Science 10 Science – Grade 10 Quarter 4 – Module 13: Law of Conservation of Mass and Balancing Chemical Equations First Edition, 2020 Republic Act 8293, section 176 states that: No copyright shall subsist in any work of the Government of the Philippines. However, prior approval of the government agency or office wherein the work is created shall be necessary for exploitation of such work for profit. Such agency or office may, among other things, impose as a condition the payment of royalties. Borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc.) included in this module are owned by their respective copyright holders. Every effort has been exerted to locate and seek permission to use these materials from their respective copyright owners. The publisher and authors do not represent nor claim ownership over them. Published by the Department of Education Division of Pasig City Development Team of the Self-Learning Module Writer: Deborah C. De Jesus Editors: Jeric N. Estaco Reviewers: Jeric N. Estaco/ Liza A. ALvarez Illustrator: Layout Artist: Jean Rean M. Laurente Management Team: Ma. Evalou Concepcion A. Agustin OIC-Schools Division Superintendent Carolina T. Rivera OIC-Assistant Schools Division Superintendent Manuel A. Laguerta, EdD OIC-Chief, Curriculum Implementation Division Education Program Supervisors Librada L. Agon EdD (EPP/TLE/TVL/TVE) Liza A. Alvarez (Science/STEM/SSP) Bernard R. Balitao (AP/HUMSS) Joselito E. Calios (English/SPFL/GAS) Norlyn D. Conde EdD (MAPEH/SPA/SPS/HOPE/A&D/Sports) Wilma Q. Del Rosario (LRMS/ADM) Ma. Teresita E. Herrera EdD (Filipino/GAS/Piling Larang) Perlita M. Ignacio PhD (EsP) Dulce O. Santos PhD (Kindergarten/MTB-MLE) Teresita P. Tagulao EdD (Mathematics/ABM) Printed in the Philippines by Department of Education – Schools Division of Pasig City Science 10 Quarter 4 Self-Learning Module 13 Law of Conservation of Mass and Balancing Chemical Equations Introductory Message For the facilitator: Welcome to the Science 10 Self-Learning Module on Law of Mass Conservation and Balancing Chemical Equations. This Self-Learning Module was collaboratively designed, developed and reviewed by educators from the Schools Division Office of Pasig City headed by its Officer-in-Charge Schools Division Superintendent, Ma. Evalou Concepcion A. Agustin, in partnership with the City Government of Pasig through its mayor, Honorable Victor Ma. Regis N. Sotto. The writers utilized the standards set by the K to 12 Curriculum using the Most Essential Learning Competencies (MELC) in developing this instructional resource. This learning material hopes to engage the learners in guided and independent learning activities at their own pace and time. Further, this also aims to help learners acquire the needed 21st century skills especially the 5 Cs, namely: Communication, Collaboration, Creativity, Critical Thinking, and Character while taking into consideration their needs and circumstances. In addition to the material in the main text, you will also see this box in the body of the module: Notes to the Teacher This contains helpful tips or strategies that will help you in guiding the learners. As a facilitator you are expected to orient the learners on how to use this module. You also need to keep track of the learners' progress while allowing them to manage their own learning. Moreover, you are expected to encourage and assist the learners as they do the tasks included in the module. For the Learner: Welcome to the Science 10 Self-Learning Module on Law of Mass Conservation and Balancing Chemical Equations. This module was designed to provide you with fun and meaningful opportunities for guided and independent learning at your own pace and time. You will be enabled to process the contents of the learning material while being an active learner. This module has the following parts and corresponding icons: Expectations - This points to the set of knowledge and skills that you will learn after completing the module. Pretest - This measures your prior knowledge about the lesson at hand. Recap - This part of the module provides a review of concepts and skills that you already know about a previous lesson. Lesson - This section discusses the topic in the module. Activities - This is a set of activities that you need to perform. Wrap-Up - This section summarizes the concepts and application of the lesson. Valuing - This part integrates a desirable moral value in the lesson. Posttest – This measures how much you have learned from the entire module. EXPECTATION This lesson aims to help you Apply the principles of conservation of mass to chemical reactions. Furthermore, you are expected to: 1. state the Law of Conservation of Mass; 2. explain the "Law of Conservation of Mass" by using common chemical reactions around us; 3. balance given chemical equations; and 4. appreciate the Law of Mass Conservation in the balance of nature. PRE–TEST Directions: Read each statement carefully. Encircle the letter of the correct answer. 1. The law of conservation of mass states that matter is neither created nor _______. a. rearranged b. destroyed c. transferred d. changed 2. In a closed system, a chemical reaction takes place. The mass of the reactants in the beginning of the reaction is 25g. At the end of the reaction, what must the mass be to follow the law of conservation of mass? a. 25 grams b. 30 grams c. 40 grams d. 50grams 3. How is a chemical equation balanced? a. changing subscripts b. erasing elements as necessary 4. When the equation, Fe + Cl2 coefficient for Cl2? a. 1 b. 2 c. adding coefficients d. adding elements as necessary FeCl3 is c. 3 balanced, what d. 4 5. What are the missing coefficients for the skeleton equation below? NH3 + O2 N 2 + H2 O a. 4,3,2,6 c. 1,3,1,3 b. 2,1,2,3 d. 2,3,2,3 is the RECAP In your previous lesson, you have learned about chemical changes that matter undergoes and the evidence of such chemical change. Directions: Determine the evidence manifested by the following chemical changes by matching column A with column B. 1. 2. 3. 4. 