CHEM120 Week 6 Concepts: Nuclear Chemistry, Energy, and Biochemistry- Download To Score An A+

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CHEM120 Week 6 Concepts: Nuclear Chemistry, Energy, and Biochemistry- Download To Score An A+ LAWS OF THERMODYNAMICS In this section, we explore the rules of energy that we observe in the universe... . We see many examples of these laws in action on a day-to- day basis. You will learn how to compare and contrast exothermic and endothermic reactions as well as the first and second laws of thermodynamics. 1. Which of these would you classify as an exothermic process? o Evaporation of alcohol o Photosynthesis o Wood burning o Ice melting 2. Which one of these processes would NOT be possible? o Energy is transferred in a chemical reaction o Energy is created in a chemical reaction o Two liquid chemicals are mixed together, and the temperature of the mixture rapidly cools o Energy spontaneously flows from a hot object Energy cannot be created or destroyed in a chemical reaction. ENERGY AND FIRST LAW OF THERMODYNAMICS Energy takes many forms. A few of the more common forms of energy we observe are light, heat, mechanical energy, and electricity. Energy is the driving force of this universe and necessary for all life, light, and movement. Energy can be measured using various units, including calories and joules. This law is often also known as Conservation of Energy, as this law tells us that energy is conserved and simply moved from one place to another and one form to another. For example, when you drive a car down the road, you are converting the chemical energy found in gasoline into heat and kinetic (movement) energy. None of this energy is destroyed or eliminated in this process. As another example of the first law of thermodynamics in action consider a falling stone hitting the earth. The kinetic energy of this stone is converted mainly into sound, and vibration. In both of these examples, we see that energy can move from one form to another. You may have noticed the term “isolated system” in the 1st Law of Thermodynamics. This term means a system where no matter and no energy go into or out of the system. Our universe, as we understand it, is an example of such a system, so this law applies to our universe. SECOND LAW OF THERMODYNAMICS The second law of thermodynamics tells us about how energy in the universe behaves in terms of flow and organization. The amount of entropy in an isolated system irreversibly increases over time. This law tells us that the amount of entropy, or disorder, in the universe is constantly increasing. An important reason for this is that heat spontaneously and irreversibly transfers from a hot body to a cold body. An example that illustrates both of these points is a cup of hot coffee sitting outside on a cold winter's day. At first, the heat is localized into the area of the liquid in the cup; however, the heat quickly begins to disperse into the surrounding environment spontaneously. Over time, the coffee in the cup will have the same temperature as the surrounding environment as the temperatures even out. In this way, we see that: • Heat was spontaneously and irreversibly transferred from a higher temperature system area to the lower temperature surroundings. • Disorder increased as the localized heat spread through the surroundings. 3. For each of the situations, determine if the observed behavior is a consequence of the first or second Law of Thermodynamics: Situation Select Law As a rocket takes off, energy in the fuel is converted into kinetic energy, heat, and light. 1st Law of Thermodynamics An ice cube melts on a hot day. 2nd Law of Thermodynamics On a hot day, you turn on the oven, causing the room to become even hotter. 2nd Law of Thermodynamics Turning on a computer results in electricity being converted into mechanical work, heat, and light. 1st Law of Thermodynamics ENDOTHERMIC AND EXOTHERMIC REACTIONS Energy can flow into a system from the surroundings or from the surroundings into the system. The terminology we use for these processes is: • Exothermic: Energy from system to surroundings (energy released) • Endothermic: Energy from surroundings to system (Energy absorbed) The image illustrates this process. We often measure this energy in the form of heat, so heat flowing from the system to the surroundings is considered exothermic, while heat flowing into the system is considered endothermic. A good mnemonic is that exo = exit (energy exits). An example of an exothermic process is a burning match. The burning match releases heat into the surroundings and is thus classified as exothermic. On the other hand, you may have used a chemical cooling pack to treat an injury. In a chemical cooling pack, the chemical reaction absorbs heat from the surroundings, cooling your injury. Since energy is going from the surroundings to the system, we would consider this process endothermic. What about ice melting? Would you consider this to be endothermic or exothermic? Is energy going in, or is energy going out? Ice melting is endothermic as energy goes into the ice, giving the molecules of water the energy they need to move more quickly. This transforms the solid. As a material absorbs energy (endothermic), the atoms and molecules in the material move more quickly and the state of the material changes from solid to liquid to gas. Opposingly, as a material releases energy (exothermic), the atoms and molecules slow down, moving from gas to liquid to solid. 4. Match the reaction to the type: o Endothermic o Photosynthesis o Chemical ice packs o Methanol evaporating o Iron melting o Exothermic o Water freezing o Burning gasoline o Water condensing on a cool surface o Two chemicals are mixed together, producing heat 5. When a cool penny is placed in a hot car in the summer, the heat flows spontaneously from the interior of the car to the penny in an illustration of the 2nd Law of thermodynamics. 6. Sort the following process as exothermic or endothermic: o Endothermic: o A pair of chemicals are mixed together in a beaker and the beaker becomes cold o Carbon dioxide converts from a solid to a gas o Exothermic: o Your body digests food for energy, generating excess heat o On a humid day water condenses on a cool surface o Wood burns in a bonfire 7. When sodium hydroxide is dissolved in water within a beaker, you observe that the beaker becomes warm. This situation illustrates: o The 2nd Law of Thermodynamics o The 1st Law of Thermodynamics o An Exothermic reaction 8. Select all the following situations that you would classify as endothermic processes: o Ammonium nitrate dissolves in water and the solution becomes cold o Lava cools and becomes a solid o Butane combusts to give a flame in a lighter o Hand sanitizer evaporating RADIATION When we hear the word radiation, often our minds turn to power plants, nuclear weapons, and reactors. In fact, radiation is so much more and has been part of our universe from the very beginning. In this lesson, we will explore the concept of radiation and the types of radiation that we encounter. 