From the Atom to the (i forgot) Flashcards
The (major) steps of the Big Bang:
1. ?
1. Universe in a singularity, energy and mass same thing VERY hot (and it cools)
The (major) steps of the Big Bang:
2. ?
- Matter-Antimatter ‘war’, matter won (somehow)
Gravity leaves
The (major) steps of the Big Bang:
3. ?
- Strong nuclear leaves
The (major) steps of the Big Bang:
4. ?
- All four forces split
Sea of radiation (fundamental particles)
Too hot for nucleons to form
The (major) steps of the Big Bang:
5. ?
- Protons and neutrons form
Sea of radiation still
The (major) steps of the Big Bang:
6. ?
- Atoms (deuterium) can now form (nucleosynthesis)
Deuterium can also form helium
The (major) steps of the Big Bang:
7. ?
- Light is seen (photons trapped in matter)
Stars, planets and galaxies can now form
Evidence for the Big Bang?
- Cosmic background radiation
- Expanding universe
- 75% hydrogen, 25% helium
- Formation of stellar structures
Evidence for expanding universe by Hubble?
- Red shift of elements compared to lab results
2. Estimation of distance with luminosity
What do the two axes on a H-R diagram represent?
Luminosity
Temperature
What is the order of temperature in a H-R diagram?
OBAFGKM
hottest) Oh Be A Fine Girl Kiss Me (coolest
Where do 90% of all stars lie?
The Main Sequence
Stars with greater mass are brighter because?
To counter the great mass they have, they need more energy which makes them bigger and brighter
Above the Main Sequence, there are?
Giants and supergiants
Below the Main Sequence, there are?
Dwarves
The steps of star formation:
1. ?
Hydrogen gas clusters
The steps of star formation:
2. ?
Gas contracts into dark cloud
The steps of star formation:
3. ?
Gravity potential converted into heat (eventually nuclear reactions)
Protostar forms and the mass spins
The steps of star formation:
4. ?
Fusion starts
Debris gets knocked off
The steps of star formation:
5. ?
Main sequence star is formed
What is stellar equilibrium?
The balancing of the force of energy pushing out and the gravity pushing in for stability
What is a common feature between all main sequence stars?
They use hydrogen (proton-proton) fusion whereby 4 protons form helium and energy
What are the two types of fusion possible by main sequence stars?
- Proton-proton chain
- CNO cycle (for stars hotter than 1.8x10^7)
The steps of star death (for x < 8 SM):
1. ?
Small, duller, yellowish, warm sun (like ours)
- proton-proton fusion
The steps of star death (for x < 8 SM):
2. ?
Red giant
- helium fusion (when hydrogen depletes)
The steps of star death (for x < 8 SM):
3. ?
Helium flash
- will have hydrogen, helium, carbon-oxygen core
- star contracts into core and expands
The steps of star death (for x < 8 SM):
4. ?
White dwarf (and planetary nebula)
- oxygen and carbon core
- cannot fuse (not hot enough)
The steps of star death (for x > 8 SM):
1. ?
Big, bright, blue, hot sun
- CNO cycle
The steps of star death (for x > 8 SM):
2. ?
Red giant
- core (from out to in): helium, carbon, oxygen, neon, silicon, iron
The steps of star death (for x > 8 SM):
3. ?
Supernova
- Star contracts and then explodes
The steps of star death (for x > 8 SM):
4. ? (for core mass < 1.4 SM)
Neutron Star
- Very dense, composed completely of neutrons
The steps of star death (for x > 8 SM):
4. ? (for core mass > 1.4 SM)
Black hole
- Single point of infinite density (singularity)
What were the 6 William Crookes’ observations about the cathode rays?
- Can appear from any surface
- Green fluorescent light
- Travel in straight lines
- Deflected by magnets
- Has energy and momentum
- Can cause chemical reactions
What did the Maltese Cross prove?
Cathodes travel in straight lines i.e. don’t diffract
they are particles not waves (for now…)
What did the Paddle Wheel prove?
They have energy and momentum
What did J.J. Thompson figure out with cathode rays and how?
the charge:mass ratio q/m using qvB = mv^2/r with electric and magnetic fields
What model of the atom did J.J Thompson make?
Plum pudding model, where the electron ‘plums’ were in a sort of positive ‘dough’
What did Milikan figure out with q/m?
The charge and thus mass of an electron, by making mg = qE with terminal velocity of an oil driblet (and v depended on mass and radius),
He concluded that charge is quantised
What was the Thompson model supposed to predict that?
The deflections would be minimal due to the whole atom being in positive and pass straight through as the charges (of the atoms) cancelling out would be too weak to affect the alpha particles
What did the Gold Foil Experiment show?
Most alpha particles went through the foil but 1/8000 got deflected over 90°
What model of the atom did Rutherford make?
Rutherford model, where the atom is mainly empty space that has electrons floating around and a tiny dense positive nucleus
What were the issues with the Rutherford model?
- Rutherford did not know how the electrons were arranged around the nucleus
- Rutherford did not know how the electrons moved without creating EMR and losing energy
- Rutherford did not know how the electrons did not collapse into the positive core
The unknown neutral radiation was thought to be gamma, why was it concluded it wasn’t?
Because it could knock protons off of paraffin wax which photons couldn’t do (i.e. it had mass and momentum)
Which two laws of conservation did Chadwick use to find the neutron?
- Momentum (since the proton mass ≈ neutron mass)
- Energy (since it’s elastic, velocity in ≈ velocity out)
Why was the paraffin wax used?
Neutrons could not be detected because they didn’t have a charge while protons (from the wax) could be
What did the inclusion of the neutron in the model of the atom achieve?
- Explained the extra mass of the atom
- Explained how electrons do not fall into the centre (as charges cancel out)
For the Balmer Formula, wavelength of emitted UV photon,
nf = 1 and ni = ?
ni = 2, 3, 4…
For the Balmer Formula, wavelength of emitted UV photon,
nf = ? and ni = 2, 3, 4…
nf = 1
For the Balmer Formula, wavelength of emitted visible photon,
nf = 2 and ni = ?
ni = 3, 4, 5…
For the Balmer Formula, wavelength of emitted visible photon,
nf = ? and ni = 3, 4, 5…
nf = 2
For the Balmer Formula, wavelength of emitted infrared photon,
nf = 3 and ni = ?
ni = 3, 4, 5…
For the Balmer Formula, wavelength of emitted infrared photon,
nf = ? and ni = 3, 4, 5…
nf = 3
What model of the atom did Bohr make?
Bohr Model:
- Electrons are situated around nucleus in ‘stationary states’
- Electrons absorb energy and move up state
- Electrons emit photon and move sown state
- Angular momentum is quantised (nh/2π)
Which two important pieces of information did Bohr use for his model?
- Planck’s quanta
- Balmer equation
- Other data