The Structure of Matter because you can’t understand how it works until you have some - PowerPoint Presentation

Slide1

The Structure of Matter

because you can’t understand how it works until you have some small idea of what it is…

http://scaleoftheuniverse.com/Slide2

In the past I never really taught much of this stuff…

So why start now?

With the probable discovery of the

Higg’s

Boson (a.k.a. The God Particle, or the G.D. Particle depending on the reference you choose) during the summer of 2012, it is apparent to me that young people should not be leaving high school without at least a very small notion of the modern understanding of the elements that make up matter.Slide3

Clearly this is not the realm of biology (life science) and while most good chemists admit that their field is really a specialty of atomic physics, chemistry stops right there: at the atom.

Physics is so broad and encompassing that the discussion of matter is really just a small, but increasingly important, aspect of the whole science.Slide4

Particle Physics: The structure of stuff

Let’s start with the atom…

About 130 years ago atoms were considered “fundamental.”

T

hat is to say that they were thought to be the smallest, most elementary pieces of matter possible.

Image of a uniform surface

from a scanning-tunneling

(electron) microscopeSlide5

Around 1880 theoretical models of the atom are born to help scientists understand other physical phenomena, particularly electromagnetism and radioactive decay

So we enter the realm of the “sub-atomic” particles: the electron, the proton, (and much later) the neutron.Slide6

Electrons

Discovered by J.J. Thompson and colleagues in 1897, Thompson produced the first known measurements of the particle: It’s charge to mass ratio (

e

/m). The actual charge of the

electon

(and therefore its mass using Thompson’s data) was discovered by Robert

Milikan

in 1909 in his famous “Oil Drop” experiment.Interestingly the electron is still considered a fundamental particle, belonging to a class known as leptons.Slide7

Protons & Neutrons

Lots of back history here, but most important:

Discovery of the nucleus, Rutherford, Gold Foil Experiment, 1911

Nuclear charge = atomic number, Van den

Broek

& Moseley, 1913

Isolation of a proton via low energy nuclear reaction, Rutherford, 1917

Conceived by Rutherford in 1920, Neutron discovered in 1932 by James Chadwick to explain specific nuclear phenomenaLater recognized as a key component in thermonuclear processes

Important thing: Protons and Neutrons are no longer considered fundamental!Slide8

So where do we go from here?

Lots of history between 1932 and the present, but I will sum up:

Lots of experiments with nuclear reactions both high energy (blowing stuff up) and lower energy (turning one type of atom into another)

Lots of experiments where electromagnetic forces are used to accelerate, or speed up, particles or even whole nuclei to ridiculous speeds and smash them into each other or other things.Slide9

What did we find out?

Lots of stuff but most importantly:

There appear to be 4 unique types of forces that affect matter. We will look at these “fundamental forces” later in this course.

We appear to have isolated a large but finite number of “fundamental particles” and amassed a great deal of knowledge about how they work together to comprise matter as we know it.Slide10

Fundamental Particles: Stuff which can’t be broken apart any further (maybe)

Quarks

Leptons

Force Carriers

This is about categorization people!

Don’t just try to memorize this stuff, work out a way to fit it together.

Even I get these twisted up sometimes.

I’ll give you some graphics at the end that will help.

Fermions (basically they follow the Pauli Exclusion Principle)Slide11

Quarks: Stuff that makes up “nucleons”

Quarks are fundamental particles which combine in a variety of ways forming composite particles known as

hadrons

and

mesons

.

You are familiar already with the most stable hadrons

: The proton and neutron.Slide12

Properties of Quarks

Fermionic

Spin ½

Carries electric charge (values depend on the type of quark)

Carries “Color Charge,” an interactive property (like electric charge, but completely different) that determines how quarks will align with other quarks

6 types: Up, Down, Charm, Strange, Top, Bottom

Type is determined by the quantum properties of the quark (above)

Anti-quarks exist for each of these (same absolute values but opposite signs for some properties).

