Honors Chemistry Unit One Exam

Explain the relationship between cosmic events such as the Big-Bang, supernova, neutron star collisions, and chemistry? Know and be able to explain the origin of elements 1-92.

13.8 billion years ago, the universe began with a Big Bang and it created atoms such as hydrogen and helium. Star cores were consequently fueled by the hydrogen created during the initial phases of the universe. When a star runs out of hydrogen, a supernova event occurs in which the star's core collapses and the star dies. During this process, the star forges elements heavier than iron. When a star dies in a supernova event, the protons and electrons essentially melt into each other to form neutrons. When two said neutron stars collide, they give way to elements heavier than platinum and gold. Chemistry is an umbrella term for the scientific discipline of elements and molecules composed of atoms, molecules, and ions. It describes each of the above mentioned terms.

How many elements are found in nature? Is this number consistent with our modern Periodic Table? Why is this?

92 elements are found in nature and 118 elements are found in the Periodic Table This number is not consistent with our modern Periodic Table because modern technology allows scientists and physicists to use hadron colliders and cyclotrons that create the extreme pressure and heat needed to create heavier elements. They are radioactive, unstable elements because they have a weak nuclear force.

In what way do small to medium -size stars die? How quickly does this happen?

A small to medium-size star dies not by exploding. While their core of iron or lighter elements collapses, the rest of the star expands gently, like a cloud. It swells into a huge, growing, glowing ball. Along the way, such stars collide and darken. They become red giants. Many atoms in the outer halo surrounding such a star will just drift away into space. This process takes place over about 10 billion years.

Explain why a star dies when there is a high concentration of Iron (Fe) atoms in its core? What is the consequence of running out of fuel?

A star dies when there is a high concentration of Iron (Fe) atoms in its core because it attempts to fuse the Iron with Silicon. This expels more energy than the star is receiving, as it has run out of Hydrogen. Thus, there is not enough counter-force (gravity) to counteract this pressure/energy increase. The star then explodes, as the consequence is a supernova.

What percentage of our galaxy is made up of elements heavier than helium? Has that number increased or decreased over time?

About 2% of our galaxy is made up of elements heavier than helium. That number has increased over time due to two main factors: The rise in production man-made elements with an atomic number above 92. The continued fusion of hydrogen and helium.

How do bigger stars (10X the size of our sun) die? How quickly does this happen?

Bigger stars die by using up their fuel. As a result, their core collapses. This leaves them extremely dense and hot. Instantly, that forges elements heavier than iron. The energy released by this atomic fusion triggers the star to expand yet again. At once, the star finds itself without enough fuel to sustain fusion. So, the star collapses once again. Its massive density causes it to heat up again—after which it now fuses atoms, creating heavier ones. It steadily builds up heavier elements. The star then self-destructs in one enormous explosion. The force of that supernova explosion forged elements heavier than iron. Some atoms drift gently from a red giant. Others rocket at warp speed from a supernova. Either way, when a star dies, many of its atoms spew into space. Eventually they become recycled by the processes that form new stars and even planets. This process occurs within a few seconds.

How are elements heavier than 100 created? Explain how man creates elements heavier than Uranium, 92.

Elements heavier than 100 are created through extreme pressure and heat with modern scientific technology. The cyclotron and hadron collider accelerate various protons using magnetic fields to guide them in a circular motion. Though difficult, they eventually collide to form elements heavier than uranium (92).

Discuss how elements heavier than gold, Au-79, are forged? How often does this event(s) occur? Provide a possible explanation why these elements are not forged inside a star core.

Elements heavier than gold, Au-79, are forged through neutron star collisions. After a supernova event, the electrons and protons left combine to form neutrons, thus forming neutron stars. When neutron stars collide, about every 10,000 to 100,000 years, elements heavier than platinum and gold can be formed. When two neutron stars merge they produce jets of high energy particles and radiation fired in opposite directions, thus producing the heat and pressure needed for elements to occur. These elements are not forged inside a star core because the nucleosynthesis/stellar fusion in these stars do not obtain the required energy. They solely run out of hydrogen fuel.

How are you related to the Big-Bang? Provide three pieces of evidence to support your answer.

Every ingredient in the human body is made from elements forged by stars, which are made from elements as small as hydrogen and helium, which were created during the Big Bang. Through a process of expansion and explosion hydrogen gas was created which led to the formation of stars, and their death (supernova) led to the creation of life. All atoms in the human body are billions of years old and are recycled through the universe Our cells have similar structure to that of the universe and the Solar System created from the Big Bang: we have "controlling" nuclei in the center of each of our cells, while the galaxies within the universe have stars: for example, the Sun is the "controlling" force in the center of the Solar System.

Explain the "Hubble Law". Provide an example to demonstrate this law.

Hubble's law is a statement of a direct correlation between the distance to a galaxy and its recessional velocity as determined by the red shift. Hubble's law, also known as the Hubble-Lemaître law, is the observation in physical cosmology that galaxies are moving away from the Earth at speeds proportional to their distance. In other words, the farther they are the faster they are moving away from Earth. The velocity of the galaxies has been determined by their redshift, a shift of the light they emit toward the red end of the spectrum. Hubble's law is considered the first observational basis for the expansion of the universe, and today it serves as one of the pieces of evidence most often cited in support of the Big Bang model. An example of this is the Cosmological Redshift. This is a redshift caused by the expansion of space. As a result of the Big Bang, the Universe is expanding, and most of the galaxies within it are moving away from each other. Astronomers have discovered that all distant galaxies are moving farther away from us, and that the farther away they are, the faster they are moving. Another example is the Doppler Effect, but the light transmittance in waves shows a similar phenomenon.