9. Which of the following are types of electromagnetic radiation? o X-rays o Alpha particles o Light o Radio waves 10. Which type of radiation would you consider ionizing radiation? o Visible light o Microwaves o Gamma rays o Sound waves 11. Which of the following procedures in healthcare involve the use of radiation to take images? o Temperature measurements using thermometers o Pulse measurements o CT scans o X-Ray Radiation is a broad term that refers to energy transferred over distance as rays, particles, or waves. Radiation has always been a part of our world. By the end of this lesson, you should no longer think of all radiation as dangerous, as there are many forms of radiation with a wide range of properties. The main categories of radiation we will be focusing on are: • Particulate radiation: Energy transmitted through small particles • Electromagnetic radiation: Energy transmitted through waves or rays without mass Particulate radiation includes alpha particles as well as electron-based transmission, known as beta particle radiation. These types of radiation have mass, even if that mass is incredibly small. You will learn more about the properties of particulate radiation at another time. Electromagnetic radiation has no mass and includes X-Rays, all forms of light, radio waves, microwaves, and all other sources of radiation without mass. As you see from the examples, you are always being exposed to electromagnetic radiation any time there is any degree of light in your presence. Electromagnetic radiation can also be said to exist as massless particles of energy known as photons and exist simultaneously as particles and waves. IONIZING AND NON-IONIZING RADIATION Another way to categorize radiation is as ionizing or non-ionizing radiation. As you may recall, ions are charged atoms or molecules. • Ionizing radiation is radiation that is able to cause atoms or molecules to become charged by removing electrons. • Non-ionizing radiation is NOT able to cause the formation of ions as types of radiation that fall into this category and cannot remove electrons from atoms or molecules. The reason that some radiation is ionizing, and others are non-ionizing comes down to energy. High energy radiation is better able to cause ionization than lower energy forms. This is because it takes energy to remove electrons. These categories of radiation overlap with the other categories of radiation: particulate and electromagnetic. As an example, visible light is a type of electromagnetic radiation that is non-ionizing while X-Rays are a type of electromagnetic radiation that is ionizing. RADIATION ALL AROUND US Now that we understand the major classes of radiation, let us look into specific examples in the real world. Radiation appears in many forms, and before moving on, take a moment to identify some forms of radiation that you may be exposed to right now. Once you have recorded the types of radiation you propose you are being exposed to, keep this on hand as we explore real world sources of radiation. Keep in mind, this is not an exhaustive list, but will give us the ability to identify radiation we encounter on a day-to-day basis. LIGHT As previously mentioned, all light is a form of radiation. Light exists as both a particle and a wave and, like all other sources of electromagnetic radiation, consists of photons. The light that we see, known as visible light, is only part of the light that we are exposed to. Light exists as a spectrum of wavelengths with shorter wavelengths being higher in energy. • On the long wavelength end, we have radio waves, cell phone waves, microwaves, and infrared radiation. These are all non-ionizing. • Next, we have visible light, which is the type of light that we are able to see as humans. This radiation is not ionizing. • Higher in energy than visible light, with have ultraviolet (UV light), followed by X-rays and gamma rays. At the high end of the UV scale and beyond, this radiation is ionizing. The spectrum above illustrates the electromagnetic spectra of light. This light is emitted from a variety of sources with examples given below: Source Electromagnetic sources released Sun Entire spectra Incandescent bulbs Visible and partially into infrared White LED Visible Tanning bed bulbs Ultra violet Microwave ovens Microwaves 12. Is the type of radiation ionizing or non-ionizing? o Ionizing: o X-rays o Gamma Rays o Non-ionizing o Microwaves o Infrared o Radio Waves o Visible Light RADIATION IN HEALTHCARE CT scans use X-rays, while PET scans use a type of radiation called positrons which you will be studying in a later lesson. Radiation therapy is a broad term for the use of radiation to treat conditions ranging from cancer to hyperthyroidism. Healthcare workers protect themselves from repeated and long-term exposure to the radiation present in healthcare through the use of personal protective equipment (PPE), shielding (blocking radiation), and distance. For a patient, the risk of short-term radiation therapy or a scan may be minimal, but for a worker in contact with these sources of radiation daily, repeated exposure is a concern. This is why X-ray technicians will go behind a wall or into a booth before turning on an X-ray instrument. OTHER SOURCES OF RADIATION We are exposed to radiation at all times. You are exposed to radiation within your body, in the environment, and even from space. Some of this radiation is ionizing radiation. The good news is that our bodies are constantly on the lookout for radiation damage and can heal from this in most cases. In addition to the sources of radiation we have covered thus far, other sources of radiation we are exposed to on a day to day basis are: Radon gas: Radon is a radioactive gas that is found within the earth’s crust. Radon produces ionizing radiation and is a leading cause of lung cancer. As this gas can easily leak into homes, radon testing, and mitigation can minimize exposure. Out of all of the sources of radiation we have studied, this is one of the most dangerous ones that we can most easily mitigate. Cosmic radiation: These radioactive subatomic particles come from the sun, cosmic events in the galaxy such as supernovas, and even from outside of the galaxy. Most of these passes harmlessly through the earth and our bodies. You are exposed to more cosmic radiation if you fly frequently as higher altitudes are less protected by our atmosphere. Internal radiation: A very small percentage of the isotopes in our bodies (such as potassium-40) are radioactive. This means that each person is slightly radioactive. This radioactive material comes from food and water we ingest. For example, bananas, due to their high potassium content, have slightly elevated levels of potassium-40. You may notice that nuclear power plants are not on this list. This is because, if functioning correctly, a nuclear power plant does not release very much radiation. Radioactive waste, if properly stored, also does not result in a significant contribution to overall exposure. 