Download PRESENTATION: Evolution of the elements through the lifecycles of

PRESENTATION: Evolution of the elements through the lifecycles of stars.
Josh Laeder
CONTENT TO BE TAUGHT: How Chemical Elements are formed throughout the life cycle of a star.
GLE'S/PERORMANCE EXPECTATIONS: 9-11 ES1A: Stars have life cycles. During most of their
lives, stars produce heavier elements from lighter elements starting with the fusion of hydrogen to form
helium. The heaviest elements are formed when massive star “die” in massive explosions.
OBJECTIVE(S): Given that elements are formed through nuclear fusion within a star and nuclear
recombination upon a stars death, the student will be able to fill out a graphic organizer depicting the
progression of nuclear fusion within a star until the point of the stars death. The student will be able to
explain in their own words why stellar death occurs at different points in a stars life cycle and what
elements could possibly be created.
MATERIALS NEEDED: 12 Balloons to depict various elements and events in the life cycle of a star.
Several pictures to depict drastic stellar events. Graphic organizer handout, with supplemental
questions. Marble, Bouillon cube.
ACADEMIC ENGLISH:
ACCOMMODATIONS:
PROCEDURES:
The Big Bang;
-For 1 to 3 seconds no nucleosynthesis can occur.
-Protons and Neutrons exist at a ratio of 50/50 but are outnumber by photons and electrons by 1Bill to 1
-It’s so hot that elements cannot form because photons are bashing into newly created nuclei.
-Finally at about 3-4 minutes the universe has expanded and cooled enough that protons and neutrons can unite
and form the most basic of elements.
-Deuterium (simplest form of H), -Tritium (H3) – Helium 3, Helium 4
-These most simple elements are formed because they are the simplest. The rate of immense heat cooling down
quickly due to great expansion of the universe only allowed these simple one and two proton elements to form.
-Trace amounts of Lithium and Beryllium also formed, elements 3 and 4, but in insignificant amounts.
- The universe is now at 92% H and 8% He, by volume. By atomic measurement it is 75%H and 25%He
because it takes 4H atoms to fuse in to He.
Star creation:
-Now we have vast clouds of Hydrogen and Helium that really want to come together, because gravity is in
charge.
-The universe expanded unevenly so different size stars and galaxies will form from these differently dispersed
clouds of H and He.
-Once enough Hydrogen has condensed that temperatures reach ~ 20Million K, Hydrogen will ignite and begin
to fuse into He.
Progression of elements within stars: As depicted with balloons
-Explain the theory of nuclear fusion creating outward pressure that balances with the inward force of gravity to
maintain a relatively homeostatic star.
-H-He. In our sun about 16 mill K, at 250 bill atmospheric pressure.
-He-C. 200Mill K. A huge jump.
-C-O. 800Mill K. At this points our star is about done. It will expand into a red giant and consume Mercury and
Venus. Once it reaches this size it will collapse upon itself and form a white dwarf. 1/millionth its normal size,
becoming ~ the size of earth.
-Stars that have 1-4 times our suns solar mass will most likely have this fate. A faint white star,
radiating with latent heat, comprised mainly of Carbon and Oxygen, but without fusion that will continue to glow
for millions of year.
-Larger stars will progress through the formation of several more elements through nuclear fusion.
-O-Ne. 1.5Bill K.
-Ne-Mg. 2Bill K.
-Mg-Si. 2.5 Bill K.
-Si-Fe. 3 Bill K.
-Once Fe has been fused in the center of a star it is near its end.
-Along this journey the first 26 elements up to Iron have been formed, but the primary fusion process has been
outlined above.
-Once the Iron in the core of a star has reached a relative density of 100,000 Kg per cm3, the star has reached a
point of critical mass and will explode into a supernova. (Hold up my 100 metric ton Bouillon cube).
-A star will not fuse iron because it has the most stable nucleus of all the elements. If you fuse iron it will absorb
energy rather than release it, therefore aiding gravity in its own collapse, rather than fighting it through nuclear
expansion.
-Stars with a mass of 20 times our sun could collapse to the point of black holes or neutron stars, but that is a
story of its own.
Supernova Explosion: Neutron Flux, Very Theoretical
-Picture striking a rubber ball on the ground with a hammer. It will compress, but eventually expand and throw
off the hammer, if the blow (the solar mass) is not strong enough to compress it into a black hole.
-The Iron atoms are compressed to the point that the electrons are collapsing into the protons and fusing them
into neutrons.
-Neutrons are inherently unstable when not combined within a nucleus, and only have a life span of ~13 minutes
before becoming a proton.
-As fusion was occurring in the pre supernova stars, in many different shell layers, many elements in addition to
the large number of central neutrons are dispersed at the time of the super nova explosion.
-These neutrons are captured by the different nuclei released by the dying star, and will quickly decay in to
protons. Thus increasing the atomic number of each atomic nucleus until they progress into the 92 naturally
occurring elements we have discovered.
-The larger the concentration of Hydrogen in a star, the greater the mass, the further the fusion process continues,
the greater combination of elements created upon its super nova death. Unless you’re a star at 20 times the mass
of our sun, and then even crazier results occur upon its death. Or in a brighter light, its rebirth.
Phase 1: Explain Goals and Establish Set
Phase 2: Present Advanced Organizer
Phase 3: Present Learning Materials
* Clarity
* Explaining links and examples
* Enthusiasm
Phase 4: Extending and Strengthening Thinking
* Questioning
* Constructing Discussions
POST INSTRUCTIONAL TASKS
 POST-ASSESSMENT: Fill out graphic organizer to assimilate the understanding of the
progression of nuclear fusion throughout a stars lifecycle, and answer questions related to the
primary concepts of stellar elemental creation.

POSITIVE IMPACT ON STUDENT LEARNING EVIDENCE: Students will answer three
questions for reflection. 1: Why was Hydrogen the primary element created during the big
bang? 2: Why does nuclear fusion within a star end with Iron? 3: Describe in your own words
how every physical object we encounter is created from the stuff of stars.