Ernest Rutherford Experiments

Exemplar for internal assessment resource 2.5B Physics for Achievement Standard 91172

Exemplar for Internal Assessment Resource Physics Level 2

Resource title: Atomic FAQ
This exemplar supports assessment against:

Achievement Standard 91172

Demonstrate understanding of atomic and nuclear physics
Student and grade boundary specific exemplar The material has been gathered from student material specific to an A or B assessment resource.

Date version published by Ministry of Education

December 2011 To support internal assessment from 2012

© Crown 2011

Exemplar for internal assessment resource 2.5B Physics for Achievement Standard 91172

Grade Boundary: Low Excellence 1. At the excellence level the students are required to demonstrate comprehensive understanding of atomic and nuclear physics. Demonstrate comprehensive understanding involves writing statements that demonstrate understanding of connections between concepts. Written statements must include mathematical solutions and descriptions. Descriptions may include graphs or diagrams. All four aspects have been attempted and comprehensive information has been provided. In relation to the Model of the atom aspect:  The descriptions relating to the Thomson model given in the responses to the first three questions and responses show a comprehensive understanding.  The material presented in questions four and five on the Rutherford model is accurate but not comprehensive in its coverage of the key findings. In relation to the Nuclear Reaction aspect, the material presented is comprehensive and highly engaging in relation to showing how nuclear reactions impact on our world in questions 6,7, 8 and 12. In relation to the Properties of the products of Nuclear Reactions, the work for this section shows a comprehensive understanding of the topic in questions 9, 10, 11. In relation to Power Generation, some high level material has been presented in questions 13, 14, 15 but there is no mention of

Links: to Einstein’s relationship. © Crown 2011 Student 6 page 1: High Not Achieved What was wrong with previous models? J J Thomson invented the plum pudding diagram. The plum pudding diagram was an idea that in the atom the electrons were arranged in non-random rotating rings and all space which was not an electron was a sea of positive charge. We now know that the positive charges within the atom are caused by protons which sit inside the nucleus. How did Rutherford discover the nucleus? Rutherford conducted the gold foil experiment. To do this he fired alpha particles at a thin sheet of gold foil.He proved that the majority of the mass of an atom was in a small portion, meaning that there must be a nucleus holding the protons and neutrons. Why is the gold foil experiment so significant? The significance of the gold foil experiment is that it proved Thomson’s theory of a plum pudding wrong as there isn’t a large amount of mass in the nucleus. What is fission? Fission is a nuclear reaction in which the nucleus splits into smaller parts. This can produce free neutrons and photons, and it releases a large amount of energy. Because of the large amounts of energy it can be used to make bombs, such as the ones dropped on Japan. What is fusion? Fusion is a nuclear reaction which is the opposite to fission as it involves two or more nuclei fusing to become a single heavier nucleus. This process can cause large absorption or release of energy. What is half life? Can it be reversed? Half life is the time it takes for half of a nuclear substance to decay. The rate of decay remains constant throughout the lifetime of the particle. It is not possible to reverse half life but through a fusion reaction it may be returned to a previous state. The properties of products of nuclear reactions Why did Rutherford need alpha particles for his gold foil experiment to work? Alpha particles have the worst penetration ability out of the three nuclear particles. Alpha particles can even be stopped after traveling through a few centimeters of air. Rutherford used alpha particles so that if they hit the nucleus they would be unable to pass and bounce off. Other particles would go straight through the nucleus because of a high penetration ability. Why can beta particles pass through paper while alpha can’t? Beta particles have a very low mass compared to alpha particles and beta particles have a much higher speed. Beta particles are purely electrons and alpha particles are helium nucleus. Because of these differences beta particles can move through paper while alpha particles can’t. Why are gamma rays so dangerous? Gamma rays have the highest penetration ability of the three types of particles. The other two particles can cause cancers or radiation burns on the skin. Because of the gamma rays high penetration it can cause damage throughout the body and is a higher cancer risk. Student 6 page 2: High Not Achieved What are nuclear fuel elements? Nuclear fuel elements are made of uranium oxide, which is a naturally found form of uranium. It is enriched with uranium .235. Nuclear fuel elements can be used to produce large amounts of energy. Where does heat energy from radioactive decay come from? Heat decay is formed when radiation reacts with a material. The energy of either alpha, beta or gamma radiation is converted into heat energy. An example of this occurring in nature is in the core of the earth, when this is constantly occurring. How do nuclear bombs work? Nuclear bombs work because of a chain reaction. Uranium atoms release neutrons, and these neutrons hit another uranium atom, which then releases more neutrons producing a chain reaction and large amounts of energy. What is an alpha particle? An alpha particle is made of two protons and two neutrons bound together in a similar way to a helium nucleus. The alpha particle has the worst penetration ability but has the best ionising ability. What is a beta particle? A beta particle is a free moving electron which is not bound to a nucleus. Beta particles have medium penetration ability and medium ionising ability. What is a gamma ray? It is a wave on the electromagnetic spectrum. It has a short wavelength and a very high frequency. It has a high penetration ability.