Transcript Introduction to chemistry

Introduction to Chemistry –
Background for Nanoscience
and Nanotechnology
Prof. Petr Vanysek
Introduction to Chemistry
Principles
Introduction to measurements
Introduction to measurements
Distance/size
dynamics of the scale – from the wavelength of
x-rays to astronomic distances.
focus on the “middle” scale size from visible
objects – person, hand (where did inch come
from?), fingernail thickness, hair diameter, mite,
microbe, virus, finally atom and a molecule.
Wide range of dimensions
Electromagnetic spectrum
Relevant dimensions:
kilometers (10+3 m)
meters
centimeters (2-1/2 = 1 inch)
millimeter
nanometers
Angstroms (10-10 m) – size of an atom
Atom:
Electrons going around
the nucleus
Units of Measurement
SI Units
• There are two types of units:
– fundamental (or base) units;
– derived units.
• There are 7 base units in the SI system.
Units of Measurement
Base SI Units
Units of Measurement
SI Units
Selected Prefixes used in SI System
Units of Measurement
SI Units
• Note the SI unit for length is the meter (m) whereas
the SI unit for mass is the kilogram (kg).
– 1 kg weighs 2.2046 lb.
Temperature
There are three temperature scales:
• Kelvin Scale
– Used in science.
– Same temperature increment as Celsius scale.
– Lowest temperature possible (absolute zero) is zero
Kelvin.
– Absolute zero: 0 K = -273.15 oC.
Measurements - Distance
Standard units:
length
Meter (a little more than 3 feet)
too large for some purpose
millimeter, centimeter
(multiples of 10, e.g., 1 meter = 1000 cm)
Inch – nonstandard unit, thumb (sp. thumb=pulgar,
inch=pulgada, greek inch=daktulos=finger)
Why dimensions matter?
Nanomaterials – particles of nanometer size
Nano-scale materials often have very different
properties from bulk materials
e.g. color and reactivity
• 3nm iron particle has 50% of atoms on the surface
• 10nm particle has 20% of atoms on the surface
• 30nm particle has 5% of atoms on the surface
The scale of things
Squared and cubed distance
Area = distance squared
Volume = distance cubed
the liter is a basic volume unit in chemistry, is is one decimeter cubed,
of 10x10x10=1000 cm cubed. It is somewhat larrer than one quart
Units of Measurement
Volume
• The units for volume
are given by (units of
length)3.
– SI unit for volume is 1
m 3.
• We usually use 1 mL
= 1 cm3.
• Other volume units:
– 1 L = 1 dm3 = 1000 cm3
= 1000 mL
Concentration
Amount per volume
grams per liter
moles per liter
Amount of material
mass – in kilograms or in grams
count of particles
12 = dozen
500 = ream
6.022 x 1023 = mole
Temperature
Vigor of movement of paticles – atoms or
molecules.
Scientific units – Degrees Celsius (water
freezes at zero and boils at hundred.
Kelvin – same spacing as Celsius, starts at
absolute zero and 0 oC is 273.15 K.
Change of volume with
temperature
Thermal expansion – volumetric thermal
expansion.
Mercury thermometer
Conversion of temperature units
Some units need to be converted, e.g.,
centimeters to inches, which is simple
multiplication.
Lcm = 2.54*Lin
Temperature conversiton Fahrenheit to
Celsius is a bit more involved
Tc = (5/9)*(Tf-32)
Tf = ((9/5)*Tc)+32
Large dynamic range of
dimensions
Forms of material
DIAMOND - GRAPHITE
Forms of material
CARBON - GRAPHITE
Form of material
GRAPHITE - FULLERENE
Fullerenes
Fullerenes
Acceptance of nanotechnology
Why Study Chemistry?
• Chemistry is the study of the properties of
materials and the changes that materials
undergo.
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• Chemistry is central to our understanding
of other sciences.
• It is substantial part of nanoscience and
nanotechnology
The Study of Chemistry
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The Molecular Perspective of Chemistry
Matter is the physical material of the universe.
Matter is made up of relatively few elements.
On the microscopic level, matter consists of
atoms and molecules.
Atoms combine to form molecules.
As we see, molecules may consist of the same
type of atoms or different types of atoms.
Molecular Perspective of
Chemistry
Classification of Matter
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States of Matter
Matter can be a gas, a liquid, or a solid.
These are the three states of matter.
Gases take the shape and volume of their
container.
Gases can be compressed to form liquids.
Liquids take the shape of their container, but
they do have their own volume.
Solids are rigid and have a definite shape and
volume.
Classification of Matter
Pure Substances and Mixtures
• Elements consist of a unique type of atom.
• Molecules can consist of more than one type of element.
– Molecules that have only one type of atom (an element).
– Molecules that have more than one type of atom (a compound).
• If more than one atom, element, or compound are found
together, then the substance is a mixture.
• Pure
Substances
and Mixtures
Classification of Matter
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Pure Substances and Mixtures
If matter is not uniform throughout, then it is a
heterogeneous mixture.
If matter is uniform throughout, it is homogeneous.
If homogeneous matter can be separated by physical
means, then the matter is a mixture.
If homogeneous matter cannot be separated by physical
means, then the matter is a pure substance.
If a pure substance can be decomposed into something
else, then the substance is a compound.
Classification of Matter
• Elements
• If a pure substance cannot be decomposed into
something else, then the substance is an
element.
• There are 114 elements known.
• Each element is given a unique chemical symbol
(one or two letters).
• Elements are building blocks of matter.
• The earth’s crust consists of 5 main elements.
• The human body consists mostly of 3 main
elements.
