Joseph von Fraunhofer discovered that a. passing light through a prism would create a rainbow b. light could behave as a particle c. there were dark lines in the colour spectrum made by the Sun
Absorption lines happen when a. a cool gas absorbs photons b. a hot gas releases photons c. photons pass through empty space
Scientists can study absorption lines to find out a. the masses of stars b. the distances between stars c. the chemicals present in stars
Discussion/essay questions
Do you know any interesting facts about light? What optical illusions or “tricks of the light” have you seen?
Transcript
In 1814, a German physicist named Joseph von Fraunhofer passed light from the Sun through a prism to create a colour spectrum. He noticed that there were dark lines blocking out certain colours in the spectrum. Today, scientists call these lines absorption lines. Absorption lines happen when particles of light, called photons, move through a cool gas. The atoms and molecules in the gas absorb some of the photons and block certain colours of light. When an atom absorbs a photon, it shows up as a dark line in the colour spectrum. The photons that get absorbed are not random. Every element absorbs specific wavelengths of light, which means every element also has a unique pattern of absorption lines. Scientists can study these lines to find out which chemicals are present in stars and planets.
The most abundant elements in the universe are a. hydrogen and helium b. hydrogen and carbon c. helium and oxygen
During its life, a star can’t use nuclear fusion to create a. helium b. iron c. gold
Heavy elements can be made in a collision between two a. planets b. comets c. neutron stars
Discussion/essay questions
Scientists are beginning to experiment with nuclear fusion as a possible power source. Current nuclear power plants use a process called nuclear fission, which does not produce as much energy. What do you think about nuclear power? Do you think it will help or harm the environment? Why?
Transcript
The simplest chemical elements in the universe, hydrogen and helium, originally formed during the Big Bang. These are the most abundant elements out there. The cores of stars can make more helium through a process called nuclear fusion, where enough energy forces the centres of atoms together to make more complex atoms. Other light elements, like oxygen and carbon, also originate from this process. Iron is the heaviest element that a star can fuse. This usually happens near the very end of the star’s life. There are two ways that heavier elements are made. The first is when stars, especially massive stars, collapse and die. The second is in a collision between two extremely dense star remnants, called neutron stars. These events create enough energy to fuse elements like lead and gold.
An early model of the periodic table sorted elements by a. atomic number b. atomic weight c. number of subatomic particles
The first subatomic particle to be discovered was a. the electron b. the proton c. the neutron
A proton has a. a positive charge b. a negative charge c. no charge
Discussion/essay questions
Even though scientists did not yet understand subatomic particles, the early model that put elements in order of atomic weight still naturally grouped similar atoms together. Why do you think this is? Do you know any other historical examples of humans finding patterns that they didn’t understand?
Transcript
The periodic table is a system that scientists use to organize and classify chemical elements. Originally, many scientists tried to sort the elements by properties. One of the early models of the periodic table arranged elements by atomic weight, which naturally grouped elements with similar properties together. However, certain elements were outliers, and did not fit in their groups. In 1898, a scientist named J.J. Thomson discovered the electron, a subatomic particle with a negative charge. Later, in 1911, a scientist named Ernest Rutherford learned that electrons orbit a nucleus, which makes up most of the atom’s mass. Inside the nucleus, there are protons, which have a positive charge. An atom has an equal number of electrons and protons. This number became known as an element’s atomic number. Today, elements on the periodic table are arranged by atomic number, which gives a more accurate understanding of element properties.
Nuclear fusion is a type of reaction that turns one chemical element into another. The Sun and other use nuclear fusion as a form of power. In high enough , the nucleus of an atom can be separated from its electrons. The heat causes the nucleus to move very quickly. When two nuclei come close enough to each other, they fuse, forming a larger nucleus. This method allows stars to convert hydrogen atoms into helium atoms, and even more atoms after that. Nuclear fusion is a difficult to replicate on Earth, because it requires a lot of heat and pressure. However, many research groups around the world hope to find a way to use it as an source.
Comprehension questions
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Discussion/essay questions
Scientists are interested in nuclear fusion because it would be a clean and powerful energy source. Unlike the type of nuclear power we use today, nuclear fusion would not create dangerous waste. Can you think of any potential disadvantages to this type of energy?
Transcript
Nuclear fusion is a type of reaction that turns one chemical element into another. The Sun and other stars use nuclear fusion as a form of power. In high enough temperatures, the nucleus of an atom can be separated from its electrons. The heat causes the nucleus to move very quickly. When two nuclei come close enough to each other, they fuse, forming a larger nucleus. This method allows stars to convert hydrogen atoms into helium atoms, and even more complex atoms after that. Nuclear fusion is a difficult process to replicate on Earth, because it requires a lot of heat and pressure. However, many research groups around the world hope to find a way to use it as an energy source.