Transcript CHEMISTRY The Molecular Science Chapter one

CHEMISTRY
The Molecular Science
Chapter one
Slides prepared by
S. Michael Condren
Department of Chemistry
Christian Brothers University
to Accompany
CHEMISTRY The Molecular Science
by John W. Moore, Conrad Stanitski, & Peter C. Jurs
Chapter 1
The Nature of Chemistry
Matter
• has mass
• mass vs. weight
• occupies space
Chemistry
• The study of matter and the changes it can
undergo
Molecular Medicine
Scientific Method
• observations
– facts
• natural law
• model
– predictions
– hypothesis
• theory
– experiments to test the theory
Properties of Matter
Extensive Property
• depends on specific
sample under
investigation
• examples:
– mass and volume
Intensive Property
• identical in all samples
of the substance
• examples:
– color, density, melting
point, etc.
Properties of Matter
Physical Property
• one that can be observed without changing
the substances present in the sample
Temperature
Scales:
• Fahrenheit
• Celsius
• Kelvin
– absolute scale using Celsius size degree
Three Temperature Scales
Fahrenheit
Boiling Point of Water
Normal Body Temp.
Melting Point of Water
Absolute Zero
Celcius
Kelvin
212
100
373
98.6
37
310
32
0
273
- 459
- 273
0
Comparison of Temperature
Scales
Fahrenheit
Celcius
98.6
37.0
comfort temp. 68.0
20.0
bp water
212
100
mp water
32
0
bp - mp
180
100
body temp.
Temperature Relationships
C = 100/180  (F - 32) = 5/9  (F - 32)
F = (180/100)  C + 32 = (9/5)  C + 32
K = C + 273.15
- 40 F = - 40 C
Density
• Mass per unit of volume
density = mass/volume
d = m/V
Problem Solving by
Factor Label Method
• state question in mathematical form
• set equal to piece of data specific to the
problem
• use conversion factors to convert units of
data specific to problem to units sought in
answer
Exact Numbers
• conversion factors
• should never limit the number of significant
figures reported in answer
12 inches = 1 foot
Example
How many kilometers are there in 0.200
miles?
state question in mathematical form
#km
Example
How many kilometers are there in 0.200
miles?
set equal to piece of data specific to the
problem
#km = 0.200 miles
Example
How many kilometers are there in 0.200 miles?
• use conversion factors to convert units of data
specific to problem to units sought in answer
• solve mathematics
#km = (0.200miles)  (5280ft/mile)  (12in/ft)
 (2.54cm/in)  (1m/100cm)  (1 km/1000m)
= 0.322 km
3 sig. fig.
exact numbers
Properties of Matter
Chemical Property
• the tendency to react and form new
substances
Chemical Reaction
• reactants undergo chemical change to
produce products
sucrose => carbon + water
reactant
products
Chemical Change: carmelizing sugar
Chemical Reaction
Reactions are indicated by:
• evolution of a gas
• change of color
• formation of a precipitate
Pure Substances
Elements
Compounds
Mixtures
two or more pure substances
Heterogeneous
• uneven texture
Homogeneous (Solution)
• sample uniform throughout
Scheme for the Classification of Matter
Physical Changes
• changes in physical properties of
substances
Physical States
• solid
– fixed volume and shape
• liquid
– fixed volume
– shape of container, horizontal top surface
• gas
– takes shape and volume of container
Separation of Mixtures
• Filtration
• distillation
• chromatography
Filtration
• separate solids by differences in melting
points
• separate solids by differences in solubility
(fractional crystallization)
Distillation
• separation by differences in boiling point
(fractional distillation)
– distillate
– distillation
• fractionating column - part of apparatus where
separation occurs
Chromatography
•
•
•
•
•
•
liquid-column
paper
thin-layer (TLC)
gas
HPLC
electrophoresis (DNA mapping)
Sample Sizes
• macroscale
– physical properties that can be observed by the
unaided human senses
• microscale
– samples of matter that have to be viewed with a
microscope
• nanoscale
– samples that are at the atomic or molecular
scale where chemical reactions occur
Macroscale, Microscale, and Nanoscale
Kinetic Molecular Theory
Matter consists of particles (atoms or molecules) in
continuous, random motion.
Kinetic Molecular Theory: Solid
• particles are tightly packed together in regular
array
• particles vibrate about average positions
• seldom squeeze past other atoms
• results in a rigid material with a small, fixed
volume for a given mass
• external shape often reflects internal arrangement
of particles
Kinetic Molecular Theory: Liquid
• particles are arranged more randomly than in solid
• particles less confined so that they can move past
one another
• particles are a little further apart, thus slightly
larger, fixed volume
• particles are constantly interacting with one
another
Kinetic Molecular Theory: Gases
• particles in continuous, random, rapid motion
• collisions between particles are elastic
• volume occupied by the particles is negligibly
small effect on their behavior
• attractive forces between particles have a
negligible effect on their behavior
• gases have no fixed volume or shape, take the
volume and shape of the container
Nanoscale representations of the
three states of matter
Laws Known by Dalton
Law of Conservation of
Matter
• In an ordinary
chemical reaction
matter is neither
created nor destroyed.
• The sum of the masses
of the reactants equals
the sum of the masses
of the products.
Law of Constant
Composition
• A chemical compound
always contains the
same elements in the
same proportions by
mass.
Dalton’s Atomic Theory
Proposed in 1803
Postulate 1
• An element is composed of tiny particles
called atoms.
• All atoms of a given element show the same
chemical properties.
Dalton’s Atomic Theory
Postulate 2
• Atoms of different elements have different
properties.
Dalton’s Atomic Theory
Postulate 3
• Compounds are formed when atoms of two
or more elements combine.
• In a given compound, the relative number
of atoms of each kind are definite and
constant.
Dalton’s Atomic Theory
Postulate 4
• In an ordinary chemical reaction, no atom
of any element disappears or is changed into
an atom of another element.
• Chemical reactions involve changing the
way in which the atoms are joined together.
Law of Multiple Proportions
• the same elements can be combined to form
different compounds by combining the
elements in different proportions
Types of Elements
metals
nonmetals
metalloids – semimetals
Elements, Compounds, and Formulas
Elements
• can exist as single atoms or molecules
Compounds
• combination of two or more elements
• molecular formulas for molecular
compounds
• empirical formulas for ionic compounds
Allotropes
Oxygen
• diatomic oxygen, O2
• ozone, O3
Carbon
• diamond
• graphite
• Buckminsterfullerene
Risks and Benefits