13. Classify the sources of radiation as ionizing or non-ionizing: o Ionizing o Radon o CT scan o High energy UV lamp o The sun o Non-ionizing o Microwave ovens o Cell phones 14. Select all that would be considered sources of ionizing radiation. o Cell phones o CT scans o Microwave ovens o Radon gas 15. This type of radiation cannot remove electrons from atoms or molecules: o Particulate o Ionizing o Electromagnetic o Non-ionizing 16. Determine if each of the following electromagnetic radiation types is ionizing or non-ionizing: o Ionizing o Gamma rays o Non-ionizing o Infrared o Radio waves 17. Radiation that has mass and can cause atoms and molecules to become charged would be classified as: o Particulate o Non-ionizing o Electromagnetic o Ionizing Understanding the categories of radiation can help us to understand the properties of different types of radiation. Ionizing and particulate are both classifications of radiation that can cause atoms and molecules to become charged. 18. In the field of healthcare, ionizing radiation is used for: o Measuring blood pressure o Measuring heart rate o Temperature measurements o CT scans RADIOACTIVE ISOTOPES You have likely heard the term “radioactive material” in the past. In this lesson, we will learn how radioactive isotopes decay on a subatomic level and what types of radiation they produce. Be sure to have your periodic table on hand for this concept. 19. Which type of radiation would penetrate most deeply into your body? o Alpha o Beta positron o Gamma o Beta electron 20. Which of the subatomic particles below are found in the nucleus of the atom? Select all that apply. o Neutron o Electron o Isotope o Proton 21. Which type of radiation would penetrate most deeply into your body? o Gamma o Beta electron o Beta positron o Alpha 22. The atomic symbol of an element can be determined from the: o Mass number o Atomic mass o Atomic number o Neutron number NUCLIDES A nuclide is an isotope that exists long enough to be measured. You likely remember the term Isotope from earlier in the session and this term refers to atoms of a specific element that differ based on their mass number. A few more important terms to remember: Proton: +1 charged subatomic particle found in the nucleus with a mass of 1 AMU Neutron: uncharged subatomic particle found in the nucleus with a mass of 1 AMU Electron: -1 charged subatomic particle with a very small mass (~0) Mass number (abbreviated as: A): Protons + neutrons Atomic number (abbreviated as Z): Number of protons in an atom. Determines atomic symbol. In the image above, we see the nuclide with the protons p+ and the neutrons n0. As can be seen in the image, an atom with this nucleus would have 4 protons, an atomic number of 4 (number of protons), 5 neutrons, and a mass number of 9 (protons + neutrons). Looking at the periodic table, we would also see that this element must be Beryllium (Be) as this is the element with an atomic number of 4. We can represent this nuclide in isotope form, as outlined OR, we can represent this nuclide in shorthand, where we just show the name or symbol of the element with the mass number after the dash: Beryllium-9 OR Be-9 23. Using the descriptions, match each to the correct isotopes o An isotope with a mass number of 131 and an atomic number of 53 o Iodine-131 o An isotope of phosphorus with a mass number of 32 o Phosphorus-32 o An isotope with a mass number of 53 and 25 protons o Manganese-53 RADIOACTIVE DECAY The reason radioactive material is radioactive is that such material contains unstable isotopes. Remember the term isotope refers to atoms of a specific element that differ based on their mass number. Radioactive decay: The spontaneous process by which an isotope with an unstable nucleus decays by re- releasing matter and/or energy from the nucleus. The three main types of radioactive decay are: • Alpha decay • Beta decay • Gamma decay There are two types of beta decay, electron and positron. All of these are forms of ionizing radiation. The table below shows the types of radiation released from each type of decay as well as the type, mass, and charge. Type of Decay Radiation released Mass of particle Charge of Particle Type of Radiation Alpha 4 α 2+ 2 4 +2 Particulate Beta (electron) 0 β - −1 ~0 -1 Particulate Beta (positron) 0 β + 1 ~0 +1 Particulate Gamma 0γ 0 0 0 Electromagnetic In this table, we see that all of these types of decay release particulate radiation except gamma. This is because each of the radiation types has some mass, with the exception of gamma decay where a massless photon of gamma radiation is released. Important Note: Mass and charge are conserved in all decay processes. In other words, the total mass and charge must be the same on both sides of the reaction. NUCLEAR DECAY PRODUCTS Different types of radiation have different penetrative power. As a general trend, the less massive the type of radioactive particle, the greater the penetration. In order of penetration we have: • Alpha particles- least penetrative ability • Beta particles- intermediate penetrative ability • Gamma particles- greatest penetrative ability What this means to your body is that some of the types of radiation are able to penetrate deeper than others. As illustrated, alpha particles are blocked by your skin, while beta particles can penetrate into your tissues, and gamma particles can penetrate all the way into your bones and organs. The reason for this different penetrative ability is largely due to the speed at which each type of radiation is traveling as well as the mass of the particles. Because of these differences, alpha particles can be blocked by a sheet of paper while gamma rays require a few cm of lead, a great radiation blocking material, to fully block them. Speaking of blocking of radiation, lead is great material for shielding from radiation. Lead is the gold standard for blocking radiation and is used extensively in the containment of radioactive materials. ALPHA DECAY The first type of radioactive decay we will examine is Alpha Decay. In alpha decay, an unstable isotope breaks down by ejecting part of the nucleus, specifically, ejecting an alpha particle. An alpha particle is composed of two protons and two neutrons and is commonly expressed as: 4He 2+ or 4 2+ The reason we can express this as an He2+ is that this particle has an atomic number of 2 (therefore helium) and, as this particle does not have any electrons, the +2 charge from the protons is not balanced out. One unstable isotope that undergoes alpha decay is Tellurium-104. Note in the equation below how the total of the top number and the total of the bottom number does not change due to conservation of mass and charge. 104Te → 4α 2++ 100Sn As we see here, the Te released an alpha particle. In the process, the mass number of the Te isotope decreased by 4 and the atomic number decreased by 2. The atomic number of the new nucleotide decreased by 4 from 104 to 100. Since the atomic number (number of protons) is what determines the atom we have, the resulting nucleotide is now Sn instead of Te. We know this because the nucleotide formally known as Te now has 50 protons and, looking at the element with 50 protons on the periodic table, we see that we now have Sn. This process of converting from one element to another is called transmutation. We see transmutation occur in most types of radioactive decay. Below is a model of an alpha decay. Note how the alpha particle is emitted, leaving behind a new nucleotide. Please note that an alpha particle is always 2 protons and 2 neutrons as seen below. 