Grade 10 Chemistry Review — Radioactivity (Chapter 7 Practice Test)
You've got the Chapter 7 practice test open in front of you — the radioactivity test, twenty-seven multiple choice questions and nothing else.
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Grade 10 Chemistry Review — Radioactivity (Chapter 7 Practice Test)
Two hosts work straight through the Chapter 7 practice test — the radioactivity test — all twenty-seven multiple choice questions, one at a time, with the rule behind each answer and a hook to keep it. The questions and the answers come from the practice test on Mr Schmitt's Science 10 site, whose file carries the answer key beside the questions 1.
What this episode covers
- Questions 1 to 5 — radiation, isotopes, and counting particles. Gamma rays beat microwaves on all three counts at once: shorter wavelength, higher frequency, more energy. Potassium-41 and potassium-39 differ only in their neutrons, so potassium-41 carries two more. For uranium-235 and uranium-238 the ninety-two underneath is the atomic number, which leaves 143 neutrons and 146. Isotopes of one element share their protons, their electrons, and their atomic number, and only their mass number moves. The three formulas that tie the numbers together are the mass number as protons plus neutrons, the atomic number as mass number minus neutrons, and the neutrons as mass number minus atomic number.
- Questions 6 to 9 — telling alpha, beta, and gamma apart. An alpha particle is a helium nucleus: two protons, two neutrons, no electrons around it. Alpha emission takes four off the mass number and two off the atomic number. A beta particle is an electron released when a neutron turns into a proton, so the mass number holds and the atomic number climbs one — and beta is the only one of the three that raises the atomic number. The page's fourth option, lambda, is not a decay at all.
- Questions 10 to 12 — daughter and parent nuclei. Radon-222 alpha decays into polonium-218. Polonium-218, alpha first and then beta, ends as bismuth-214. Run alpha decay backwards from iridium-192 and the parent is gold, at 196.
- Questions 13 to 16 — penetration, half-life, and dating. The diagram with an electron leaving the nucleus is beta decay: same mass, higher atomic number. Beta penetrates more than alpha and less than gamma. Plutonium-242 falling from 10.0 g to 1.25 g takes three half-lives, about 1.2 million years. A daughter-to-parent ratio of three to one means two half-lives, which fits uranium-235 decaying into lead-207 inside 1.5 billion years.
- Questions 17 to 19 — iodine-131 at Chernobyl. Iodine-131 decays by beta emission into xenon-131. Thirty-two days is four eight-day half-lives, which leaves one sixteenth of the parent and gives a ratio of fifteen to one — flagged in the episode: the printed key marks B, seven to one, which is three half-lives or twenty-four days, and the course workbook's own half-life table gives one sixteenth parent and fifteen sixteenths daughter after four half-lives 2. Run the halvings backwards from 10 g at forty days and the original release was 320 g.
- Questions 20 to 27 — decay curves, fission, and fusion. On the strontium-90 curve the fifty percent line lands at thirty years, and five of those half-lives turn 100 g into 3.125 g. Fission splits a heavy nucleus and is what power plants run on; fusion joins light ones and is what the Sun and the hydrogen bomb run on. A reactor runs nuclear, thermal, mechanical, electrical. The fusion equation needs a second helium-3 to balance. The obstacle to fusion power is the temperature, and Hiroshima and Nagasaki were uncontrolled fission chain reactions.
Quick answers
| Question | Answer |
|---|---|
| 1. Gamma rays compared with microwaves | B — shorter wavelength, higher frequency, more energy |
| 2. Potassium-41 and potassium-39 | D — two more neutrons |
| 3. Neutrons in uranium-235 and uranium-238 | C — 143 and 146 |
| 4. What isotopes of an element share | B — I, III, and IV |
| 5. Atomic number, mass number, neutron number | C — I, V, and VI |
| 6. Which symbol is an alpha particle | D |
| 7. Alpha emission and the daughter nucleus | D — mass number down four, atomic number down two |
| 8. Beta emission and the daughter nucleus | C — mass number unchanged, atomic number up one |
| 9. Which decay raises the atomic number | B — beta |
| 10. Alpha decay of radon-222 | A — polonium-218 |
| 11. Polonium-218, alpha then beta | B — bismuth-214 |
| 12. Parent of iridium-192 after alpha decay | C — gold |
| 13. The decay shown in the diagram | B — I and IV |
| 14. Penetrating power of a beta particle | D — less than gamma, more than alpha |
| 15. Plutonium-242 from 10.0 g to 1.25 g | B — 1 200 000 years |
| 16. Ratio of three to one after 1.5 billion years | D — uranium-235 into lead-207 |
| 17. Daughter of iodine-131 | D — xenon-131 |
| 18. Ratio 32 days after the release | C — 15 to 1 (printed key says B, 7 to 1) |
| 19. Original mass of iodine-131 | D — 320 g |
| 20. Half-life of strontium-90 off the curve | B — 30 years |
| 21. Strontium-90 left after 150 years | D — 3.12 g |
| 22. Statements about nuclear fission | C — II and III only |
| 23. Energy transformations in a reactor | B — nuclear, thermal, mechanical, electrical |
| 24. Missing particle in the fusion equation | D — helium-3 |
| 25. Most energy in a hydrogen bomb | D — uncontrolled fusion chain reaction |
| 26. Obstacle to fusion reactors | C — the huge temperatures required |
| 27. Hiroshima and Nagasaki | B — uncontrolled fission chain reactions |
That is the whole Chapter 7 practice test. Press play and study along.
References
- 1Chapter 7 Practice Test — Key
mrschmittscience10.weebly.com
- 2Chapter 7 Workbook — Answer Key
mrschmittscience10.weebly.com
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