This preview shows page 1. Sign up to view the full content.
Unformatted text preview: s science, chemistry,
condensed matter physics...) and go straight to the
• Used to be, we’d say you can’t “see” atoms, but
now we can! (Atomic Force Microscopy) 4 Atoms can now be “imaged” Image of individual atoms in Mica (from www.di.com, Digital Instruments)
see also http://stm2.nrl.navy.mil/how-afm/how-afm.html
http://stm2.nrl.navy.mil/how-afm/how-afm.html 5 Early Evidence for Atoms
1800 John Dalton found that substances combine in
simple ratios of their weights,
eg: 2 grams of X for every 4 grams of Y,
or 1:1, 1:2, 1:3, 2:3,…
This is easy to understand if substances made of atoms
Eg Water H2O needs 2 atoms of Hydrogen for one of
Oxygen. If we call the mass of one atom of H 1 (atomic
mass unit) then Oxygen is 16, and ratio will be 2:16 = 1:8 6 iClicker Question
In Photosynthesis, CO2 and H2O combine. If (for
simplicity) we have one molecule of each, what is
the mass ratio?
H has mass 1 amu, C 12 amu, O is 16 amu a) 28:17, ie 28 amu of CO2 for each 17 of H2O
d) 1:1 7 Convincing evidence of atoms: Brownian Motion
Pollen grains (and all other...
View Full Document
This note was uploaded on 01/31/2014 for the course BILD 3 taught by Professor Wills during the Winter '07 term at UCSD.
- Winter '07
- The Elegant Universe