Participate in all 4 fundamental force interactionsSlide13

Hadrons

Baryons:

3 quarks, generally 2 “regular” quarks and 1 anti-quark, or 2 anti’s and 1 regular.

Proton and Neutron are most common and stable

Full List:

http://en.wikipedia.org/wiki/List_of_baryons

Mesons:

2 quarks: 1 regular, 1 antiExotic, not common in normal matter, very short half-lives

Low energy mesons believed to participate in the nuclear (or “strong”) force process that holds the nucleus togetherHigh energy mesons believed to have played a role in the Big Bang, not normally associated with matter outside of high energy particle collisions in laboratory experimentation

You really need to be careful how you spell that, lest you say awkward things…Slide14

Leptons: Think “electron”

According to

wikipedia

, which has a nice article on the subject,:

A

lepton

is an elementary particle and a fundamental constituent of matter. The best known of all leptons is the electron which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties. Two main classes of leptons exist: charged leptons (also known as the

electron-like leptons), and neutral leptons (better known as neutrinos). Charged leptons can combine with other particles to form various composite particles such as atoms, while neutrinos rarely interact with anything, and are consequently rarely observed.Slide15

Charged Leptons

Electron,

Muon

, Tau particle

Anti-particles exist of each type

Muon

and Tau particles are rare in normal conditions, but have been substituted for electrons to form exotic atoms through various reactions.Slide16

Uncharged Leptons

Neutrinos

(electron neutrino,

muon

neutrino, tau neutrino)

Neutral charge

Very little mass (even compared to electrons)Rarely interact with matter

First theorized/observed associated with unexplained energy loss during beta-decay process.Slide17

Lepton Properties (all types)

Fermionic

Spin 1/2

Electric charge

NO color charge (unlike quarks)

Do NOT participate in the strong (nuclear) force, but are affected by other forces.Slide18

Fundamental Forces

1) Gravitational Force: Interaction between masses. Any object with mass is attracted to other masses by the gravitational force.

2) Weak Interaction: A sub-atomic force that occurs most often during nuclear beta decay.

3) Electromagnetic Force: A force between charged objects or particles. Any object with a charge is attracted or repelled by other charges depending on the sign of the charge.

4) Strong (Nuclear force): An attractive force that holds nucleons (protons/neutrons) together. Slide19

Force carriers

How does stuff react (know to move) as a result of other stuff?

Think about it: How does an electron repel from a nearby electron?

There is a LOT going on in this deceptively simple question, but the short answer is that fundamental particles exchange energy and therefore do work on each other through these fundamental force charge carriers

Also called Gauge BosonsSlide20

Types

Photons

Fancy name for electromagnetic radiation, everything from radio waves, to gamma rays with light and everything else in between can be called a photon.

These are the force carrier associated with the electromagnetic force and thus the primary mode of force transmission between leptons, but is also seen between charged

hadrons

.

So how does that electron (lepton) know that other electron (lepton) is out there and

they should repel? Answer: They shoot beams of light at each other.Slide21

Gluons

These particles allow for the communication of force between quarks.

Gluons are considered responsible for the strong force. They are the “glue” that keeps the nucleus of an atom from ripping apart.Slide22

W & Z Bosons

Unlike many of these particles, bosons are not

fermionic

, meaning the same type of particle with the same energy and properties can occupy the same space at the same time. Let that sink in for a moment.

Responsible for the “weak force”

Associated with the emission and absorption of neutrinos from and into matterSlide23

Higgs Boson

Proposed in 1964 and discovered* in 2012, the Higgs Boson is associated with the mechanism by which particles acquire mass and therefore by which gravitation affects matter

Zero charge, zero spin, zero color, approx. 126 times more massive than a proton, lifetime: about 1

zeptosecondSlide24

Putting it all together

Here’s a pretty good article that may help:

http://abyss.uoregon.edu/~js/ast123/lectures/lec07.html

The standard model of particle physicsSlide25

An overview of the various families of elementary and composite particles,

and the theories describing their interactions

Important for your test

Important so you are not scientifically illiterate

Important for your test