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 L E A R N I N G S I T UAT I O N In recent years, molecular gastronomy has brought ver y innovative utensils and techniques into the kitchen . Chefs almost appear to be working in a physics and chemistr y laborator y. And this is what molecular gastronomy consists of: applying scientific knowledge to understand and explore culinar y possibilities. A knowledge of gases and mixtures of substances is essential to many spectacular dishes. And comprehensive knowledge goes hand in hand with the scientific method . Take act ion As you write the report and apply the scientific method , you will learn the steps that rigorous work requires, from planning it to publishing the results. This will help you to become a valuable professional , and you will be able to contribute to sustainable development. Target 4.4: "By 2030, substantially increase the number of youths and adults who have relevant skills, including technical and vocational skills, for employment, decent jobs and entrepreneurship." Matter: gases and solutions 1 Most of the matter around us is in a solid, liquid or gaseous state. Which of the following characteristics correspond to each state? • It has a fixed shape. • It has a fixed volume. • It can be compressed. • It expands. • It needs to be in a container to handle it (say whether the container is open or closed). What is a homogeneous mixture? What about a heterogeneous mixture? Give examples, indicating which substances make up the mixture in each case. WORK WITH THE IMAGE Imagine that this glass has been left on a table to observe how it evolves over time. In what physical state is the glass? What about the red matter? And the white matter? Why is the white matter coming out of the glass? Will all the white matter come out of the glass? Will we stop seeing it as white matter? Explain what is happening to it. Will room temperature influence the process? L E T ' S G E T S TA R T E D IN THIS UNIT. . . Gases The gas laws. The BoyleMariotte law. Gay-Lussac's law. Charles' law The general ideal gas equation The ideal gas equation of state The kinetic theory of gases Solutions Write a scientific report, applying the scientific method CHALLE NGE 9 8 WHAT MAKES UP MATTER? ATOMS PHYSICS AND CHEMISTRY REVISION Made up of several substances Several distinguishable components Same type of atoms The components are indistinguishable Made up of a single substance Different types of atoms Homogeneous or solutions Heterogeneous Simple substances Atoms are the building blocks of all matter. Currently, 118 dif ferent types of atoms are known . These atoms make up each of the 118 chemical elements. Compounds MATTER The symbol of the element it belongs to is the first letter of the Latin name of the element. The mass number, A, is the number of protons plus the number of neutrons. The atomic number, Z, indicates the number of protons. If the atom is neutral , it coincides with the number of electrons. O A Z X 16 8 + Proton : particle with a positive electric charge Neutron : particle with no electric charge - Electron : particle with a negative electric charge Shell Nucleus Mixtures Pure substances 1 Use the periodic table in the annex to complete the following table in your notebook. (P: no. of protons; E: no. of electrons; N: no. of neutrons.) Name Symbol Z A P E N A Bromine 80 35Br 35 80 35 35 45 B ... ... 18 40 ... ... ... C ... 190 76Os ... ... ... ... ... D Barium ... ... 137 ... ... ... E ... ... ... ... 63 ... 89 F ... 23 11Na ... ... ... ... ... G Thorium ... ... ... ... ... 142 H ... ... 