4 2 Alpha decay is unique in that this is the only type of radioactive decay we are studying that changes the mass number of the resulting nucleotide. This illustration below shows the original particle undergoing alpha decay and emitting an alpha particle (the small particle), leaving a new nucleotide (the circle particle). BETA DECAY: ELECTRON There are two types of beta decay: electron and positron. The key difference between the two is that the electron beta particles have a negative charge while the positron beta particles have a positive charge. We will start by studying the electron version of beta decay. In electron beta decay, a neutron is converted to a proton and emits an electron in the process. Please note that this electron is not one of the electrons outside the nucleus, and instead is emitted directly from the nucleus. As you likely remember from prior lessons, an electron has a -1 charge and a small mass of ~0 and thus the beta particle is expressed as: 0 - 0 - −1 −1 When an electron is emitted from a neutron, the neutron becomes a proton. The reason behind this is similar to the reason that atoms become positively charged when emitting electrons: when negative charge is lost, a system becomes more positive. Therefore, when a neutron emits a negative charge, it gains a positive charge and is thus a proton (neutrons cannot have + charges). This means that in beta decay: a neutron becomes a proton by emitting an electron. An example of electron beta decay appears below as oxygen-19 decays. 19o→ 0 - 19 −1 As we see above, our atomic number (number of protons) increases (from 8 to 9) for the oxygen, transmuting the oxygen into a fluorine nucleotide. This is consistent with our understanding that a neutron becomes a proton during beta decay. We also see again our conservation of both mass and charge as the top number has a total of 19 on both sides while our bottom number has a total of 8 on both sides. Once again, we know that the nucleotide product is F as the periodic table tells us that any atom with an atomic number of 9 is an atom of F. The model below shows the beta decay of Oxygen-19. As we can see, a neutron becomes a proton by releasing an electron. In the process, the atomic number is increased by one while leaving the mass number unchanged. We see that for the atomic number, we have 8-(-1) =9. BETA DECAY: POSITRON In many ways, positron beta decay is the opposite of electron beta decay. In positron beta decay, a proton is converted into a neutron as a positively charged beta particle is released. This beta particle is equal and opposite in charge to an electron and can be expressed as: 0 + 0 + +1 +1 Because the charge of this particle is the opposite of an electron, we also expect the opposite effect. In this case, a proton is releasing a positively charged particle, and in the process, becomes neutral. This is why this reaction converts a proton into a neutron as the positron is released. An example of this process is the decay of Nitrogen-13. 13 0 +1 + +13C We see in the decay process above that the positron released converts a proton into a neutron, decreasing the atomic number of the nucleotide by one. This decrease in atomic number changes the element from nitrogen to carbon as the atomic number changes to 6. The positron emitted always has a + charge and a mass of ~0. Additionally, we see that the mass number is not changed in this reaction and that we have conservation of both mass and charge. We also can note that we can determine the atomic number of the product nuclide, noting that this process will decrease the atomic number by one. Below is a model showing the positron decay of Nitrogen-13. As we expressed in isotope form, we see the conversion of a proton into a neutron. 24. Complete the radioactive decay by dragging the correct products of each decay to the corresponding box. o Alpha decay of Pu-240 236 92 o 2 o Beta (electron) decay of Cd-118 118 49 o −1 o Beta (positron) decay of In-98 98 48 o +1 + GAMMA DECAY Gamma decay, the most penetrating and fast-moving type of radiation we will be studying, is distinct from the other types of decay we have studied. In addition to being massless, the release of gamma radiation does not cause any form of transmutation and will change neither the atomic number nor the mass number. Instead, gamma decay involves a nucleus entering a lower energy state and releasing gamma radiation in the process. A gamma ray is expressed as: 0 0 An important example of an isotope that undergoes gamma decay is an isotope of Technetium: Tc-99m. The m stands for metastable (metastable means that the nucleus is in a relatively high energy state). This isotope is widely used in medical imaging and is vital to the field of healthcare. When the nucleus of Tc- 99m stabilizes, a gamma ray is produced as seen in the reaction below: 99 mTc ⟶ 0γ +99Tc 43 0 43 As we see above, while the nucleotide stabilized, no transmutation occurred as there was a 0 for both the atomic number and charge of the gamma particle. The gamma ray released is a type of high energy photon. Below, we see a model of the nucleus of Tc-99m rearranging into a stable nucleus and releasing a gamma ray in the process. Electron Capture Electron capture is a relatively rare method by which unstable isotopes can become stable. Few isotopes use this method, which involves, like positron emission, a proton becoming a neutron. However, unlike in positron emission where a positron is emitted, in electron capture, as the name suggests, an electron is captured by a proton, resulting in the formation of a neutron. The mechanism for a proton converting into a neutron in electron capture can be explained through charges. As we know, electrons have a -1 charge while protons have a +1 charge. If a proton and electron are combined, we see the +1 and -1 charges cancel to form a charge of 0, the charge of a neutron. Also, unlike the other radioactive processes we saw where an unstable isotope is stabilized by emitting, in electron decay, the electron is absorbed. Consider the electron capture of Beryllium-7: 7Be+ 0 - →7Li As we see above, the electron is on the reactant and NOT the product side. As the electron is absorbed, the atomic number decreases from 4 to 3 as a proton becomes a neutron. The new atomic number of 3 shows us that the product is a nucleotide of Li that can be written as Lithium-7. This reaction is also modeled below: 25. To wrap this up, you will be completing the table below, summarizing each type of radioactive decay studied. Be sure to review the previous sections to brush up on these and then use your understanding of the content to summarize. Type of Process Effect on mass number Effect on atomic number Alpha Decrease by 4 Decrease by 2 Beta electron No change Increase by 1 Beta positron No change Decrease by 1 Gamma No change No change Electron capture No change Decrease by 1 26. If Magnesium-21 undergoes beta positron decay, I would expect the products of this decay to be a positron and a o Alumium-22 o Sodium-20 o Magnesium-20 o Sodium-21 27. A proton absorbs an electron. What effect would you predict this to have in an unstable isotope? o Increase in mass number o Decrease in mass number o Increase in atomic number o Decrease in atomic number 28. During a type of radioactive decay, the atomic number of an isotope increases by one while the mass number is unchanged. I would expect that this is caused by: o a proton combining with an electron o protons and neutrons being ejected from the nucleus o a neutron becoming a proton o a proton becoming a neutron 29. 