Unit4 text a revealing secrets of nuclear fission

Pre-reading tasks

1. Otto Hahn, Lise Meitner, Fritz Strassman made several key breakthroughs revealing secrets of nuclear fission. Can you give any information about these scientists? If nothing is known to you, what exactly would you like to learn about them? Think of 4-5 questions the answers to which you expect to find in the text below.

2. In your opinion,

• what is nuclear fission?

• what elements can be bombarded by particles to cause nuclear fission?

• what particles are used for bombardment of elements?

• what are the resultant products of nuclear fission?

3. The words of column A are given in the text. Match them with their definitions.

A	B
fission	to increase the strength.
to coin	functions or duties of a censor.
self-sustaining	most notable, chief.
to amplify	to fasten or tie.
to strike	splitting or division, e.g. of the nucleus of certain atoms.
to bind	university teacher, professional scholar.
censorship	extra, additional
to replicate	able to keep up or maintain oneself.
proof	to hit ; give a blow or blows to.
foremost	to invent (esp. a new word).
excess	to copy, to reproduce, to repeat.
academic (noun)	evidence

Reading

Read the text and fulfill the tasks given in Comprehension check.

Revealing secrets of nuclear fission

Enrico Fermi and his colleagues missed a reaction in the uranium which would later be determined to be the first example of nuclear fission. The task, therefore, fell tо scientist Otto Hahn, who was fast closing in on the secrets of fission. Hahn had studied in his native Germany, and in Britain and Canada, where he had worked with Rutherford and made several key breakthroughs, including the discovery of radiothorium and radioactinium. Returning to Germany in 1906, the next year Hahn began a decades-long

Lise Meitner(1878- 1968) was a key figure in the discovery of fission. Born in Austria, Meitner graduated from the University of Vienna with a doctorate in 1906, and moved to Berlin to work with Max Planck and (Otto Hahn at the Kaiser Wilhelm Institute for Chemistry. Closely collaborating with Hahn, Meitner helped make a number of breakthroughs in the study of radioactivity. Fleeing Hitler’s Germany in 1938 because of the Jewish ancestry, Meitner worked in Sweden, and continued to collaborate with Hahn from abroad, between them designing the experiments that proved that it was possible to split the atom to release energy. (Bridgeman Art Library)

Nuclear fission occurs when an atom “splits”. A uranium 235 atom struck by a neutron fissions into two new atoms, free neutrons and binding energy. For a chain reaction (and a nuclear explosion) to occur, the free neutrons must strike other atoms and split them.

collaboration with Austrian scientist Lise Meitner. Working at the University of Berlin, the two jointly investigated radioactive transformation, and the qualities of beta rays. With Hahn’s student and assistant Fritz Strassman, the two followed Fermi’s work closely and inspired by his results, they began their own series of experiments, bombarding uranium with neutrons. Their great breakthrough came in 1938.

That year was a difficult one. Hitler’s rise to power in Germany had already seen the forced removal of Jewish scientists and academics, including Albert Einstein and Leo Szilard, who had fled abroad. Lise Meitner, with Jewish ancestry, also Jell under the Nazi definition of a Jew, but .is an Austrian national had avoided dismissal and worse. The Anschluss of 1938, with Austria becoming part of the Third Reich, changed her position. One step ahead of the Gestapo, and with the help of Hahn and other friends, Meitner slipped across the Dutch border and made her way to neutral Sweden in July.

With Meitner collaborating via correspondence, the team kept up their work. In December, after bombarding uranium with neutrons, Hahn and Strassman found traces of barium and other elements. The “radium-barium-mesothorium-fractionation” experiment, as it came to be known, demonstrated to Hahn that: the bombardment had Split (Hahn used the term “burst”) the nucleus of the uranium nucleus into the atomic nuclei of the various other elements.

Hahn and Strassman reported their results in late December in an article in a weekly scientific publication, and sent the results to Meitner for analysis. Working with her nephew, refugee scientist Robert Frisch, who was then visiting her, Meitner agreed that the results showed that the nuclei had been split into their lighter elements, releasing neutrons and photons. Frisch coined a new phrase, “fission”, to describe the phenomenon. Hahn and Strassman published an article describing the tests, and Meitner and Frisch separately published on the physics to avoid Nazi censorship. In February 1939, Hahn and Strassman published another article, predicted, as Frisch had pointed out in the analysis he and Meitner had undertaken, that additional neutrons existed and had been released in the experiment. Reading that, Frederic Joliot-Curie and his team were able to replicate Hahn and Strassman’s results - an important scientific proof that the results from Berlin were not a one off, or in error.

Word quickly spread throughout the international community. Physicists in Europe and in the United States were quick to grasp the implications of fission - a number of them, like Szilard, had read The World Set Free. Now thanks to Hahn, Strassman, Meitner, and Frisch’s work, the possibility of generating a nuclear chain reaction a self-sustaining and self-sustaining and amplifying release of neutrons - was no longer just science fiction, Siitard, who had secretly patented the concept, knew it. Neils Bohr, looking at the various isotopes of uranium, specifically uranium-235 and ranium-238 (U-235 and U-238), realized how both could be fissioned. Ernest Lawrence’s laboratory partner at the University of California, Berkeley, J. Robert Oppenheimer, came to a similar conclusion, realizing that the rapid release of excess neutrons, if a chain reaction occurred, meant that an atomic bomb could be built. That was also very clear to Albert Einstein. Like many of the refugee scientists who had fled Hitler; Einstein also realized, with chilling certainty, that if the Nazis grasped the potential and followed through on Hahn and Strassman’s breakthrough, the world was at risk. With that foremost in his mind, and urged on by colleagues, Einstein sat down to write a private letter to the President of the United States.

