02 matter is atoms that move after class

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This is lecture 2, about the atomic nature of matter and Brownian motion.

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  • 1. Enroll clickers

2. Today: Some administrative stuff Matter is atoms, Brownian motion,Scanning tunneling microscopy

  • If you missed Tuesdays class
    • Do HW #1 on vista.unm.edu !!!
  • Next homework will be assigned tomorrow night,
  • due Tuesday before lecture (check WebCT)

3. WebCT Demo 4. What is Physics?

    • Physics is about the nature of basic things such as motion, forces, energy, matter, heat, sound, light, and the structure of atoms.
    • Our Textbook
    • Wikipedia
    • Physicsis thescienceofmatterand itsmotion , as well asspaceandtime thesciencethat deals with concepts such asforce ,energy ,mass , andcharge . Physics is anexperimental science , and it is the objective of physicists to understand how thenatural worldworks.

Physicsis thenatural sciencewhich examines basic concepts such asenergy ,force , andspacetimeand all that derives from these, such asmass ,charge ,matterand itsmotion . More broadly, it is the general analysis ofnature , conducted in order to understand how theworldanduniversebehave. 2008 2009 Students Tuesday Behavior of matter; How bodies interact; how stuff works; the law of motion; understanding chemistry; natural and unnatural force (manmade); 5. Brainstorming: Whats in this room?(If I dont hear, shout again!) A Dark matter Quarks Electrons heat B Molecules Atoms Oxygen CO2, H20 Neutrons, protons, steam C People/students Desk, chairs, lights, chalkboard, air, neutraphils, bacteria, thoughts, pheremones, dust, C A Dark energy Space-time, heat,B Light waves, sounds waves (waves), gravity, motion, interactionsC God, ideas, Jesus, thoughts, ___ual tension, physics 6. Brainstorming: Whats in this room?(If I dont hear, shout again!) A quarks Electrons Photons(waves?) B Oxygen, CO2, carbon Atoms & moleculesProtons neutrons C People, Electronics Materials (Furniture,shoes,sheets) Air, sensors A Heat, energy, Gravity, space-time B Light (radiowaves), sound, color, shadows, pressure, motion,C Electricity, smell Emotions Thoughts Mathematics Geometry Architecture physics Fundamental particles Complex materials Pure materials Fundamental abstract things Complex abstract things Complex abstract things ? 7. Brainstorming: Whats in this room?(If I dont hear, shout again!) A quarks Electrons Photons(waves?) B Oxygen, CO2, carbon Atoms & moleculesProtons neutrons C People, Electronics Materials (Furniture,shoes,sheets) Air, sensors There are many physics concepts here,and there is no way we can cover them in order! A Heat, energy, Gravity, space-time B Light (radiowaves), sound, color, shadows, pressure, motion,C Electricity, smell Emotions Thoughts Mathematics Geometry Architecture physics Fundamental particles Complex materials Pure materials Fundamental abstract things Complex abstract things Pure? abstract things 8. Powers of 10 video This video explores our universe in powers of 10 for length scales (i.e. 1 meter, 10 meters, 100 meters, 1kilometer, etc.) Its a bit old and hokey, but still pretty cool.It ends at the length scale well talk more about today: very small (atoms) Feynman apple 9. Clicker Question

  • If you put a drop of food coloring into a cup of corn sryup, what happens over course of time?
  • Drop stays exactly where it is
  • Drop slowly spreads out

Why? 10. Brownian motion as evidencefor existence of atoms It took over 80 years in 1800-1900s for scientists to become convinced about atoms 11. pollen grains jiggleperpetuallyin room temperature water Fluorescent microspheres (1/1000 thof a millimeter) in water tethered to slide with single DNA molecules Viewed through a microscope why are they jiggling??? 12. Overhead Brownian Motion Demo In this demo, we are looking at the shadows of small spheres being shaken by a motorized corral Q: What will happen when we add a bigger ball bearing to the medium-sized ones? A: It will move more slowly than the medium-sized ones B: It will move the same as the medium-sized ones C: It will move more quickly than the medium-sized ones Discuss with your neighbors 13. Brownian motion in surprising places! (Laser demo) In this demo, we will be using laser light (described later in course) and seeing what it looks like when we shine on dry versus wet paint Dry paint:Keep your head very still, then move head slightly back and forth. Q: What is paint made of? Q: What do you think will happen with the wet paint? 14. A few key points about Brownian motion

  • Atoms are not stationary!
  • Book misleads you, though overall diffusion is VERY slow.
  • The smaller things get, the more important is Brownian motion
  • Lets look at something small again Prof. Diane Lidke (UNM Pathology) movie (4)

15. Clicker Question

  • How is the below image made (similar to the book figure 11.5, iron atoms on cobalt)?
  • Computer simulation
  • Powerful light microscope (stereo)
  • By measuring electron current from a scanning sharp probe
  • Scattering electron waves

http://www.almaden.ibm.com/vis/stm/corral.html Discuss with your neighbors 16. Clicker Question

  • How is the below image made (similar to the book figure 11.5, iron atoms on cobalt)?
  • Computer simulation
  • Powerful light microscope (stereo)
  • By measuring electron current from a scanning sharp probe
  • Scattering electron waves

http://www.almaden.ibm.com/vis/stm/corral.html Brownian motion is indirect evidence of existence of atoms Scanning tunneling microscopy seems even more direct 17. Scanning Tunneling Microscopy http://www.ieap.uni-kiel.de/surface/ag-berndt/mikro/images/stm-320.jpg http://www.nrc-cnrc.gc.ca/multimedia/picture/images/html/nrc-nint_scan_tunn_mic-lr.jpg 18. STM can be used to build fun thingsone atom at a time http://www.almaden.ibm.com/vis/stm/corral.html Iron atoms on copper crystal Do you notice anything else in these images? 19. Structure of the atom Atom is composed of protons & neutrons in a dense nucleus Much less massive electrons orbit the nucleus in shells or clouds User:Yzmo on wikimedia commons 20. Clicker Question

  • Is an atom mostly solid or mostly empty space?
    • a) Solidb) Empty space

21. Clicker Question

  • Is an atom mostly solid or mostly empty space?
    • a) Solidb) Empty space

Stipe et al. Science279 , p.1907 Oxygen molecules on top of Silicon crystal (very cold!) Author of textbook says empty space Doesnt seemlike empty space to me 22. Check WebCT this weekend!!!

  • HW due Tuesday
  • Reading Tuesday / Thursday
  • Quiz due next Thursday