Chemistry Lab Notebook | Lab 7: Nuclear Chemistry
Printed Name: Signature: Date:
_______________________ ___________________________ _____________________________
___
Name: Date: Experiment #: 7 Title: Nuclear Chemistry
________________ _________________
Purpose: To measure and compare radioactivity levels of common everyday objects using a Geiger counter; to evaluate
the effectiveness of various shielding materials (paper, aluminum, lead) against beta and gamma radiation from a Cs-137
source; and to investigate the relationship between distance and radiation counts, verifying the inverse square law.
Procedure Data / Results / Calculations
Part 1: Radioactivity of Everyday Objects Part 1: Radioactivity Data
1. Establish background radiation: run the *Net Counts = Measured Counts − Background (4.6)
Geiger counter unobstructed for 200 seconds. Object Counts/ Net Notes
Record total counts. Divide by 10 to obtain the 20s Counts*
equivalent counts per 20-second interval Background 4.6 — 200s run ÷
(background rate). (room) 10
Uranium glass 20 15.4 Contains
2. For each object tested, place the item directly uranium
beneath the Geiger counter detector tube. Using Old lantern 223 218.4 ~50 yr old,
a stopwatch, record the total counts registered in mantles radioactive
exactly 20 seconds. Th
New lantern 3 −1.6 Modern;
3. Objects tested (in order): uranium glass mantles near
(Vaseline glass), old camping lantern mantles background
(~50 years old), new lantern mantles, radium- Radium clock 12 7.4 Radium-
painted clock dial, smoke detector, banana, salt dial painted
substitute (KCl), Brazil nuts, uranium nitrate salt, numbers
desk surface (after uranium nitrate removed). Smoke 7 2.4 Contains
detector Am-241
4. For each object, calculate net counts by Banana 9 4.4 K-40 isotope
subtracting the background rate (4.6 counts/20s) Salt substitute 8 3.4 K-40 isotope
from the measured counts. Net counts represent (KCl)
radiation attributable to the object alone. Brazil nuts 7 2.4 Absorb Ra
from soil
Note: Because radioactive decay is random, Uranium nitrate 243 238.4 Highest
counts measured in a 20-second window will reading
vary slightly between trials. Background was Desk (after 2 −2.6 Confirms no
measured over a longer interval (200s) to reduce removal) contaminatio
this randomness. n
Background Calculation:
200-second run: 46 total counts
Counts per 20s = 46 ÷ 10 = 4.6 counts/20s
Key Findings:
Most radioactive: Uranium nitrate (238.4 net) > Old
lantern mantles (218.4 net). Old mantles were dipped in
thorium solution; uranium nitrate contains radioactive U-
238. Both far exceed background.
Near background or below: new lantern mantles (−1.6),
smoke detector (2.4), Brazil nuts (2.4), salt substitute
(3.4), banana (4.4) — all within random variation of
background.
Desk after uranium nitrate removal: 2 counts (below
background) — confirms radioactive particles do not
Page 1 of 4
Printed Name: Signature: Date:
_______________________ ___________________________ _____________________________
___
Name: Date: Experiment #: 7 Title: Nuclear Chemistry
________________ _________________
Purpose: To measure and compare radioactivity levels of common everyday objects using a Geiger counter; to evaluate
the effectiveness of various shielding materials (paper, aluminum, lead) against beta and gamma radiation from a Cs-137
source; and to investigate the relationship between distance and radiation counts, verifying the inverse square law.
Procedure Data / Results / Calculations
Part 1: Radioactivity of Everyday Objects Part 1: Radioactivity Data
1. Establish background radiation: run the *Net Counts = Measured Counts − Background (4.6)
Geiger counter unobstructed for 200 seconds. Object Counts/ Net Notes
Record total counts. Divide by 10 to obtain the 20s Counts*
equivalent counts per 20-second interval Background 4.6 — 200s run ÷
(background rate). (room) 10
Uranium glass 20 15.4 Contains
2. For each object tested, place the item directly uranium
beneath the Geiger counter detector tube. Using Old lantern 223 218.4 ~50 yr old,
a stopwatch, record the total counts registered in mantles radioactive
exactly 20 seconds. Th
New lantern 3 −1.6 Modern;
3. Objects tested (in order): uranium glass mantles near
(Vaseline glass), old camping lantern mantles background
(~50 years old), new lantern mantles, radium- Radium clock 12 7.4 Radium-
painted clock dial, smoke detector, banana, salt dial painted
substitute (KCl), Brazil nuts, uranium nitrate salt, numbers
desk surface (after uranium nitrate removed). Smoke 7 2.4 Contains
detector Am-241
4. For each object, calculate net counts by Banana 9 4.4 K-40 isotope
subtracting the background rate (4.6 counts/20s) Salt substitute 8 3.4 K-40 isotope
from the measured counts. Net counts represent (KCl)
radiation attributable to the object alone. Brazil nuts 7 2.4 Absorb Ra
from soil
Note: Because radioactive decay is random, Uranium nitrate 243 238.4 Highest
counts measured in a 20-second window will reading
vary slightly between trials. Background was Desk (after 2 −2.6 Confirms no
measured over a longer interval (200s) to reduce removal) contaminatio
this randomness. n
Background Calculation:
200-second run: 46 total counts
Counts per 20s = 46 ÷ 10 = 4.6 counts/20s
Key Findings:
Most radioactive: Uranium nitrate (238.4 net) > Old
lantern mantles (218.4 net). Old mantles were dipped in
thorium solution; uranium nitrate contains radioactive U-
238. Both far exceed background.
Near background or below: new lantern mantles (−1.6),
smoke detector (2.4), Brazil nuts (2.4), salt substitute
(3.4), banana (4.4) — all within random variation of
background.
Desk after uranium nitrate removal: 2 counts (below
background) — confirms radioactive particles do not
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