Classification of Matter
Elements
Classification of Matter
• Elements
• Chemical symbols with one letter have
that letter capitalized (e.g., H, B, C, N,
etc.)
• Chemical symbols with two letters have
only the first letter capitalized (e.g., He,
Be).
Classification of Matter
• Compounds
• If water is decomposed, then there will always be twice
as much hydrogen gas formed as oxygen gas.
• Pure substances that cannot be decomposed are
elements.
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Mixtures
Heterogeneous mixtures are not uniform throughout.
Homogeneous mixtures are uniform throughout.
Homogeneous mixtures are called solutions.
Properties of Matter
Physical vs. Chemical Properties
• Physical properties can be measure without changing the
basic identity of the substance (e.g., color, density, odor,
melting point)
• Chemical properties describe how substances react or
change to form different substances (e.g., hydrogen burns in
oxygen)
• Intensive physical properties do not depend on how much
of the substance is present.
– Examples: density, temperature, and melting point.
• Extensive physical properties depend on the amount of
substance present.
– Examples: mass, volume, pressure.
Properties of Matter
Physical and Chemical Changes
2 H2 + O2  2 H2O
Properties of Matter
Physical and Chemical Changes
• When a substance undergoes a physical change, its
physical appearance changes.
– Ice melts: a solid is converted into a liquid.
• Physical changes do not result in a change of
composition.
• When a substance changes its composition, it
undergoes a chemical change:
– When pure hydrogen and pure oxygen react completely,
they form pure water. In the flask containing water, there
is no oxygen or hydrogen left over.
Review of Chemistry
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States of Matter
Atoms, Molecules and Ions
Subatomic particles
Periodic Table
Covalent and ionic bonding
Chemical reactions
Inter-molecular forces
States of Matter
Solid
Keeps shape
Keeps
volume
Salt, gold,
copper
Liquid
Takes shape
of container
Keeps
volume
Water,
alcohol, oil
Gas
Takes shape
of container
Takes volume Air, argon,
of container
helium,
methane
Plasma – like
a gas of
charged
particles.
Takes shape
of container
Takes volume Stars, nebula,
of container
lightning,
plasma
reactors
Matter
• Solution: A uniform mixture of two substances
such that molecules are separate from each
other and move around randomly. Usually these
are liquids. Solutions are usually transparent.
• Colloids: A mixture of much larger particles
ranging from 20 nm to 100 μm. Milk and paint
are colloids.
• Grains: Some materials are made up of many
small crystals called grains. A grain is an
individual crystal of such a solid. Different grains
may have the crystal lattice oriented in different
directions.
Grain Structure in Steel
Elements, Atoms and Molecules
• Atoms: All matter is made up of tiny particles called atoms.
• Molecules: Sometimes two or more atoms are found bound together
to form molecules.
• The atoms can be categorized into about 115 different types based
on the charge of the nucleus.
• Elements are made up of only one type of atom.
• The element carbon takes the form of graphite, diamond and
buckminsterfullerene as well as others.
• It is only possible to change one type of atom into another through
nuclear processes such as take place in a nuclear power plant, the
sun, atomic bombs or particle accelerators.
• The elements do not change in ordinary chemical reactions.
The Periodic Table
1
H
2
He
3
Li
4
Be
5
B
6
C
7
N
8
O
9
F
10
Ne
11
Na
12
Mg
13
Al
14
Si
15
P
16
S
17
Cl
18
Ar
19
K
20
Ca
21
Sc
22
Ti
23
V
24
Cr
25
Mn
26
Fe
27
Co
28
Ni
29
Cu
30
Zn
31
Ga
32
Ge
33
As
34
Se
35
Br
36
Kr
37
Rb
38
Sr
39
Y
40
Zr
41
Nb
42
Mo
43
Tc
44
Ru
45
Rh
46
Pd
47
Ag
48
Cd
49
In
50
Sn
51
Sb
52
Te
53
I
54
Xe
55
Cs
56
Ba
57
La
72
Hf
73
Ta
74
W
75
Re
76
Os
77
Ir
78
Pt
79
Au
80
Hg
81
Tl
82
Pb
83
Bi
84
Po
85
At
86
Rn
87
Fr
88
Ra
89
Ac
104
Rf
105
Db
106
Sg
107
Bh
108
Hs
109
Mt
110
Ds
111
112
113
114
115
116
117
118
58
Ce
59
Pr
60
Nd
61
Pm
62
Sm
63
Eu
64
Gd
65
Tb
66
Dy
67
Ho
68
Er
69
Tm
70
Yb
71
Lu
90
Th
91
Pa
92
U
93
Np
94
Pu
95
Am
96
Cm
97
Bk
98
Cf
99
Es
100
Fm
101
Md
102
No
103
Lr
Subatomic Particles
Most of matter is made of three subatomic particles:
Particle
Symbol
Relative Relative Location
Charge Mass
Electron e-
-1
1
p+
+1
1836
Electron
Cloud
Nucleus
0
1839
Nucleus
Proton
Neutron n0
Ions
• Usually atoms have the same number of electrons as
protons so the charges cancel each other out.
• Sometimes an atom can have more or fewer electrons
than protons resulting in a net positive or negative
charge. When this happens it is called an ion.
• Example: Na loses an electron to form Na+
• Chlorine can gain an electron to from Cl• We can tell what type of charge an ion is expected to
have by looking at where it is in the periodic table.
Isotopes
• Atoms with the same number of protons
but different numbers of neutrons
• Deuterium, tritium, carbon 12, U235
• Some isotopes are radioactive while
others are stable