Free Printable WorksheetScienceGrade 11Science CurriculumNGSS HS-PS1-8; AP Chem nuclear chemistry connections; CCSS HSS-ID.C and HSN-Q.A.1

11.121 Half Life and Radioactive Decay Models Worksheet

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Worksheet Overview & Skills Covered

Core academic competencies and curriculum alignment

This Chemistry Science worksheet provides structured practice on 11.121 Half Life and Radioactive Decay Models. Students are guided through targeted exercises that build foundational understanding, computational accuracy, and critical thinking skills.

Half-Life and Radioactive Decay Models: Use half-life models, decay curves, and exponential reasoning to determine remaining sample, elapsed time, or activity. Aligned to NGSS, CCSS, AP Chemistry/Pre-AP Chemistry, and representative state chemistry framework crosswalks NGSS HS-PS1-8; AP Chem nuclear chemistry connections; CCSS HSS-ID.C and HSN-Q.A.1 - Half-Life and Radioactive Decay Models Chemistry Standards Crosswalk: National: NGSS HS-PS1-8; AP Chem nuclear chemistry connections; CCSS HSS-ID.C and HSN-Q.A.1. State frameworks: TX TEKS 112.43(c)(14); FL SC.912.P.10.12; NY/CA/NJ HS-PS1-8; GA nuclear standards; VA nuclear chemistry standards.

Whether you are an educator preparing classroom handouts, a tutor reinforcing weekly topics, or a parent supporting homeschool learning, this printable resource gives students the deliberate practice required to achieve subject fluency and master state standards.

Grade

Chemistry

Subject

Science

Domain

Science Curriculum

Formats

PDF & DOCX

Sample Practice Problems

Preview the types of problems and questions covered in this worksheet

Below are sample questions representative of the exercises included on this worksheet and related 11.121 Half Life and Radioactive Decay Models skill assessments:

Problem 1Difficulty: Mastery

Use the curve in the image. Why do equal half-life intervals show smaller and smaller drops in grams?

AThe half-life becomes longer every interval.

BThe isotope changes into a stable element after one interval.

CThe graph should be linear, so the curve is incorrect.

DEach interval removes the same fraction of what remains, not the same mass.

Solution & Explanation:Half-life decay is proportional. Each interval removes half of the remaining nuclei, so the number of grams lost decreases as the remaining sample gets smaller.

Problem 2Difficulty: Mastery

Use the threshold graph in the image. A source starts at 500 counts/min and has a half-life of 5 hours. Approximately when will it first fall below 60 counts/min?

A10.0 hours

B20.0 hours

C15.3 hours

D41.7 hours

Solution & Explanation:Solve 500(1/2)^(t/5) = 60. The result is t = 5 log2(500/60), about 15.3 hours; after that time the activity is below 60 counts/min.

Problem 3Difficulty: Mastery

A mineral originally contained 6.40 g of a parent isotope and now contains 0.800 g. If the parent isotope's half-life is 1.25 x 10⁹ years, what is the mineral's age?

A1.25 x 10⁹ years

B3.75 x 10⁹ years

C2.50 x 10⁹ years

D8.00 x 10⁹ years

Solution & Explanation:The ratio 6.40/0.800 is 8, so 3 half-lives have elapsed. Three times 1.25 x 10⁹ years is 3.75 x 10⁹ years.

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Frequently Asked Questions

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QWhat grade level and standards does this worksheet align with?

This worksheet is designed specifically for Chemistry Science students. It aligns with educational standard NGSS HS-PS1-8; AP Chem nuclear chemistry connections; CCSS HSS-ID.C and HSN-Q.A.1 (National: NGSS HS-PS1-8; AP Chem nuclear chemistry connections; CCSS HSS-ID.C and HSN-Q.A.1. State frameworks: TX TEKS 112.43(c)(14); FL SC.912.P.10.12; NY/CA/NJ HS-PS1-8; GA nuclear standards; VA nuclear chemistry standards.).