can be used as a ratio : 
 or  And 
Measurement
g
 1 mL   13.5
Density and Temperature
Density: the mass of a
substance divided by its volume.
D  mass(g)
volume ( mL)
Temperature: a measure of
the amount of kinetic energy
(motion) an object possesses.
As the temperature
increases the volume
increases due to the
greater kinetic energy of
the atoms or molecules.
The mass is not affected.
Matter
And
Measurement
Density of water at various
temperatures
°C
°F
0.0
4.0
15.0
32.0
39.2
59.0
20.0
25.0
37.0
50.0
68.0
77.0
98.6
122.0
100.0
212.0
D in g/cm³
0.9998425
1.0000000
0.9991026
0.9982071
0.9970479
0.9933316
0.9880400
0.9583665
Matter
And
Measurement
*
Density Problems
For a Fe metal object whose density is 7.86 g/mL.
(a) What is the mass (g) of a piece of this metal if it displaces
12. mL of water in a graduated cylinder?
7.86 g 

?g  12 mL 
  94 g
 1 mL 
(b) What is the volume in mL of 34 kg of this same metal?
 1,000 g 
? mL  34 kg 

 1 kg 
 1 mL 

  4300 mL
 7.86 g 
Matter
And
Measurement
*
Density Problems
The density of Hg is 11.7 g/mL. What is it in kg/m3?
? kg
m3
 11.7 g
3
 1 kg   100 cm   11,700 kg/m3
 

mL 
 1000 g   1 m 
Matter
And
Measurement
Density of various substances
Density is directly
proportional to the
Molecular Weight of
a substance.
{DBr  MW}
Matter
And
Measurement