29. 171 80 171 81 undergoes alpha decay forming an alpha particle and 173 82 167 78 171 79 30. Determine the products of the beta electron decay of Vanadium-52 (select all that apply): 52 23 o −1 - 52 24 31. Select all processes which cause a decrease in the atomic number of an isotope. o Gamma Decay o Beta Positron Decay o Electron Capture o Beta Electron Decay o Alpha decay 32. Sort the following types of radiation in regard to their ability to penetrate the human body from top (most) to least (bottom). o Gamma o Beta Electron o Alpha APPLICATIONS OF RADIATION In this final concept on radioactive isotopes, we will be exploring the concept of half-life as well as the applications and risks of radiation. 33. How many grams of a 4 grams sample of a radioactive material will remain after two half-lives? o 4 grams o 2 grams o 1 gram o 0 grams 34. Which of the following technologies depend on radioactive isotopes to function? Select all that apply. o PET Scans o Microwaves o Nuclear power generation o Light bulbs HALF LIFE In nuclear chemistry, half-life is a measure of how much time is required for the radioactivity of a specific radioactive material to decrease to half the original value. As we explored earlier, unstable isotopes decay over time. Some radioactive isotopes decay more quickly than others, and thus a wide range of half-life values are possible, from infinitesimal fractions of a second to longer than the current age of the universe. Radioactive isotopes decay using one or more of the radioactive decay types you have studied. These processes occur over time and if we know the half-life of a given radioactive material, we can predict how much of that material will still be radioactive after a given period of time. Radioactive Iodine-131, an isotope frequently used in healthcare, has a half life of 8 hours. This results in the radioactivity of Iodine-131 decreasing by half of its current value every 8 hours. As you see, this results in an exponential decrease in the radioactivity of this material over time. Please note the dotted line indicating the trend of this decay. This chart also shows us that after 16 hours, two half-lives have occurred, meaning that this sample only has 25% of the original radioactivity after this period of time. DETERMINING HOW MANY HALF-LIVES HAVE PASSED If the episodes of a show that you would like to watch are each 30 minutes long, how many episodes could you watch in 90 minutes? This was likely a very simple problem to solve by simply considering how many times 30 fits into 90. In other words, you divided the time that you had (90 mins), by the time of an episode (30 mins). This told you how many episodes could fit in that time frame. This is the same way we will use to determine how many half-lives have occurred! How much of a radioactive sample that will remain over time depends on both the half-life of the material as well as how much time has passed. The more time that passes, the less of your original radioactive sample you have. The first step to completing half-life calculations is to determine how much of a material remains after a given period of time. Let us consider a specific situation: If we had a sample of radioactive material with a half-life of 30 minutes, how many half-lives will have occurred in 90 minutes? To solve this, I would simply divide the time that has passed by the half-life, making sure both times had the same unit: total time = 90 min =3 half lives half life 30 min As we see above, just like the question on episodes that you solved earlier in this lesson, we simply divided 90 mins by 30 mins to determine how many times 30 could fit into 90. This told us how many half-lives could fit in the time frame. As another example, let us say that a material has a half-life of 12 hours. How many half-lives have happened in two days? To solve this, we would again divide the total time by the half-life: total time = 48 hours =4 half lives half life 12hours Note how we used 48 hours for the total time instead of 2 days. This is because both units of time must match, so we simply converted days into hours. Examples: 35. A certain radioactive isotope has a half-life of 2400 years. How many half-lives have past for a sample of this material collected 12,000 years ago? 12,000 years =5 half lives 2,400 years 36. Oxygen-21 has a half-life of about 3.5 seconds. How many half-lives will have passed after 14 seconds? 14 seconds =4 half lives 3.5 seconds 37. Rn-221 has a half-life of about 30 minutes. How many half-lives have passed after 4 hours? 240 min =8 half lives 30 min HALF-LIFE CALCULATIONS If we know the number of half-lives that have passed, determining how much of a radioactive material remains is as simple as dividing by two as many times as there are half-lives. For example, if I have 60 g of a radioactive isotope and 3 half-lives have passed: 1st half-life: 60 g/2 =30 g 2nd half-life: 30 g/2 = 15 g 3rd half-life: 15 g/2 = 7.5 g So, after 3 half-lives, we have 7.5 grams. Once we know the amount of half-lives, calculating how much of a radioactive substance remains is just that easy! One way to set this up is to draw a simple chart. We will use this method to solve the question: What % of an unstable isotope will remain after 4 half-lives? Number of half lives Amount remaining 0 (initial) 100 % 1 50 % 2 25 % 3 12.5% 4 6.25 % You just divide by two 4 times and get the final answer of 6.25 %. This means that after 4 half-lives, 6.25 % of this sample will remain. Now that you know how to calculate the number of half-lives and also know how to determine the amount remaining given the number of half-lives. Let us now put these skills together to determine the answer to questions such as: An isotope of Bismuth-214 has a half-life of 20 minutes. How many grams of a 16-gram sample will remain after 60 minutes? First, we determine the number of half-lives by dividing the total time by the half-life: total time =60 min =3 half lives half life 20 min Next, we use the half-life to divide the sample amount by two the number of times that we have half- lives. o 1st half-life: 16 g/2 = 8 g o 2nd half-life: 8 g/2 = 4 g o 3rd half-life: 4 g/2 = 2 g Therefore, two grams of Bismuth-214 will remain after 60 minutes. As we saw, the process of calculating half-life is a simple, two-step process. • Step 1: Calculate how many half-lives