Information about what is happening in the distant cosmos takes months to thousands of millennia to reach astronomers on Earth. What types of problems could that pose for these scientists, who study the Universe?

One type of problem that this could pose for these scientists is powerful and potentially harmful cosmic events may take place in these distant cosmos and take "months to thousands of millennia to reach astronomers on Earth." These hazardous conditions that would harm Earth would potentially not reach our scientists before it is too late. Another type of problem that this could pose for these scientists is the difficulty of research. The technology used by researchers doesn't relay information to scientists for, again, "months to thousands of millennia to reach astronomers on Earth." Researchers would have to conduct research over multiple generations, as their data would not reach them within their own lifetime.

Explain the concept of the cosmic background microwave radiation (CBM). How was it discovered? What is the significance of this discovery?

The cosmic microwave background (CMB) is thought to be leftover radiation from the Big Bang, or the time when the universe began. As the theory goes, when the universe was born it underwent a rapid inflation and expansion. (The universe is still expanding today, and the expansion rate appears different depending on where you look). The Big Bang Theory not only predicts that this should exist, but it should be visible as electromagnetic microwaves. The CMB represents the heat left over from the Big Bang. This represents the earliest form of radiation that can be detected. Had been detected by orbiting detectors. American cosmologist Ralph Apher first predicted the CMB in 1948, when he was doing work with Robert Herman and George Gamow, according to NASA. The team was doing research related to Big Bang nucleosynthesis, or the production of elements in the universe besides the lightest isotope (type) of hydrogen. This type of hydrogen was created very early in the universe's history. But the CMB was first found by accident. In 1965, two researchers with Bell Telephone Laboratories (Arno Penzias and Robert Wilson) were creating a radio receiver, and were puzzled by the noise it was picking up. They soon realized the noise came uniformly from all over the sky. At the same time, a team at Princeton University (led by Robert Dicke) was trying to find the CMB. Dicke's team got wind of the Bell experiment and realized the CMB had been found. Further, the CMB was forged during the Recombination Era - where the universe cooled enough for protons and electrons to "recombine" into hydrogen atoms.

Which element has the fewest protons, and is considered the lightest? Which element is the heaviest?

The element that has the fewest number of protons and is considered the lightest is hydrogen. It has an atomic number of 1 and has 1 proton. The naturally occurring element that is the heaviest and has the most protons is uranium. It has an atomic number of 92 and has 92 protons. The man made element that is the heaviest and has the most protons is Oganesson. It has an atomic number of 118 and has 118 protons.

Describe the elements forged during a supernova event. Why are the formation of heavy elements limited to supernovas and neutron star collisions?

The elements forged during a supernova event are most commonly Elements 27 - 79. The formation of heavy elements is limited to supernovas, and heavier elements to neutron star collisions, because of the extreme heat and pressure fuse subatomic particles of nuclei together. The force created during a supernova event provides the energy needed to provide the energy to forge elements heavier than iron. The shockwaves produced during a supernova event provides the means of dispersing said elements. Elements are typically forged inside star cores, but once their cores become iron, they self-destruct.

What elements are made as a result of cosmic rays? Are these elements abundant throughout the Universe? Why is this?

The elements made as a result of cosmic rays are lithium, beryllium, and boron. These elements are not very abundant throughout the universe. That is contrary to popular belief, though, because they do have very low atomic numbers. Lithium - 6 × 10-7% Beryllium - 1 × 10-7% Boron - 1×10-7% Lithium, beryllium and boron are rare because although they are produced by extremely rare cosmic ray events, they are then destroyed by other reactions in the stars. The elements from carbon to iron are relatively more abundant in the universe because of the ease of making them in supernova nucleosynthesis.

What do you understand by the term "Nuclear fusion"? How does this term relate to the formation of the elements?

The term nuclear fusion refers to the process in which atomic nuclei fuse to give rise to bigger atoms. This process is also called stellar fusion, nucleosynthesis, or stellar power. This term relates the formation of elements because smaller elements fuse together to form successively larger elements until the production of uranium.

Describe the evidence that supports the Big-Bang theory. How old is the Universe? How do we know this?

The universe is 13.9 billion years old. Astronomers estimate the age of the universe in two ways: by looking for the oldest stars by measuring the rate of expansion of the universe and extrapolating back to the Big Bang One piece of evidence that supports the Big Bang is cosmic background microwave radiation (CBM). Another piece of evidence that supports the Big Bang theory is the mixture of elements. As the Universe expanded and cooled down, some of the elements that we see today were created. The Big Bang theory predicts how much of each element should have been made in the early universe, and what we see in very distant galaxies and old stars is just right. You cannot look in new stars, like the Sun, for this evidence, because they contain elements that were created in previous generations of stars. As such, the composition of new stars will be very different from the composition of stars that existed 7 billion years ago, shortly after the Big Bang. A final piece of evidence that supports the Big Bang theory is the cosmological redshift. The redshift of distant galaxies means that the Universe is probably expanding. If we then go back far enough in time, everything must have been squashed together into a tiny dot. The rapid eruption from this tiny dot was the Big Bang.

Explain the origin of Hydrogen and Helium? What can you say about their abundance in the Universe? How could you explain their relative abundance across the Universe?

Within the Lepton Epoch of the Big Bang, conditions were hot and dense. Thus, protons and neutrons were in the ideal conditions to fuse to each other's nuclei to form hydrogen and helium. Hydrogen was the first and helium was the second atom to be created in the Big Bang. In the universe today, the relative abundance of hydrogen is 73%, while the relative abundance of helium is 25%. They collectively make up about 98% of all atoms in the universe.