Physics (Combined Science) · GCSE · OCR · OCR GCSE Combined Science A (Gateway Science) — Physics — Foundation (J250) · Specification point · P4.3 · Waves and radioactivity
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P4.3 Radioactivity
Summary Having considered the general characteristics of waves and particles, we now move on to look at radioactive decay which combines these two ideas. The idea of isotopes is introduced, leading into looking at the different types of emissions from atoms. Underlying knowledge and understanding Learners should have prior understanding of the atomic model, chemical symbols and formulae. An understanding of radioactivity is not expected and should be taught as new content.
Common misconceptions Learners tend to struggle with the concept that radioactivity is a random and unpredictable process. The idea of half-life is another area that can lead to confusion. Learners often find it difficult to understand that irradiating objects does not cause them to become radioactive.
| Learning outcomes | To include | Maths | Working scientifically | Practical suggestions |
|---|---|---|---|---|
P4.3a recall that atomic nuclei are composed of both protons and neutrons, that the nucleus of each element has a characteristic positive charge | M5b |
P4.3b recall that atoms of the same elements can differ in nuclear mass by having different numbers of neutrons |
P4.3c use the conventional representation for nuclei to relate the differences between isotopes | identities, charges and masses |
P4.3d recall that some nuclei are unstable and may emit alpha particles, beta particles, or neutrons, and electromagnetic radiation as gamma rays | WS1.1a, WS1.1b, WS1.2a, WS1.2d, WS1.3b, WS1.3f | Use of a Geiger-Müller tube and radioactive sources to investigate activity. |
P4.3e relate the emission of alpha particles, beta particles, gamma radiation and neutrons to possible changes in the mass or the charge of the nucleus, or both |
P4.3f use names and symbols of common nuclei and particles to write balanced equations that represent radioactive decay |
P4.3g balance equations representing the emission of alpha, beta or gamma radiations in terms of the masses, and charges of the atoms involved | M1b, M1c, M3c |
P4.3h recall that in each atom its electrons are arranged at different distances from the nucleus, that such arrangements may change with absorption or emission of electromagnetic radiation and that atoms can become ions by loss of outer electrons | knowledge that inner electrons can be ‘excited’ when they absorb energy from radiation and rise to a higher energy level. When this energy is lost by the electron it is emitted as radiation. When outer electrons are lost this is called ionisation |
P4.3i recall that changes in atoms and nuclei can also generate and absorb radiations over a wide frequency range | an understanding that these types of radiation may be from any part of the electromagnetic spectrum which includes gamma rays | WS1.1b, WS1.3e | Demonstration of fluorescence with a black light lamp and tonic water. |
P4.3j explain the concept of half-life and how this is related to the random nature of radioactive decay | M1c, M3d, M4a, M4c | WS1.1b, WS1.3a, WS1.3b, WS1.3c, WS1.3e, WS1.3f, WS1.3h, WS2a | Using dice to model random decay and half-life. Research how half-life can be used in radioactive dating. |
P4.3l recall the differences in the penetration properties of alpha particles, beta particles and gamma rays | WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.3a, WS1.3f, WS1.3g, WS1.3h | Use of Geiger-Müller tube, sources and aluminium plates of varying thicknesses to investigate change in count rate. |
P4.3m recall the differences between contamination and irradiation effects and compare the hazards associated with these two | WS1.1a, WS1.1b, WS1.2a, WS1.2d, WS1.3b, WS1.3f | Use of spark chamber to demonstrate a different type of activity counter. |