Education is a long road that lasts a lifetime. Follow the WORLD MAKERS learning path to create a more equal, fair and sustainable world. Learning path The atom 4 L E T ' S G E T S TA R T E D Write the screenplay for a radioactive series L E A R N I N G S I T UAT I O N Chernobyl nuclear power station , Ukraine, April 1986. During a test, an accident caused one of the nuclear reactors to explode. An endless number of radioactive particles polluted the atmosphere, water, vegetation , animals and the people living nearby. Humans will not be able to inhabit this region again for many years. In 2019, a TV series about this accident was released . Would you like to write the screenplay of a series where nuclear energy has the leading role? In this unit we will help you to do it. Take act ion As you write the screenplay for the series, you will learn about radioactivity and some of its applications. You will study the characteristics of radioactive waste and how it must be managed to achieve this target of the SDGs. Target 12.4: "By 2030, achieve the environmentally sound management of chemicals and all wastes throughout their life cycle […] and significantly reduce their release to air, water and soil in order to minimise their adverse impacts on human health and the environment." What is an atom? What particles form atoms? What is the relationship between atoms and electricity? What is nuclear energy? What other types of energy do you know? Describe them. WORK WITH THE IMAGE Look at the photo on the previous page. In 2016, a massive 30 000-tonne steel structure was constructed to cover the remains of the Chernobyl nuclear reactor. It cost 1.5 billion (1 500 000 000) euros. Why was it built, if it has been several decades since the accident? The structure was assembled in a separate place. Then it was taken to its final location and placed over the reactors. What could be the reason for this? Why do you think steel was used instead of wood or aluminium to cover the reactor? Look at the photo on the left. Why do people who work with radioactive waste wear special suits? IN THIS UNIT… Atoms. Atomic models The particles that make up atoms Advances in the atomic model Atoms, isotopes and atomic mass Atoms and electricity Ions: anions and cations Radioactivity CHALLE NGE 83 82 ES0000000137418 183391_Unidad04_111062.indd 82-83 18/7/22 13:30 WHAT IS MATTER MADE UP OF? Ever ything around us is made up of atoms. ATOMS AND ELECTRICITY Certain materials become electrically charged when rubbed together. Two types of forces appear between them. RADIANT ENERGY Radiant energy is the energy in electromagnetic radiation . When an object is rubbed , its atoms can gain or lose electrons and acquire a negative or positive electric charge, respectively. PHYSICS AND CHEMISTRY REVISION 1 Classify the particles that make up the atom according to whether they are in the nucleus or shell. 2 Look at the energy diagram and the types of electromagnetic radiation. Describe an application or device that is used regularly for each type. 3 Do an experiment to test whether various materials become electrically charged when rubbed together. Rub a plastic pen on your jumper and attract small pieces of paper with it. Then rub it with something made of cotton. Now do the same with a wooden pencil instead of the plastic pen. A C T I V I T I E S + Proton : particle with a positive electric charge Neutron : particle with no electric charge - Electron : particle with a negative electric charge Repulsion Attraction Two pieces of electrically charged glass repel . Two pieces of electrically charged amber repel . Electrically charged glass and amber attract. ENERGY Radio waves Microwaves Infrared Visible Ultraviolet X-rays c rays 2 oxygen atoms 2 nitrogen atoms Silicon atoms 2 hydrogen atoms and 1 oxygen atom Carbon atoms Aluminium atoms Shell Nucleus STRUCTURE OF AN ATOM 84 ES0000000137418 183391_Unidad04_111062.indd 84 18/7/22 13:33 Mass Electric charge Proton 1 u +1 e Electron 1 / 1 836 u -1 e Neutron 1 u 0 3 10 Calculate how many protons we need for the total mass to be 1 kg. And neutrons? And electrons? 11 Calculate how many protons we need for the total electric charge to be 1 C. And electrons? A C T I V I T I E S 2.2. The atomic scale As protons, neutrons and electrons are ver y small particles, when working with atoms, it is common to use the atomic scale. This uses the approximate mass and charge of a proton as units of mass and charge. S O LV E D P R O B L E M 1 Calculate the mass and charge of the atom in the image. Write the result in SI units and in the atomic scale. 1. Count the particles of each type in the atom. Protons: 2 Neutrons: 3 Electrons: 2 2. Find the mass and charge data of each particle. Make a table with the number of particles and the mass and charge calculations of each particle type in SI units. Then calculate it for the whole atom. Particles Number Mass (kg) Charge (C) Proton 2 2 ? 1.673 ? 10-27 = 3.346 ? 10-27 2 ? (+1.6 ? 10-19) = +3.2 ? 10-19 Neutron 3 3 ? 1.675 ? 10-27 = 5.025 ? 10-27 3 ? 0 = 0 Electron 2 2 ? 9.11 ? 10-31 = 1.822 ? 10-30 2 ? (-1.6 ? 10-19) = -3.2 ? 10-19 Total for the atom 8.373 ? 10-27 0 The mass of the atom is 8.373 ? 10-27 kg and its charge is 0 C. 3. Repeat the previous step using atomic units. Particles Number Mass (u) Charge (e) Proton 2 2 ? 1 = 2 2 ? (+1) = +2 Neutron 3 3 ? 1 = 3 3 ? 0 = 0 Electron 2 2 ? 0* = 0 2 ? (-1) = -2 Total for the atom 5 0 The mass of the atom is 5 u and its charge is 0 e. unit of atomic mass (u): unit of atomic charge (e): 1 u = 1.66 ? 10-27 kg 1 e = 1.6 ? 10-19 C * In units of atomic mass, we can consider the mass of the electron to be zero. 87 ES0000000137418 183391_Unidad04_111062.indd 87 18/7/22 13:34 LEARNING SITUATION. THE CHALLENGE 1 THE SUSTAINABLE DEVELOPMENT GOALS 2 CORE SKILLS 3 Remember what you already know about the topic, your previous knowledge acquired in previous years, in other units or in your own daily life. Think about an everyday life situation and put yourself in the place of the characters who present it. Contribute to the achievement of one or several targets of the Sustainable Development Goals (SDGs). Analyse examples of SOLVED PROBLEMS, then apply what you have learnt to solve the activities. Think and express your analytical side by doing the different ACTIVITIES. Critical thinking. Discuss whether the information is true or not. In the TRUE OR FALSE? section, you will find suggestions for learning how to create truthful content and for deconstructing fake news and myths. Review in the initial REVISION section what you already know and relate this knowledge to what you are going to learn. Research, think and then answer the questions that will help you complete the challenge and acquire core skills. 