207 82 ... ... A C T I V I T I E S 36 1 Relate hot-air balloon flights to Charles' law The history of hot-air balloons is closely related to Jacques Charles. His studies made it possible to calculate the volume increase that a gas experiences when it is heated to a certain temperature, keeping it at atmospheric pressure. How is the flight of a hot-air balloon controlled? • Some hot-air balloons are made of a flexible material. In some balloons a gas that is lighter than air is used. This was hydrogen at first, but today it is helium. • When heated, the temperature of the gas increases and it expands. As the hot-air balloon and its gas are in the atmosphere, the process is performed at a constant pressure (atmospheric pressure). Volume and temperature are directly proportional (Charles' law). • The balloon, with the hot gas, is less dense than air, and can ascend and keep itself in flight. • To descend, the gas is no longer heated. The temperature decreases and, with it, the volume in the same proportion. • The density of the air in the balloon gradually increases and the balloon can descend. SOLVED PROBLEM 4 In a kitchen, where the temperature is 30 °C, there is a bottle partially filled with water. The free space of 200 mL is occupied by a gas. We put it in the fridge, where the temperature is 4 °C. What volume does the gas in the bottle occupy? If the bottle is made of soft plastic, what happens to it? 1. Write the two states of the gas with their quantities. p1 = 1 atm V1 = 200 mL T1 = 30 °C p2 = 1 atm V2 = ? T2 = 4 °C 2. Identify the law to apply. For a transformation when p = constant, apply Charles’ law. V T V T 1 1 2 2 = 3. Make V2 the subject. V T V T V T V T V T T V 1 1 2 2 1 2 2 1 2 2 1 1 = → ⋅ = ⋅ → = ⋅ 4. Before substituting the data, write all the amounts of each quantity in the same units. The temperature must be in kelvin: T1 (K) = T1 (°C) + 273 = 30 °C + 273 = 303 K T2 (K) = T2 (°C) + 273 = 4 °C + 273 = 277 K Apply Charles’ law: V T T V 2 2 1 1 182 8 = = = ⋅ ⋅ 277 K 303 K 200 mL . mL The gas occupies a smaller volume. If the bottle is soft plastic, it will get crushed. 12 A balloon occupies a volume of 1 m3 at a temperature of 20 °C. The gas inside is heated to 100 °C. What will be its volume now if the process took place at atmospheric pressure? 13 Explain whether this is true: “When a gas experiences transformations at a constant pressure, its volume and temperature are directly proportional. That is, if its temperature goes from 20 °C to 40 °C, its volume also doubles.” A C T I V I T I E S 17 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. 4. Gas laws. Charles' law Simulate the behaviour of gases Steps This application allows you to simulate the behaviour of gases. You can reproduce experiments to see the effect of temperature on particle velocity, deduce laws, etc. It is found at phet.colorado.edu. 14 Simulate the conditions in which a gas experiences transformations at V = constant, p = constant and T = constant. In each case, complete a table of data for the independent variable and the dependent variable. Draw a graph of the data and deduce the corresponding law. Conclusions 1. Choose the study of Laws. 2. Select the quantity that will remain constant. 3. Select whether you want to display the Width of the container (to give an idea of the volume), the Stopwatch and the Collision Counter (to give an idea of the pressure). 4. Move the piston up and down one or more times to allow particles to enter the gas chamber. 5. Move the slider up or down to make the temperature hotter or colder. The temperature of the container will change accordingly (you can display it in °C or in K). 6. Read the resulting pressure (you can choose to display it in kPa or atm). Options for studying transformations at a constant pressure. You can change the volume of the container by var ying the width . 2 5 5 6 4 1 3 18 1 Can spray paints explode? Spray cans contain gas at a high pressure (between 2 and 8 atm) that helps to get the contents out. These cans are metal containers, so the gas is at a constant volume. If they are placed near a heat source, the gas heats up and its pressure increases (Gay-Lussac’s law). The pressure can be so high that the walls of the can cannot support it and it explodes. If a can of spray paint is thrown into a fire, it can explode! SOLVED PROBLEM 3 When a 500 mL can of spray paint is empty, the gas inside exerts a pressure of 1 atm at room temperature, which is 20 °C. If it is placed near fire, it can reach 800 °C. What pressure will the gas exert at that time? 1. Write down the two states of the gas with their quantities. p1 = 1 atm V1 = 500 mL T1 = 20 °C p2 = ? V2 = 500 mL T2 = 800 ºC 2. Identify the law to apply. For