Can Tylenol Kill You?

Transcription

1 Can Tylenol Kill You? Every year during the period, there were an estimated: 56,000 emergency room visits, 26,000 hospitalizations, and 458 deaths related to acetaminophen associated overdoses From Acetaminophen Overdose and Liver Injury Background and Options for Reducing Injury on the FDA website: Consider the following example of an exponential decay process: Time Event Total Acetaminophen in Body 8:00 AM An adult takes 2 Tylenol each 1000 mg containing 500 mg of acetaminophen. Percentage of Acetaminophen Remaining in Body 11:00 AM The body will metabolize half of the acetaminophen in 1 half-life. This means that approximately 3 hours later 500 of the 1000 mg has been metabolized. 2:00 PM A second half-life will pass over the next 3 hours as the body continues to metabolize the medication. 5:00 PM A third half-life will pass over the next 3 hours and the body will metabolize 125 mg of the remaining 250 mg in the body. 8:00 PM A fourth half-life will pass over the next 3 hours and the body will metabolize 62.5 mg of the remaining 125 mg. 11:00 PM A fifth half-life will pass over the next 3 hours and the body will metabolize mg of the remaining 62.5 mg. 500 mg 250 mg 125 mg 62.5 mg mg 1. In your own words, what does the term half-life mean? 2. According to the example above, what is the half-life of acetaminophen in the body (in hours)? 3. Will all of the acetaminophen ( the whole ) be broken down after 2 half-lives? Explain. Page 1 of 8

2 4. The previous example assumes that another dose is not taken. Complete the table below assuming that an additional dose (2 Tylenol tablets) was taken every 6 hours for a total of 3 doses throughout the day. Time Event Total Acetaminophen in Body 8:00 AM An adult takes 2 Tylenol each 1000 mg containing 500 mg of acetaminophen. 11:00 AM 2:00 PM 5:00 PM 8:00 PM 11:00 PM 5. What happens to the amount of acetaminophen in the body as successive doses are taken? 6. What would happen to the amount of acetaminophen in the body if someone forgot that they had taken an additional dose and accidentally took more medication? 7. How long will it take for there to be 0 mg of acetaminophen remaining in the body? Explain. Page 2 of 8

3 Half-life Simulation Introduction The nucleus of a radioactive isotope is unstable and spontaneously decays (changes), giving off radiation and changing into a different isotope. The rate at which nuclear decay occurs is constant. Half-life describes the interval of time during which half of the original atoms decay. Sometimes atoms will undergo a series of decays in order to become stable. Radioactive decay can release subatomic particles (protons, neutrons, and/or electrons), energy or a combination of subatomic particles and energy. Essential Question How is the half-life of a radioactive isotope used to determine how much of a sample is left after a given period of time? Materials 1 bag of 100 simulated atoms (with 2 distinct sides) 1 cup Procedure Part 1 1. Obtain a set of atoms (100) and a cup from your teacher. 2. Identify one side (color) of the atom to indicate that it has decayed (changed into a more stable isotope) and record that information in the space above the data table. 3. Fill in the column labeled Predicted Atoms Decayed on Table 1. (You may need to read the rest of the procedure before you can make your prediction.) 4. Place the set of atoms into your cup and shake the atoms using your hand to cover the top of the cup. Pour the atoms out onto a flat surface and count the atoms that have decayed and the atoms that remain and add to the data table. 5. Set the atoms that have decayed aside, since they have decayed you are finished with them. Take the remaining atoms and place them in the cup, shake, and pour out onto a flat surface and count the atoms that have decayed and the atoms that remain and add to the data table. 6. Repeat step 5 until all of the atoms have decayed. 7. Construct a graph using your data of the trials as the independent variable and the atoms remaining in each trial as the dependent variable. Page 3 of 8

4 Data- Part 1 Table 1 Original Number of Atoms Side of simulated atom that represents atoms that have decayed Side of simulated atom that represents atoms that have not decayed (are left) Trial Predicted Atoms Decayed Actual Atoms Decayed (Changed into a more stable isotope) Actual Atoms Remaining (Radioactive isotope) Graph 1 Page 4 of 8