Frankfurt-born Otto Hahn (1879-1968) was a brilliant chemist who joined Berlin's Kaiser Wilhelm institute for Chemistry. Closely collaborating with Austrian physicist Lise Meitner, Hahn eventually hearted the Institute and was its director until Germany's surrender at the end of World War II, when he was taken into custody by the Allies and interrogated along with other German atomic scientists. Hahn, despite his role in discovering the fission of uranium with Meitner and Fritz Statesman, bad not supported atomic weapons development, and was after the war a prominent advocate against nuclear weapons (Bridgeman Art Library)

Comprehension check

1. Match the names of scientists with the information about them. (Sometimes information refers to more than one scientist).

Otto Hahn	coined a new phrase “fission” to describe the phenomenon.
	found traces of barium and other elements.
	worked with his aunt.
Lise Meitner	studied in Germany.
	discovered radiothorium and radioactinium.
	replicated Hahn and Strassman’s results.
Fritz Strsssman	reported their results in an article.
	made a great breakthrough in 1938.
	collaborated with Lise Meitner.
Robert Frisch	was a partner of Ernest Lawrence
	was a student and assistant of Otto hahn.
	worked together with Otto Hahn at the university of Berlin.
The Joliot-Curies	realized that an atomic bomb could be built.
	left Germany and made her way to neutral Sweden.
	carried out experiments bombarding uranium with neutrons.
Robert Oppenheimer	worked with Rutherford.

2. Check whether you remember the dates and places mentioned in the text.

1. Hahn and Meitner’s great breakthrough came in 1938/1940.

2. Hahn worked in Britain and Canada/Austria.

3. Robert Oppenheimer worked at the University of Berlin/California.

4. Lise Meitner was born in Germany/Austria.

5. Otto Hahn began his collaboration with Lise Meitner in 1906/1907.

6. In 1939/1937 Hahn and Strassman wrote another article.

7. Otto Hahn returned to Germany in 1904/1906.

3. Choose the best ending a, b, or c to complete sentences.

1. Otto Hahn

1. and Ernest Rutherford made some great breakthroughs including the discovery of radiothorium and radioactinium.

2. discovered two radioactive elements: radiothorium and radioactinium.

3. and Lise Meitner found out that thorium was radioactive.

2. Otto Hahn and Lise Meitner

1. researched radioactive transformation and the properties of beta rays.

2. investigated properties of alpha and gamma rays.

3. carried out research into the mysteries of the atom.

3. Hahn, Meitner and Strassman

1. performed a number of experiments researching the properties of uranium.

2. closely collaborated with Fermi.

3. started their own investigation bombarding uranium with neutrons.

4. Hitler’s rise to power

1. resulted in Jewish scientists leaving germany.

2. did not make Lise Meitner flee abroad.

3. prevented scientists from continuing their research.

5. Hahn and Strassman

1. did not inform scientific community about the results obtained.

2. reported their results in a number of articles.

3. published a joint article with Lise Meitner.

6. Hahn and Strassman’s results

1. were disproved by Meitner’s experiments.

2. astonished the international community.

3. were similar to those obtained in the experiments of Joliot Curie and his team.

7. The possibility of generating a nuclear chain reaction

1. was realized.

2. was still science fiction.

3. was missed.

8. Hahn and strassman’s breakthrough

1. meant that the world was at risk.

2. could lead to the construction of an atomic bomb.

3. was used by the Nazis.

4. Find answers to the following questions in the text.

1. Who was the first to reveal the secrets of fission?

2. What did Meitner and Hahn research?

3. Did Hahn know about Fermi’s work?

4. Why did Lise Meitner leave Austria? Who helped her?

5. What did Hahn and Strassman find out while experimenting?

6. Why did they call their experiment “radium-barium-mesothorium-fractionation”?

7. What did the results of their experiments show?

8. How did scientific community learn about Hahn and Strasman’s experiments?

9. Why wasn’t a nuclear chain reaction science fiction any longer?

10. Why did Einstein write a letter to the President of the USA?

5. Prove or disprove the statements below. Give arguments in support of your point of view.

1. Hahn was born and studied in Germany but for some time worked in the USA and Canada.

2. Fritz Strassman was Meitner’s student.

3. Unlike Fermi, Hahn and Strassman bombarded uranium with protons.

4. 1938 was a difficult year.

5. Meitner worked together with Hahn and Strassman.

6. Meitner analyzed the results of Hahn and strassman’s experiments.

7. The Joliot-Curies managed to get the same results as Hahn and Strassman by repeating their experiment.

8. Everybody understood that if a chain reaction occurred it would mean that an atomic bomb could be built.

6. Organize the jumbled sentences in the right order.

1. Meitner could no longer work with Hahn and Strassman as she had to leave Germany.

2. Soon the international community learnt that a nuclear chain reaction was no longer science fiction.

3. Otto Hahn was to fulfill the task – to generate a nuclear reaction.

4. Some scientists realized the danger of using Hahn and Strassman’s breakthrough for military purposes.

5. They reported their results in a number of articles.

6. Otto Hahn discovered several radioactive elements.

7. Nevertheless, the team collaborated via correspondence.

8. Meitner and Hahn worked at Berlin University researching radioactive transformation and the properties of beta rays.

9. They conducted a set of experiments bombarding uranium with neutrons.

10. Hahn and Strassman made a number of experiments and found out that the uranium nucleus had split into atomic nuclei of other elements.