a transformation when V = constant, apply Gay-Lussac’s law. p T p T 1 1 2 2 = 3. Make p2 the subject. p T p T p T p T p T T p 1 1 2 2 1 2 2 1 2 2 1 1 = → ⋅ = ⋅ → = ⋅ 4. Before substituting the data, write all the amounts of each quantity in the same units. The temperature must be in kelvin: T1 (K) = T1 (°C) + 273 = 20 °C + 273 = 293 K T2 (K) = T2 (°C) + 273 = 800 °C + 273 = 1073 K Apply Gay-Lussac’s law: p T T p 2 2 1 1 = = = ⋅ ⋅ 1073 K 293 K 1 atm 3.7 atm 8 A 700 cm3 rigid container was filled with nitrogen gas. The manometer indicated a pressure of 100 kPa at 25 °C. What temperature will the gas be if the manometer indicates a pressure of 5 atm? 10 The manometer on a 100 L cylinder indicates that the gas inside it exerts a pressure of 1 atm at room temperature (20 °C). What pressure will it exert when its temperature reaches 130 ºC? 9 Pressure cookers cook food faster and with less water. At the high pressure inside, water boils at over 100 °C. Look at the diagram and answer: a) What type of matter is in the space above the fill limit line? What state is it in? b) Why does it have an airtight lid? c) Explain the function of the vent pipe and the safety valve. What could happen if it didn’t have them? d) It is necessary to check that the valves are not blocked, due to the risk of explosion. Use Gay-Lussac’s law to explain why it could explode. A C T I V I T I E S Vent pipe (releases steam when the pressure reaches the limit) Safety valve Airtight lid Fill limit line T R U E OR FALSE ? 15 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. The electronic configuration of an atom is the way in which its electrons are distributed around the nucleus. It follows three principles. The electronic configuration of an atom can be represented in various ways. Look at the example of a sulphur atom (Z = 16). The electronic configuration of an atom can also be written by taking the nearest previous noble gas and adding the atom's valence electrons. Valence electrons are the electrons of the outermost layer of an atom. 3. The distribution of electrons in atoms 16 Choose a chemical element whose atomic number means something to you, such as your age or your shoe size. Make a poster showing its symbol and electronic distribution. The auf bau's principle of minimum energy Electrons occupy the lowest energy orbital available. The energy order of the orbitals does not coincide exactly with the order of the levels and sub-levels. Moeller's diagram is used to establish the correct order. This is a simple mnemonic tool that helps us remember the order, and it does not follow the laws of physics. The diagram only shows the dif ferent types of orbitals. Square 2p represents the three p orbitals; square 3d represents the five d orbitals; and square 4f represents the seven f orbitals. Pauli 's exclusion principle In 1922, the spin of electrons was discovered . It was proved that this quantity can only have two values, represented by vertical arrows, one pointing up and the other pointing down . According to the exclusion principle, no two electrons in the same atom can be in the same state. Therefore, no more than two electrons can occupy the same orbital and they must have opposite spins. Hund 's rule of maximum multiplicity The most stable electronic configuration is the one with the most electrons with the same spin (called unpaired electrons). If there are three electrons in three p orbitals with the same amount of energy, each electron will occupy a p orbital . All three electrons will have the same spin. 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 7p 3d 4d 5d 6d 7d 4f 5f 6f 7f An electron's spin is represented by an arrow pointing up or down . Maximum number of electrons in each sub-level . Sub-level No. of electrons s 1 orbital ® 2 p 3 orbitals ® 6 d 5 orbitals ® 10 f 7 orbitals ® 14 1s 2s 2p 3s 3p S (Z = 16): 1s2 2s22p6 3s23p23p13p1 n = 3 n = 2 n = 1 1s 2p 3p 2s 3s Start: lowest energy Each arrow represents an electron. CHALLENGE Element Z Electronic configuration Ne 10 1s2 2s22p6 S 16 1s2 2s22p6 3s23p4 = [Ne] 3s23p4 46 ESSENTIAL KNOWLEDGE 4
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