5 Part 1 Analysis 1. How many atoms changed or decayed by the end of the experiment? 2. Compared to the original number of atoms you started with, approximately how many were left after each shake? 3. What does this indicate about the rate at which half-life occurs? Is there a pattern or general trend? Does your graph support this answer? Explain your answer. 4. If each shake represented 500 years of time, what would be the half-life of the atom s radioactive element? 5. This experiment is a model for half-life. The problem with models is that they are usually imperfect. What are some problems with this model in demonstrating half-life? (You may need to complete part 2 before answering this question.) 6. Since models are never perfect, are they useful in helping us understand phenomena? Explain your answer. Page 5 of 8

6 Part 2 Carbon-14 is radioactive carbon continually formed from nitrogen in the atmosphere. It has been used to date (determine the age of) plant and animal remains. All living things use carbon-14 in their life processes. After death, however, the carbon-14 gradually reverts to nitrogen and is therefore no longer present as carbon-14. The reason that carbon-14 reverts to nitrogen-14 is because carbon-14 is unstable. Since nitrogen-14 is significantly more stable, carbon-14 will spontaneously decay (change) to become nitrogen-14. The rate at which the conversion from carbon-14 changes into nitrogen-14 is called its half-life, which is approximately 5,730 years. In another 5,730 years, half of the remaining carbon-14 will be converted, and so on. Organic matter younger than 1,000 years has lost too little radioactive carbon for the difference to be measured. Organic matter older than 60,000 years contains too little carbon-14 to be measured. Organic matter between 1,000 to 60,000 years can be dated by the amount of carbon-14 it contains. This information is extremely useful to the geologist, anthropologist and archeologist. 1. Figure 1 contains a rectangle that has been divided in to 32 sections representing 100% of the carbon- 14 originally found in all living matter. 2. Darken one of the vertical lines to divide the rectangle in half to represent the amount of carbon-14 that decays after 5,700 years (5,700 years is being used as the approximate half-life of carbon-14). Shade the portion that has decayed. Continue to divide and shade the remaining portions to show the amount of carbon-14 decayed after 11,400 years, 17,100 years, 22,800 years, and 28,500 years. 3. Complete Table 2, using Figure 1 as necessary. 4. Using Table 2, plot the fraction of carbon-14 remaining in an organic substance using time as the independent variable on Graph 2. Data- Part 2 Figure 1 100% of carbon-14 found in all living matter (32/32) Table 2 Time Fraction Remaining Decimal value 0 32/ ,700 11,400 17,100 22,800 28,500 Page 6 of 8

7 Graph 2 Part 2 Analysis 7. Will all of the carbon-14 in nature eventually disappear? Explain your answer. 8. Precambrian time is older than 600,000,000 years. Can carbon-14 be used in dating organic substances from that era? Explain your answer. 9. Can carbon-14 be used for dating lava flows? Explain your answer. Page 7 of 8

8 10. What fraction of carbon-14 still remains in charcoal (charcoal is made from plant and animal remains) burned in a primitive man's campfire approximately 28,000 years ago? Use Graph 2 to find the answer. Check your answer using Figure If you started with 800 radioactive nuclei, how many would remain "undecayed" after four half-lives? 12. If 150 "undecayed" nuclei remained from a sample of 2,400 nuclei, how many half-lives have passed? 13. If Co-60 gamma sources have a half-life of 5.27 years. If you had a 10 g sample of Co-60, how much would still be present after 21 years? 14. What does the half-life of a radioisotope (radioactive isotope) tell you? 15. Scientists often make initial conclusions when they are investigating phenomena and then revisit those conclusions after further investigation(s). Look back at your answer to question 1 on Can Tylenol Kill You? How can you adjust your answer as a result of further investigation? 16. Carbon-14 undergoes radioactive decay. Do the carbon-14 atoms disappear after they decay? Are there any scientific laws or principles that you can use to justify your answer? 17. What happens to the carbon-14 atoms when they decay? Why does this happen? Page 8 of 8