have passed • Step 2: Start with initial amount of sample and divide by two that many times Answer the following half live calculations: 38. An unstable isotope has a half-life of 3 days. How many kg of an 820 kg sample will remain after 6 days? 6 days 2half lives 3 days o 1st half-life: 820kg/2= 410 kg o 2nd half-life: 410kg/2= 205 kg 39. Neodymium-161 has a half-life of about 500ms. What % of a fresh sample of this material would I have after 1 second? o T1/2=500ms o T1/2=0.5 s Make sure both units of time are the same before dividing the total time by the half-life as usual. Starting at 100 %, we divide by two for each half life. In this case, there are 1000 ms/s, divided by 500ms = 2 half-lives, so after two half-lives 25% remains. RISKS OF RADIATION The radiation warning symbol, like the one pictured on the sign above, can help you to note potential sauces of radiation. While radiation has always been a part of our world, avoiding unnecessary exposure to ionizing radiation is important for our safety. Exposure to high levels of radiation can cause sickness and death while long term exposure to above average levels of radiation over time can lead to cancer and damage to reproductive health. POWER GENERATION Nuclear power is one of the first areas that often come to mind when considering the uses of radioactive materials. Nuclear energy is a relatively clean source of energy and has the potential to provide sustainable energy in many areas of the world. Nuclear power has faced defunding after a number of high-profile incidents; however, with the volatility of many sources of energy, the next generation of nuclear reactors is being researched. A common misconception with nuclear power plants is that the emissions are of radioactive material; however, the emissions, as seen in the image, are steam from the power generation process. An important consideration of nuclear power generation is what to do with the radioactive waste generated. Current methods involve burial in uninhabited barren areas away from sources of water or volcanic/seismic activity to prevent release into the environment. Other proposed technologies involve reusing nuclear waste for power generation. One interesting biproduct from nuclear power generation is nuclear isotopes that can be used in healthcare. NUCLEAR MEDICINE: NUCLEAR IMAGING Radioactive materials have many real worlds uses in the field of healthcare. These materials provide us with important diagnostic tools and treatments, and like any tools, must be treated with respect and used responsibly. In healthcare, the largest use of radioactive materials is in imaging; an area known as nuclear imaging. • PET (positron emission tomography) scans • X-ray imaging • Contrast agents (radioactive materials injected to increase the contrast of tissues when imaging) These and other imaging technologies allow for healthcare providers to better make medical judgments and improve patient outcomes in a less invasive way. The resolution of these scans has dramatically decreased the need for invasive surgery. For an individual receiving a medical scan, the benefits generally greatly outweigh the risks. The improved outcomes provided by accurate diagnosis, early detection, and avoiding exploratory surgery more than justify a short exposure to ionizing radiation. Precautions are also put into place to minimize exposure, including shielding of areas not being scanned and short exposure times. Each year, hundreds of thousands of medical scans are completed around the world safely. While an individual undergoing nuclear imaging is exposed to a small dose, those healthcare workers administering the scan take precautions to limit exposure to themselves over the long term. To avoid exposing themselves to the radiation from administering many scans each day, workers use shielding such as lead-lined rooms and track their exposure with radiation badges. NUCLEAR MEDICINE: THERAPY The field of nuclear medicine has allowed for advances in the treatment of many medical conditions. Radiation therapy is a general term for using radiation to treat an ailment. Examples of this include: • Gamma radiation used to eliminate tumors noninvasively • Brachytherapy (inserting “seeds” into tissue) used mainly in the treatment of prostate cancer • Iodine-131 used to treat hyperthyroidism or thyroid cancer As radiation therapy exposes a patient to far more ionizing radiation than a simple medical scan, the risks of these procedures are greater. Because of this risk, radiation therapy is generally limited to serious medical concerns such as cancer and other life-threatening conditions. Additionally, there is a limit to the amount of radiation a body can safely receive in a lifetime and each patient’s radiation exposure, both overall and per area of the body, are tracked. Radiation therapy can also require the patient to take precautions around others due to the fact that radiation therapy, depending on the type used, can make an individual shed radiation. Individuals undergoing radiation therapy are often asked to avoid prolonged exposure to other individuals, especially children, in the time frame they are undergoing therapy. Healthcare workers must also be aware of the risks when administering nuclear medicine. Healthcare workers use radiation badges to track exposure, administer treatments only in specific rooms, and use specialized personal protective equipment. OTHER USES OF RADIATION The examples we are exploring in this lesson are only a few of the many uses of radiation in our world. A few more examples of radiation used in our day to day lives include: • Smoke detectors • Smoke detectors use americium as a source of alpha particles between an emitter and a detector • When smoke is present, the flow of radiation is disrupted, and the alarm goes off. • Irradiation of food • Irradiation of food, typically with gamma radiation, kills microorganisms so that the food stays fresher longer • Does not cause the food to become radioactive • Airport scanners • X-Rays are used to check baggage for contraband • Geiger counters are also used to check that no radioactive materials are being brought onto planes Each of these is an example of the many ways that we use radiation in our day to day lives. One take home lesson is that radiation is a useful tool; however, we should be aware of our exposure and treat this tool with respect. 40. What % of a fresh sample of an unstable isotope with a half-life of 4 days remain after 8 days. Assume you start with 100%. o 6.25 % o 25 % o 50 % o 12.5 % 41. Rank the following applications of radioactive materials from highest exposure (top) to least exposure (bottom). 1. Radiation therapy with gamma radiation 2. Fully body PET scan 3. Hand X-ray 4. Smoke detector 42. Which of the following procedures would you expect to expose you to the least amount of radiation? o PET scan o Insertion of radioactive seeds into your body as a cancer treatment o Gamma treatment of a tumor o Use of radioactive iodine to treat an overactive thyroid 43. Au-180 has a half-life of 8 seconds. How much of a 60-gram sample will remain radioactive after 32 seconds? o 3.75 g o 7.5 g o 15 g o 30 g BIOLOGICAL POLYMERS In this lesson, we will shift our focus to biochemistry by discussing the concept of polymerization of monomers. This is the foundation for building macromolecules and cells. We briefly mentioned condensation reactions in the organic lessons and will see how condensation reactions play a role in this process. 