02 Matter Is Atoms That Move After Class

Enroll clickers

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

If you missed Tuesday’s classDo HW #1 on vista.unm.edu !!!

Next homework will be assigned tomorrow night,

due Tuesday before lecture (check WebCT)

WebCT Demo

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

WikipediaPhysics is the science of matter and

its motion, as well as space and time— the science that deals with concepts such as force, energy, mass, and charge. Physics is an experimental science, and it is the objective of physicists to understand how the natural world works.

Students Tuesday

Behavior of matter; How bodies interact; how stuff works; the law of motion; understanding chemistry; natural and unnatural force (manmade);

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its motion. More broadly, it is the general analysis of nature, conducted in order to understand how the world and universe behave.

2008

2009

Brainstorming: What’s in this room? (If I don’t hear, shout again!)

ADark matter

QuarksElectrons

heat

BMolecules

AtomsOxygen CO2, H20

Neutrons, protons, steam

CPeople/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, interactions

C’God, ideas, Jesus, thoughts, ___ual tension, physics

Brainstorming: What’s in this room? (If I don’t hear, shout again!)

AquarksElectronsPhotons(waves?)

BOxygen, CO2,

carbonAtoms &

molecules Protons

neutrons

CPeople,ElectronicsMaterials (Furniture,shoes,sheets)Air, sensors

A’Heat, energy, Gravity, space-time

B’Light (radiowaves), sound, color, shadows, pressure, motion,

C’Electricity, smellEmotionsThoughtsMathematicsGeometryArchitecturephysics

Fundamental particlesComplex materials

“Pure” materials

Fundamental abstractthings Complex abstract

things

Complex abstractthings

?

Brainstorming: What’s in this room? (If I don’t hear, shout again!)

AquarksElectronsPhotons(waves?)

BOxygen, CO2,

carbonAtoms &

molecules Protons

neutrons

CPeople,ElectronicsMaterials (Furniture,shoes,sheets)Air, sensors

There are many physics concepts here, and there is no way we can cover them in

order!

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, smellEmotionsThoughtsMathematicsGeometryArchitecturephysics

Fundamental particles

Complex materials

“Pure” materials

Fundamental abstractthings Complex abstract

things

“Pure?” abstractthings

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.)

It’s a bit old and hokey, but still pretty cool. It ends at the length scale we’ll talk more about today: very small (atoms)

Feynman apple

Clicker Question

If you put a drop of food coloring into a cup of corn sryup, what happens over course of time?

a) Drop stays exactly where it isb) Drop slowly spreads out

Why?

Brownian motion as evidence for existence of atoms

It took over 80 years in 1800-1900’s for scientists to become convinced about

atoms

“pollen grains” jiggle perpetually in room temperature water

TIR Illumination

Magnetic Beads

Computer ControlledElectromagnet

Magnetic FieldGradient ForceF

Single moleculetether (e.g. DNA)

CCD CameraNon-magnetic Aspheric

ScatteredEvanescent Light

TIR Illumination

Magnetic Beads

Computer ControlledElectromagnet

Magnetic FieldGradient ForceF

Single moleculetether (e.g. DNA)

CCD CameraNon-magnetic Aspheric

ScatteredEvanescent Light

Fluorescent microspheres (1/1000th of a millimeter) in watertethered to slide with single DNA moleculesViewed through a microscope…why are they jiggling???

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 onesB: It will move the same as the medium-sized onesC: It will move more quickly than the medium-sized onesDiscuss with your neighbors

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 paintDry 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?

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 motionLet’s look at something small againProf. Diane Lidke (UNM Pathology) movie (4)

Clicker Question

How is the below image made (similar to the book figure 11.5, iron atoms on cobalt)?

a) Computer simulationb) Powerful light microscope (stereo)c) By measuring electron current from a scanning sharp

probed) Scattering electron waves

http://www.almaden.ibm.com/vis/stm/corral.html

Discuss with your neighbors

Clicker Question

How is the below image made (similar to the book figure 11.5, iron atoms on cobalt)?

a) Computer simulationb) Powerful light microscope (stereo)c) By measuring electron current from a scanning sharp

probed) 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

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

STM can be used to build fun things one 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?

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

Clicker Question

Is an atom mostly solid or mostly empty space?a) Solid b) Empty space

Clicker Question

Is an atom mostly solid or mostly empty space?a) Solid b) Empty space

Author of textbook says empty space…

Doesn’t seem like empty space to me

Stipe et al. Science 279, p.1907

Oxygen molecules on top ofSilicon crystal (very cold!)

Check WebCT this weekend!!!

HW due TuesdayReading Tuesday / ThursdayQuiz due next Thursday