3. Advances in the atomic model 12 Why do we get different coloured flames when we burn substances made up of different chemical elements? What is the atomic model that explains this behaviour of atoms? 13 Which is greater, the amount of energy emitted when an electron changes level in an atom, or the energy emitted by an atom of a radioactive element? Identify chemical elements by the colour of a flame An atom is so small that it is impossible to see it directly. One way of detecting the presence of atoms of a certain chemical element is to do a flame test. Beaker of water Spatulas Substances to analyse Glass rods Containers, spatulas and glass rods Flammable alcohol (methanol or ethanol) Long-handled lighter Substances to analyse: – Sodium carbonate, Na2CO3 – Copper dichloride, CuCl2 – Potassium bromide, KBr 1. Put some of the substance you are going to analyse into a clean crucible with the tip of a spatula. 2. Add between 3 and 5 mL of alcohol and stir it with the glass rod. 3. Light the flame of the lighter at the edge of the crucible. 4. Observe the colour of the flame. At first it will be blue, because of the alcohol. Then it will change. Stir it from time to time with the glass rod to revive the flame. 5. Wait for the flame to go out, or put it out with water. 6. Search for information about the flame test and identify which chemical element corresponds to the colour of each flame. Steps Sodium carbonate Copper dichloride Potassium bromide All the materials must be very clean, so that products are not contaminated with other products. Be careful not to spill alcohol onto the table. If any alcohol is spilt, clean it well before lighting a flame. If you perform more than one analysis at a time, make sure that the crucibles are far away from each other, so that the flames do not touch. Have a large beaker of water ready in case flames from the crucibles get out of control. Crucibles Materials CHALLENGE 88 ES0000000137418 183391_Unidad04_111062.indd 88 18/7/22 13:49 3 Are microwave ovens radioactive? The energy of the microwaves makes the water molecules inside the food vibrate, which generates heat and cooks the food . Microwaves are ref lected by the metallic parts inside so that they spread in all directions and reach the food . Microwave ovens generate electromagnetic radiation , similar to a mobile phone, a radio, or sunlight. Microwave ovens are not radioactive! 48 Spain pays around 75 000 € per day to France for storing our nuclear waste. However, some Spanish nuclear power stations have their own pools to store waste. a) What type of waste is collected in the pools in nuclear power stations: very low, low, medium or high level? b) Investigate how that high daily payment for storing nuclear waste could be avoided. 49 Hospital radiology departments often employ people with a knowledge of nuclear physics or chemistry. a) Why do you think these people work there even though they have not studied Medicine? What do you think their job involves? b) What precautions should be observed in a hospital where radioactive isotopes are used in the diagnosis or treatment of diseases? A C T I V I T I E S This is not harmful to living things, but it can sometimes cause interference with other types of radiation , such as a wi-fi network. Unlike a mobile phone, in a microwave oven the waves are concentrated in an enclosed space. The ovens emit low levels of microwave radiation , although they are protected . T R U E OR FALSE ? RESTRICTED ACCESS RISK OF RADIATION 101 ES0000000137418 183391_Unidad04_111062.indd 101 18/7/22 13:34 Do experiments and carry out simple practical activities. Complete the steps by applying what you have learnt. Acquire essential knowledge from content explained in a very clear way and with strong visual support: photos, drawings, diagrams, etc. Mass 9.11 ? 10-31 kg Charge -1.6 ? 10-19 C Electron Mass 1.675 ? 10-27 kg Charge 0 Neutron Mass 1.673 ? 10-27 kg Charge +1.6 ? 10-19 C Proton The unit for electric charge in the SI is the coulomb (C). 2. The particles that make up atoms 7 What mass do the particles that make up atoms have? Which have a greater mass? 8 Are these particles electrically charged? How can atoms be neutral? 9 Do you think that the size of the particles in the atom made it difficult to study nuclear energy, compared to other sources of energy, such as wind or water energy? Why? By comparing the mass of the proton and the electron , we obtain : . . ? ? m m 9 11 10 1 673 10 1836 kg kg electron proton 31 27 = = - - " mproton = 1 836 ? melectron The mass of the proton is 1836 times greater than the mass of the electron , just as the mass of a giraf fe is about 1 836 times greater than that of a guinea pig. The mass of the proton is ver y similar to that of the neutron . The mass of the electron is much less than that of the proton and neutron . The charge of the electron is the same as the charge of the proton , but with the opposite sign . The atom is neutral , so it must have the same number of protons as electrons. The number of neutrons is similar to the number of protons, but it does not have to be the same. CHALLENGE All the matter around us is made up of atoms. 2.1. Properties of the particles that make up atoms In 1932, it was discovered that in the nucleus of atoms there is a particle that has no electric charge. It was called the neutron. Various investigations enabled us to know the mass and electric charge of the particles present in the atom. 86 ES0000000137418 183391_Unidad04_111062.indd 86 18/7/22 13:33 ESSENTIAL KNOWLEDGE 4
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