EPOD - a service of USRA
The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.
Atoms and Molecules
August 19, 2021
QuartzCrystals2021e
Photographer: Thomas McGuire
Summary Author: Thomas McGuire
The word atom originated thousands of years ago as a philosophical
idea that there might be a smallest division to every substance. It was
a concept with neither evidence nor application. But, in the early
1800s John Dalton observed that elemental substances combine in
consistent numerical ratios, which provided a scientific basis for the
idea of atoms. Still, this was indirect, non-observable evidence of
atoms. Regardless, Dalton’s discovery led to many useful principles in
chemistry.
There is, however, observational evidence of atoms in minerals.
Each of the characteristic shapes of mineral crystals can be attributed
to the spatial patterns of atoms and molecules. For example, quartz
(SiO ) can form beautiful six-sided crystals because of the way
atoms of silicon and oxygen join in hexagonal patterns, as
shown above in the picture and illustration.
You can also see evidence of irreducible units if you deposit a
small drop of a light, insoluble liquid such as oleic acid (the
principal ingredient of olive oil) on a water surface. The oil will
only spread out to a consistent limiting thickness before it breaks
apart. This experiment has two implications. First, it is more evidence
that there is some kind of irreducible unit of matter.
( Subatomic particles are beyond the scope of these kinds of
observations.) The second is that this is an indication of the diameter
of one of those units even though oleic acid (C H O ) is a
relatively large molecule. For comparison, oleic acid is 10^-9 m
compared to a hydrogen atom which is 10^-11 m.
Related EPODs
Atoms and Molecules Archive - Bonneville Salt Flats Panorama
Mount Etna – Eruption Plume and Scattered Lapilli Willow Falls
Near Hudson, Wisconsin Tower of Silence - Vermilion Cliffs National
Monument Volcanoes in New Mexico
More...
Geology Links
* Earthquakes
* Geologic Time
* Geomagnetism
* General Dictionary of Geology
* Mineral and Locality Database
* Mohs Scale of Mineral Hardness
* This Dynamic Earth
* USGS
* USGS Ask a Geologist
* USGS/NPS Geologic Glossary
* USGS Volcano Hazards Program
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Earth Science Picture of the Day is a service of the Universities
Space Research Association.
https://epod.usra.edu
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