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Unformatted text preview: eriments a
source of fascination, e
challenge. Chemistry is based on qualitative
observations and quantitative
Law of conservation of mass:
In a chemical reaction, the total mass of the
reactants must be equal to the total mass of
Law of conservation of energy: During any
process, energy is neither created not
destroyed. We need a common language and a
common set of units. (SI)
Compound units; e.g. density
“Answers” must have the appropriate units.
“Dimensional analysis” Intensive properties:
Independent of amount. e.g. density Extensive properties:
Dependent of amount. e.g. mass
Does not really apply at the nanoscale.
! CdSe nanocrystals In describing measurements, we need
to be cognizant of and sensitive to the
“accuracy” of a measurement or
result; i.e. how close are we to the
We often use “percentage error”.
We must also know what the precision
of a result is; i.e. reproducibility. (±?)
The precision is indicated by the
number of significant figures. By 2050 world energy needs will double!
Oil will be mostly depleted in next 50 to 60 years. How much is a Quad?
Need new energy sources and more efficient energy conversion & storage.
MThus, 100 Quadsnow!
ust start to plan is:
(Actually, we are already late.)
Courtesy: H. Kung @ DOE Atoms & Molecules
" All substances are either atoms or molecules (group of
atoms joined or “bonded” together).
" Any substance that cannot be broken down into
simpler substances is called an element.
" A substance that can be broken down is a compound.
" An element is a substance that consists only of atoms
with the same nuclear charge.
" Although ca. 120 elements; only 40 (or so) “really
count”. States of Matter Solid! Liquid! Gas! A solid has a fixed volume and a fixed shape.
A liquid has a definite volume but no specific
shape. (Takes the shape of the container.)
A gas fills the entire volume of its container and thus
has no definite shape. Liquid Crystals (4th state of matter)...
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This document was uploaded on 11/06/2013.
- Fall '12