44. In condensation reactions, what small molecule is produced as a by-product? o Hydrogen gas o Acids o Methane o Water MONOMERS AND POLYMERS Biochemistry is the study of how organisms use molecules for life processes. Many of the molecules used to build cells are polymers. The word polymer means “many parts.” These polymers are formed from monomers, meaning “one part.” Monomers are small units of the larger polymers. As part of normal processes called metabolism, your body can build polymers (anabolism) or break polymers into their components (catabolism). Every time you eat a delicious meal, your body is breaking down the large polymers to recycle them into monomers. Your body’s chemistry can then rearrange those monomers to form different polymers. For example, a toy brick model of a car would be considered a polymer because it is made of many monomers. The monomers are the individual toy bricks. If the car is torn down (catabolized), the monomers can then be used to build a brick castle instead (anabolism). Polymers are found in our everyday lives. Items such as polystyrene, also known as Styrofoam, are made from styrene monomers. Silk is a polymer made naturally from amino acid monomers, as is cotton. Rubber is a polymer made from the monomer isoprene. Polymers found in your body that will be discussed in later lessons are: • carbohydrates, made of monosaccharide monomers • proteins, made of amino acid monomers • nucleic acids, made of nucleotide monomers These are the macromolecules (“macro” meaning “large”). 45. Answer the following questions about monomers and polymers o Monomers are small molecules used to build large molecules called Polymers o Which of the following is not an example of a polymer? o silk o styrene o rubber o proteins o cotton o Condensation reactions are involved in reactions o Catabolic o Combustion o Anabolic o Neutralization o Transfer CONDENSATION REACTIONS When polymers are built from monomers (anabolism) they undergo condensation reactions. Condensation reactions in natural polymers occur between functional groups such as carboxylic acids, alcohol, and amines. The primary by-product of this reaction is a small molecule, often water. The two functional groups will react with each other, releasing a molecule of water. This leaves unpaired atoms, which then bond with each other to fulfil their octet valence electron requirements. The only portion of the molecule that is affected by the reaction are the atoms involved in forming water; all other atoms in the molecule retain their bonds. As shown in previous lessons, condensation reactions form new functional groups such as ethers and esters. The condensation of two alcohols forms an ether; the condensation of an alcohol and a carboxylic acid forms an ester. Condensation reaction of ethanoic acid and butanol to form an ester. The hydroxyl groups of the alcohol and carboxylic acid will react to release one molecule of water; the remaining oxygen will form a new bond to the carbon chain, joining the ethanoic acid and butanol carbon chains. Similarly, the basic amine can condense with the acidic carboxylic acid, releasing water in its condensation reaction. This forms an amide bond, which is how proteins are formed from amino acids. Condensation reactions always have at least one monomer as a reactant, and always have water as a product and a combination of the molecules, the polymer, as the second product. The example above shows two monomers reacting to form a dimer (meaning “two parts”); however, a longer polymer chain may also react via condensation with a monomer. This happens in the formation of long-chain polymers, which are built by adding one monomer at a time. 46. Arrange the following by size, from smallest on the top largest on bottom o Monomer o Dimer o Polymer MONOMER IN A CONDENSATION REACTION The following monomer is involved in a condensation reaction. Click the plus to see the portion that will remain unchanged. Condensation Reaction Alcohol, amine, and carboxylic acid groups can combine in condensation reactions. In this example, the – OH of the hydroxyl group will be used in the condensation reaction, and the remainder of the molecule will remain unchanged. HYDROLYSIS REACTIONS When polymers break down during catabolism, hydrolysis reactions occur. In hydrolysis reactions, a molecule of water is used to break a bond, separating the monomers. These reactions are essentially the reverse of condensation. To complete this reaction, the electrons on the electronegative oxygen in water will attach to the polymer. This attachment causes the existing bond between the monomers to break, releasing the two separated monomers. This follows the law of conservation of mass, by rearranging the bonding of the atoms present to form new products. In these reactions, the substrates are polymers and water, which then form monomers as the product. 47. Answer the following questions about hydrolysis reactions o In condensation reaction, a water molecule is produced when a bond is formed. In hydrolysis reactions, a water molecule is used when a bond is broken. o Determine if the statement applies to hydrolysis or condensation reactions. Condensation Hydrolysis Monomers are used to form polymers X Polymers are broken down to form monomers X Water is a product X Water is used as a substrate X 48. Select the letter next to the circled portion of the molecule that will react in a condensation reaction. o A o B o C o D 49. Determine if the statement is true for hydrolysis or condensation. Condensation Hydrolysis Monomers are a product X Monomers are a substrate X Bonds are formed X Bonds are broken X 50. Which portion of this molecule represents a carboxylic acid? o A o B o C o D 51. Hydrolysis reactions are involved in reactions. o transfer o catabolic o neutralization o combustion o anabolic 52. Hydrolysis involves… o Water molecules as a substrate o Polymers breaking apart o Formation of polymers o A and B only o A, B, C are correct 53. are larger than . o Dimers/polymers o Dimers/monomers o Monomers/dimers o Monomers/polymers 54. Examples of polymers include o Proteins o Carbohydrates o Silk o All of the above o None of the above CARBOHYDRATES In this concept, we will discuss one class of biological polymers called carbohydrates. You might be familiar with this class of biopolymers, as they are fruits, grains, and other sweet additions to your daily diet. After completing this lesson, you will be able to • Describe how the composition, structures, and properties of carbohydrates relate to their functions. • List common examples of monosaccharides, disaccharides and polysaccharides. 55. Which of the following is a source of carbohydrates? o Sugar, fruits, and bread o Butter and oils o Steaks o Water STRUCTURES AND PROPERTIES OF CARBOHYDRATES Carbohydrates are an important source of energy in our bodies. They contain many -OH groups (alcohol groups, also known as hydroxyl groups) and contain a carbonyl functional group: either aldehyde or a ketone. We see examples of these in the world around us. Examples include table sugar, starch, and even wood. The simplest of these carbohydrates are known as monosaccharides. These simple sugars can be linked together to form more complex carbohydrates: disaccharides and polysaccharides. Carbohydrates are found throughout cells, both inside and outside. This class of macromolecules is used for energy, energy storage, structure, and cell recognition. These molecules are water soluble and can move into cells to provide energy. When formed into long chain polymers, they can store energy for future use in the cell such as starch in plants, and glycogen in humans. In plant cells, carbohydrate polymers called cellulose form rigid protective structures called the cell wall. Human cells do not contain cell walls, but sugar molecules are found on the surface of our cells as recognition such as on the surface of blood cells; these carbohydrate markers give us blood types A, B, AB, and O. When incompatible blood types are mixed, the blood will coagulate. Image of a cell wall in plants. This cell wall contains the carbohydrate polymer cellulose, which is rigid and provides structure to plant cells. Sugar molecules on the surface of red blood cells give the different blood types: A, B, AB, and O. 56. Answer the following questions about the structures and properties of carbohydrates. o Carbohydrates are not used for o Cell recognition o Energy storage o Catalysis o Cell walls o Carbohydrates contain functional groups. o Alcohols o Ketones or aldehydes o Amine o Carboxylic acid o Halogens o When formed into long chain polymers, they can store energy for future use in the cell such as starch in plants, and glycogen in humans. In plant cells, carbohydrate polymers called cellulose form rigid protective structures called the cell wall. MONOSACCHARIDES, DISACCHARIDES, AND POLYSACCHARIDES The basic carbohydrate unit is the monosaccharide. Monosaccharides are simple sugars that have an unbranched chain of 3-8 carbon atoms and are classified as either an aldose or a ketose. Aldoses contain an aldehyde, whereas ketoses contain a ketone. Most of the time, monosaccharides exist in a ring structure that has formed when the carbonyl and a hydroxyl group on the same molecule have reacted. Aldoses will typically form hexagon cyclic structures, and ketoses will typically form pentagon cyclic structures. By remembering the mnemonic “Mona Gladly Fruits the Gallon” you can remember three common monosaccharides: • Monosaccharides are glucose, fructose, and galactose. These three carbohydrates are isomers; they have the same molecular formula but differ in the arrangement of the functional groups. They all have the formula C6H12O6. A common monosaccharide is glucose. Glucose is an aldose and is found in many sources and is the major carbohydrate of energy. This molecule is used in the first step of the energy making process, and many energy storage polymers are made from glucose monomers. Glucose forms a six-membered cyclic hexagon in solution. Cyclic Structure of Glucose Fructose is commonly found in fruits and is sometimes called fruit sugar. When combined with glucose, fructose will be used to form the disaccharide sucrose. In nature, this forms a five-membered pentagon ring. Cyclic Structure of Fructose Galactose is also called “cerebrose” or “brain sugar.” When combined with glucose, galactose will be used to form the disaccharide lactose. Galactose will form a hexagon in solution, similar to glucose. 57. Classify the molecules as aldoses or ketoses: o Glucose  Aldose o Fructose  Ketose o Galactose  Aldose 58. Select all that apply. Monosaccharides include o Sucrose o Lactose o Glucose o Fructose o Cellulose DISACCHARIDES AND POLYSACCHARIDES A disaccharide forms when the hydroxyl group from one monosaccharide reacts with the hydroxyl group of another monosaccharide in a condensation reaction. One molecule of water is released when this glycosidic bond, an ether, forms. The table sugar that you most likely have in your kitchen, sucrose, C12H22O11, is a disaccharide that is composed of one molecule of glucose and one molecule of fructose. The mnemonic to remember common disaccharides is “Diana wears Small, Medium, and Large.” • Disaccharides are Sucrose, Maltose, and Lactose Sucrose is made when one molecule of glucose condenses with one molecule of fructose. This is common table sugar. Maltose is made when two molecules of glucose combine. Maltose Lactose is made from one molecule of glucose and one molecule of galactose. This is found in milk, and some people cannot digest this disaccharide in a condition known as “lactose intolerance.” A polysaccharide is a polymer of many monosaccharides joined through condensation reactions. Common polysaccharides include amylose, amylopectin, glycogen, and cellulose. These are all polymers of glucose and used for energy storage as well as cell structures. The mnemonic to remember is “Poly Starts Cello Glyding.” • Polysaccharides are starch, cellulose, and glycogen. Starch is the storage molecule in plants, and glycogen is the storage molecule in animals. Cellulose is the polymer that gives cell walls their rigid shape and structure. 59. Arrange the following by number of monomers, from smallest number to monomers on top to smallest numbers on the bottom o Glucose o Maltose o Glycogen 60. Complete the following sentences o The main component of table sugar is sucrose, made of one molecule of glucose which forms a six-member ring in nature, and one molecule of fructose, also known as fruit sugar. o The disaccharide found in milk is lactose, made of the monosaccharide galactose that is also known as brain sugar and glucose which is the prominent monosaccharide for energy. The disaccharide maltose is made of two molecules of glucose. Glycosidic Bond in the following disaccharide 61. For each disaccharide, chose the monomer(s) that are joined in the disaccharide. Fructose Galactose Glucose Lactose X X Sucrose X X Maltose X 62. Where will you find sucrose? o Storage of energy in plant cells o Storage of energy in animal cells o Table sugar o Plant cell walls 63. Select all that apply. Carbohydrates can be used for which of the following cellular functions: o cell recognition o cell walls o information storage o used for energy o energy storage 64. Carbohydrates can contain functional groups: o Alkene o Aldehydes o Glycosidic o Alcohols o Ketones 65. Select the correct letter corresponding to the circled glycosidic bond in the structure A 66. Which monomers are used to form maltose? o Glucose o Fructose o Galactose o Glycogen o Lactose 67. Determine if the molecule is monosaccharide, disaccharide, polysaccharide Monosaccharide Disaccharide Polysaccharide Lactose X Fructose X Cellulose X Sucrose X [Show More]

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