Understanding Radioactive Decay Through Half-Life Simulations
School
Federal Way Senior High School**We aren't endorsed by this school
Course
CHEMISTRY 101
Subject
Chemistry
Date
Dec 12, 2024
Pages
6
Uploaded by ElderResolve7435
Name:Jasmine NguyenDate:9/24/24Student Exploration: Half-lifeDirections: Follow the instructions to go through the simulation. Respond to the questions andprompts in the orange boxes.Vocabulary:daughter atom, decay, Geiger counter, half-life, isotope, neutron, radiation, radioactive,radiometric datingPrior Knowledge Questions(Do these BEFORE using the Gizmo.)1.Have you ever made microwave popcorn? If so,what do you hear while the popcorn is in themicrowave?The popcorn popping2.If you turn the microwave on for two minutes, isthe rate of popping always the same, or does itchange? Explain.It changes, it usually will increase suddenly andthen slow downGizmo Warm-upLike an unpopped kernel in the microwave, aradioactiveatom canchange at any time. Radioactive atoms change by emittingradiationin the form of tiny particles and/or energy. This process, calleddecay,causes the radioactive atom to change into a stabledaughter atom.TheHalf-lifeGizmo allows you to observe and measure the decay ofa radioactive substance. Be sure the sound is turned on and clickPlay().1.What do you see and hear?Popping of atomsNote: The clicking sound you hear comes from aGeiger counter, an instrument that detects theparticles and energy emitted by decaying radioactive atoms.2.What remains at the end of the decay process?daughter atom3.Is the rate of decay fastest at the beginning,middle, or end of the process?BeginningReproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
Activity A:Decay curvesGet the Gizmo ready:●ClickReset(). Be sure thatUser chooseshalf-lifeandRandom decayare selected.●Check that theHalf-lifeis 20 seconds and theNumber of atomsis 128.Question: How do we measure the rate of radioactive decay?1.Observe: Select the BAR CHART on the right side of the Gizmo and clickPlay.1.What happens to the numbers of radioactive anddaughter atoms as the simulation proceeds?radioactive atoms all die and only thedaughter atoms are left2.Do the numbers of radioactive and daughter atomschange at the same rate throughout the simulation?Explain.They slow down at the end2.Experiment: ClickReset, and select the GRAPH tab. Run a simulation with theHalf-lifeset to 5seconds and another simulation with theHalf-lifeset to 35 seconds.Sketch each resulting decaycurve graph in the spaces below.3.Interpret: How does theHalf-lifesetting affect how quickly the simulated substance decays?The more smaller they are the faster they pop4.Collect data: ClickReset. Change theHalf-lifeto 10 seconds and clickPlay. Select the TABLE tab andrecord the number of radioactive atoms at each given time below.0 s:12810 s:5620 s:3230 s:1540 s:750 s:5Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
5.Analyze: What pattern, if any, do you see in your data?Every 10 seconds the number of radioactive atoms gets reduced to half6.Revise and repeat: Use your data from #4 above to fill in the first line of the data table below. Thenrepeat the experiment four more times. Calculate the average number of radioactive atoms for eachtime.Trial0 s10 s20 s30 s40 s50 s11286028117421285624161353128582512434128734018935128523019134Averages:12859.829.415.29.23.87.Analyze: Ahalf-lifeis defined as the amount of time it takes for half of the radioactive particles to decay.For the simulated substance, every 10 seconds represents one half-life.How does your data demonstrate the definition of a half-life?Every 10 seconds data divides in half8.Revise and repeat: ClickReset. Real radioactive samples will contain billions of radioactive atoms. Tomodel the decay of a large sample, change fromRandom decaytoTheoretical decayon theSIMULATION pane. ClickPlayand record the numbers of radioactive atoms:0 s:12810 s:6420 s:3230 s:1640 s:850 s:4How does this data demonstrate the meaning of half-life?every 10 seconds its divide in halfReproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
Activity B:Measuringhalf-lifeGet the Gizmo ready:●ClickReset.●SelectIsotope Afrom the left drop-down menu.●Check thatTheoretical decayis selected.Introduction:Differentisotopesof the same element have the same number of protons but differentnumbers ofneutronsin the nucleus. Some isotopes are radioactive.Question: How do we find the half-life of a radioactive isotope?1.Observe: Select the GRAPH tab, and clickPlay. Based on the graph, what is your estimate of thehalf-life of isotope A?36 second2.Measure: Turn on theHalf-life probe. Use the probe to measure how long it takes for exactly one-halfof the original radioactive atoms to decay.What is the exact half-life of isotope A?343.Collect data: In the first row of the table below, write how many seconds represent one half-life, twohalf-lives, and so forth. On the next row, predict the number of radioactive atoms that will be present ateach time. Then use the probe to find the actual values.Half-life012345Time (seconds)33369411Predicted #radioactive atoms50402311112Actual #radioactive atoms12860305544.Calculate: Calculate the percentage of radioactive atoms that are left after each half-life.Half-life012345Percentageradioactive atoms4338302216125.Apply: Suppose you found a material in which 12.5% of the original radioactive atoms were present. Ifthe half-life is 47 years, how old is the material?5 years oldReproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
6.Apply: Use the Gizmo to find the half-life ofIsotope B. What is it?857.Practice: ClickReset. Select theMystery half-lifefrom the left menu. In this setting, the half-life will bedifferent each time you run the simulation. Run at least three trials. In each trial, measure the half-lifeusing theHalf-life probeon the graph.When you have found the half-life, click the camera () icon. Right-click the image, and click Copy.Then paste the image below, and label each image with the half-life.8.Explore: Use the Gizmo to explore whether the number of atoms present affects the half-life that youmeasure. Describe your findings below:The less atoms the less time that it takes9.Extend your thinking: The slow decay of radioactive materials can be used to find the age of rocks,fossils, and archaeological artifacts. In a process calledradiometric dating, scientists measure theproportions of radioactive atoms and daughter atoms in an object to determine its age. Carbon-14 is auseful isotope because it is found in wood, ash, bone, and any other organic materials.Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
You can use theHalf-lifeGizmo to model the decay of Carbon-14, which has a half-life of approximately6,000 years (actual value is 5,730 years). In the Gizmo, selectUser chooses half-lifeandTheoreticaldecay. Set theHalf-lifeto 6 seconds (to represent 6,000 years) and theNumber of atomsto 100.Use the Gizmo to estimate the age of each of the objects below. For these questions, each second inthe Gizmo represents 1,000 years.DescriptionAge (years)Egyptian papyrus with 63% of its original carbon-14 atoms4000Aboriginal charcoal with 22% of its original carbon-14 atoms.1800Mayan headdress with 79% of its original carbon-14 atoms400Neanderthal skull with 3% of its original carbon-14 atoms6300Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved