Transcript General and Inorganic Chemistry

General and Inorganic Chemistry
Introduction to Chemistry
What is Chemistry
 Chemistry is the study of chemicals; how
properties depend on composition. What
substances are and how they change.
 El Khemid - the transformation. Chemistry
is about changing substances into others.
 What chemicals? First metals then
cosmetics, medicines, ceramics, glass
making.
What did early chemists do?
 Identify, classify, describe; Knowledge
leads to curiosity.
 Rather than learn all substances seek
underlying patterns and theories that explain
chemical behavior.
 Apply scientific method.
Apply scientific method.
• Observation vs interpretation
 Observation - with statement of certainty is a fact
 Laws - generalized observations
 Hypothesis to explain observations - predictions
 Experiment - Test hypothesis
 Theory - tested hypothesis
 Model- Combination of theories that form a general
explanation of wide variety of phenomenon
A Delicate Balance
• Science is different from art in that
scientific knowledge requires agreement;
first of the facts and then of the theories.
• There is a delicate balance between what is
known and what we think about what is
known.
• This is the idea of provisional truth; we
believe our hypotheses but maintain a
healthy skepticism.
Serendipity
• "Chance favors the prepared mind”
• When asked “what did you think when you
saw the bones of your hand on the screen in
front of the cathode ray tube”? Roentgen
replied “I did not think. I investigated.
How do we describe matter?
• Matter occupies space and has weight.
(Actually Mass, weight is the affect of
gravity on mass).
• Matter exists in three physical states.
– Solid
– Liquid
– Gas
Properties of Matter
• Physical properties: Color, mp, bp, density,
index of refraction. Observation of these do
not change chemical composition.
• Chemical properties: Observation of these
causes a chemical change; substances
become other substances. Reactivity with
acids to liberate carbons dioxide.
Physical properties
• Physical properties can be:
• Extensive i.e. depend on amount of
substance like mass or volume
• Intensive i.e. independent of amount like
temperature or pressure.
• Some properties are qualitative others are
quantitative.
Quantitative properties.
• Measurements require a system of units
• SI- Systeme International
• Base units m, kg, s, K, mol
• Derived units: Joule, liter, pascal…
• Prefixes: mega, kilo, deci, centi, milli,
micro, nano, pico
conversions
1 in = 2.54 cm
1 m = 39.37 in
1 lb = 453.6 g
1 kg = 2.205 lb
1 qt = 946.4 mL
1 L = 1.057 qt
J = 1 kg m/s2
1 cal = 4.184 J
TF = 9/5 TC + 32
TK = TC + 273.15
Energy
•
•
•
•
Energy: ability to do work
Kinetic = mv2/2
Potential - chemical
Conservation of energy. Heat and work
transfer energy
Temperature: zeroeth law
• Heat is the flow of energy from a hot object
to a cold object.
• Heat flows from regions of high
temperature to regions of low temperature.
• Differentiate between heat which is energy
flow and temperature which gives the
direction of flow.
Accuracy and Precision
• An Advil  Tablet was "weighed" on a
digital laboratory balance 22 times with the
following results
No.
Mass
0.43
3
0.44
1
0.45
2
0.46
9
0.47
5
0.48
1
0.49
1
determination of mass
No.
10
Mass
0.43
3
0.44
1
9
8
7
2
0.46
9
0.47
5
0.48
1
0.49
1
6
freq
0.45
5
4
3
2
1
0
m ass/g
The normal distribution
mean= 0.4586
mean= 0.4586
, Standard
deviation
The normal distribution
67%
95%
Accuracy
systematic errors
Precision
random errors
Significant Figures
1. All non - zero digits and captured zeros ARE SIGNIFICANT:
6023 has four significant figures.
2.Zeros used only to position the decimal point are NOT
SIGNIFICANT:
0.0006023 has four significant figures.
3.If a result ends in zeros to the right of the decimal point
then those zeros ARE SIGNIFICANT. 2.200 has four significant
figures.
4.If a result ends in zeros not to the right of the decimal point
these zero ARE NOT SIGNIFICANT. 600 000 has only one
significant figure.
Every sample of a pure substance has the same
properties. In contrast the properties of mixtures
depend on the compostion of each sample
Matter
Substances
Mixtures
Homogeneous
Solutions
Heterogeneous
Colloids
Pure Substances
Elements
Metals
Solids
Non-metals
Liquids
Compounds
Molecular
Gases
Ionic
Mixtures can be separated into
their pure components
• Mixtures can be separated into their pure
components by physical means
–
–
–
–
–
Filtration
Mechanical separation
Distilation
Dissolving
Chromatography
Elements &Compounds
• Elements can not be broken down into
simpler substances
• Compounds can be chemically broken down
into the elements of which they are
composed.
• There are 108 elements known but 40 of
these compose 99.9% of all substances.
• 10 elements compose 99% of the earth’s
crust.
Ten elements compose 99% of the earth’s crust
Element
Oxygen(O)
Silicon(Si)
Aluminium(Al)
Iron(Fe)
Total
% Mass
49.1
26.1
7.5
4.7
87.4
Element
Calcium(Ca)
Sodium(Na)
Potassium(K)
Magnesium(Mg)
Hydrogen(H)
Titanium(Ti)
Chlorine(Cl)
Carbon (C)
others
% Mass
3.4
2.6
2.4
1.9
0.88
0.58
0.19
0.09
0.56
Water
Earth
Fire
Air
Element
Oxygen(O)
Carbon(C)
Hydrogen(H)
Nitrogen(N)
Total
% Mass
64.6
18.0
10.0
3.1
95.7
Three quarters of the elements are metals
Metals are:
•Ductile
The chemical symbols for
some metals are not the same
as the first letter of the English
name for the element:
•Lustrous
Pb-lead
•Conductors
K-potassium Cu-copper
•Malleable
•heat
Fe-iron
•electricity
Na-sodium
Sn-tin
W-tungsten
Hg-mercury
These non-metals are solids at room
temperature:
Arsenic-As
Phosphorous-P Sulfur-S
Iodine-I
Boron-B
Selenium-Se
Carbon-C
The rest are gases
The Law of Constant Composition
The relative amounts of each element in a
compound are always the same.
Mass percentage or percent composition
Mass of Element X 100
Mass of compound
Fe = 1.56 g
S= 0.9007g
2.47g
% massFe = 1.56/2.47 x100 = 63.5%