AS 91172 Annotated exemplars

This annotated exemplar is intended for teacher use only. Annotated exemplars are extracts of student evidence, with commentary, that explain key parts of a standard. These help teachers make assessment judgements at the grade boundaries.

Download all exemplars and commentary [PDF, 300 KB]

TKI Physics assessment resources (external link)

For Excellence, the student needs to demonstrate comprehensive understanding of atomic and nuclear physics. 

This involves writing statements that demonstrate understanding of connections between concepts. 

The student has explained the concept of half-life and demonstrated understanding of how it is connected to the quantity of radioactive substance remaining after a period of time (1).

The student has also attempted to link the creation of a new substance by radioactive decay to the concept of atomic number (2).

An explanation is provided for ionisation ability (3).

The student has attempted to explain how the energy that is created in a nuclear reaction is linked to mass / energy equivalence (4).

For a more secure Excellence, the student could further demonstrate comprehensive understanding by:

• giving a more detailed explanation for how radioactive decay produces a new substance, for example by giving an equation for each type of decay to illustrate the concept of conservation of charge and mass number
• giving a more accurate explanation of mass/energy equivalence by showing understanding that energy is measured as mass, not changed from mass.

For Merit, the student needs to demonstrate in-depth understanding of atomic and nuclear physics. 

This involves writing statements that give reasons why phenomena, concepts or principles relate to a described situation.

The student has given reasons for why Thompson developed his model of the atom (1).

The student has also given reasons for how the results of the Gold Foil experiment led to the Rutherford’s development of the structure of the nucleus of an atom (2).

Reasons are also given for why alpha particles have a low penetration ability and has attempted to explain the difference between the penetration power of alpha and beta particles (3).

To reach Excellence, the student could demonstrate comprehensive understanding with statements that show connections between concepts, such as:

• explaining how Thomson’s experiment led to the discovery of the electron
• explaining how the results of the Gold Foil experiment indicated which type of charge the nucleus has, and explaining the presence and distribution of the electrons in the atom.

comparing the sizes of alpha and beta particles to give a more comprehensive explanation for the difference in their penetration ability, and explaining why gamma rays have the least penetration ability.

For Merit, the student needs to demonstrate in-depth understanding of atomic and nuclear physics. 

This involves writing statements that give reasons why phenomena, concepts or principles relate to a described situation.

The student has attempted to give reasons why the Gold Foil experiment disproved Thomson’s model (1).

An attempt to explain how Rutherford was able to use the results of the Gold Foil experiment to predict the structure of the atom was also provided (2).

The student explained how carbon dating relates to radioactive decay (3).

For a more secure Merit, the student could further demonstrate depth of understanding by explaining Thomson’s experiment more fully:

• including the role of the electron in the determination of the structure of the atom
• giving reasons for why only a few of the alpha particles were scattered
• giving reasons for why the density of the nucleus is important in its ability to deflect the alpha particle
• explaining that the rate of decay of C-14 is the same for all living things, so the graph always starts at the same place. 

For Achieved, the student needs to demonstrate understanding of atomic and nuclear physics. 

This involves writing statements that show an awareness of how simple facets of phenomena, concepts or principles relate to a described situation.

The student has described how a fission reaction can create the required heat energy (1).

A description is given that shows an awareness of the principles of fission and fusion (2).

The student has also described the function of alpha particles in smoke detectors (3).

To reach Merit, the student could demonstrate in-depth understanding by giving reasons for the phenomena, concepts or principles, such as:

• using the uranium fission equation to give reasons why mass deficit results in energy release
• explaining how the production of 3 neutrons per fission could result in a controlled chain reaction
• giving reasons why so much energy is needed to bring about a fusion reaction, and explaining the statement that the reactions are governed by the law of conservation of charge and mass
• explaining how alpha particles ionise the air, and how the ionised particles are then able to allow a current to flow.

For Achieved, the student needs to demonstrate understanding of atomic and nuclear physics. 

This involves writing statements that show an awareness of how simple facets of phenomena, concepts or principles relate to a described situation.

This student has shown awareness of how the model of the atom was derived from Rutherford’s Gold Foil experiment (1).

The student has described radioactive decay (2).

The student has described some of the products of nuclear reactions and has given a statement relating to their properties (3)

For a more secure Achieved, the student could demonstrate further understanding by:

• describing how the results of Rutherford’s gold foil experiment led to the proposal that the atom contained a small nucleus
• giving an example decay equation in the description of radioactive decay
• describing that other elements (both radioactive and non-radioactive) are also products of nuclear reactions
• describing what ionisation is, in order to show a greater awareness of the properties of radioactive particles.

For Achieved, the student needs to demonstrate understanding of atomic and nuclear physics. 

This involves writing statements that show an awareness of how simple facets of phenomena, concepts or principles relate to a described situation.

The student has attempted to describe nuclear fission (1).

The student has also attempted to state why Rutherford’s Gold Foil experiment led to the discovery of the nucleus (2).

The student has stated what alpha and beta particles are and has attempted to describe why they have different penetration abilities (3).

To reach Achieved, the student could demonstrate understanding by:

• describing the concept of conservation of mass
• describing the role of other particles such as neutrons
• describing the evidence from Rutherford’s Gold Foil experiment that showed that the majority of the mass of an atom is in what came to be called the nucleus.