5. COLUMN A Burning of wood Curdling of milk Ripening of fruit Starch added to vinegar Tarnishing of silverware a. b. c. d. COLUMN B formation of precipitate evolution of heat and light change in intensive properties formation of gas L E S S ON From the time we get up in the morning to the time that we sleep at night, chemical changes are taking place, within us and outside of us. Plants grow through photosynthesis, foods that we eat are digested by the body, metals corrode, raw materials are being converted to useful products, new medicines are being developed, more versatile and cost-effective materials are being made. Various chemical changes that occur around us have significant effect to our environment and consequently to our health. Chemical changes occurring in industries result to products that are useful to us. The wastes we throw continue to undergo chemical changes and this has an impact on our well-being as well. The irresponsible use of fertilizers, herbicides and pesticides have negatively affected plants and aquatic life. We continue to pollute the atmosphere with vehicle and industrial gas emissions. The Law of Conservation of Mass Imagine you enter a closed system, a room that is perfectly sealed where nothing can enter the room, and nothing can escape. In this closed system, you light a candle and let it burn, watching as some of the wax seems to disappear as the flame travels down the wick. Where does the wax go? Is it truly disappearing? The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction. If we account for all reactants and products in a chemical reaction, the total mass will be the same at any point in time in any closed system. The law of conservation of mass states that in a closed system, the mass of the system cannot change over time. Look at our example of the candle in the closed room. Though much of the wax itself is no longer present in its original form, all the mass of the wax is still present in the room, albeit in a different form. When the flame was lit, oxygen gas from the room reacted with the candle wax to produce water vapor and carbon dioxide gas. If you massed the reactants oxygen and wax, it would equal the mass of the products water and carbon dioxide. We can remember the law of conservation of mass with this simple statement: The mass of the reactants must equal the mass of the products. Sadly, for fans of magic, anything that has mass, including matter and energy, cannot be created or destroyed. That means, mass cannot simply appear out of nowhere and equally it cannot disappear. Matter may change forms however, giving the illusion of nothing out of something or vice versa, but the mass of the matter is always the same before and after the change. If 22 grams of reactants go into a chemical reaction, then 22 grams of products must be produced. The Law of Conservation of Mass holds true because naturally occurring elements are very stable at the conditions found on the surface of the Earth. Most elements come from fusion reactions found only in stars or supernovae. Therefore, in the everyday world of Earth, from the peak of the highest mountain to the depths of the deepest ocean, atoms are not converted to other elements during chemical reactions. Because of this, individual atoms that make up living and nonliving matter are very old and each atom has a history. An individual atom of a biologically important element, such as carbon, may have spent 65 million years buried as coal before being burned in a power plant, followed by two decades in Earth's atmosphere before being dissolved in the ocean, and then taken up by an algal cell that was consumed by a copepod before being respired and again entering Earth's atmosphere. The atom itself is neither created nor destroyed but cycles among chemical compounds. Ecologists can apply the law of conservation of mass to the analysis of elemental cycles by conducting a mass balance. These analyses are as important to the progress of ecology as Lavoisier's findings were to chemistry. Figure 1. Mass Experiments and Simple Reacting Mass Calculations https://docbrown.info/page04/4_73calcs03com.htm Writing and Balancing Chemical Equation When atoms gain or lose electrons to yield ions, or combine with other atoms to form molecules, their symbols are modified or combined to generate chemical formulas that appropriately represent these species. Extending this symbolism to represent both the identities and the relative quantities of substances undergoing a chemical (or physical) change involves writing and balancing a chemical equation. Consider as an example the reaction between one methane molecule (CH 4) and two diatomic oxygen molecules (O2) to produce one carbon dioxide molecule (CO 2) and two water molecules (H2O). The chemical equation representing this process is provided in the upper half of Figure 1, with space-filling molecular models shown in the lower half of the figure. Figure 2. The reaction between methane and oxygen to yield carbon dioxide in water (shown at bottom) may be represented by a chemical equation using formulas (top). https://s3-us-west2.amazonaws.com/coursesimages/wp.jpeg This example illustrates the fundamental aspects of any chemical equation: • The substances undergoing reaction are called reactants, and their formulas are placed on the left side of the equation. • The substances generated by the reaction are called products, and their formulas are placed on the right sight of the equation. • Plus signs (+) separate individual reactant and product formulas, and an arrow (→) separates the reactant and product (left and right) sides of the equation. • The relative numbers of reactant and product species are represented by coefficients (numbers placed immediately to the left of each formula). A coefficient of 1 is typically omitted. Balancing Equations A balanced chemical is equation has equal numbers of atoms for each element involved in the reaction are represented on the reactant and product sides. This is a requirement the equation must satisfy to be consistent with the law of conservation of matter. It may be confirmed by simply summing the numbers of atoms on either side of the arrow and comparing these sums to ensure they are equal. Note that the number of atoms for a given element is calculated by multiplying the coefficient of any formula containing that element by the element’s subscript in the formula. If an element appears in more than one formula on a given side of the equation, the number of atoms represented in each must be computed and then added together. ACTIVITIES Let’s check your understanding, by performing the three sets of activities. Activity 1: Conservation of Mass Directions: Examine the data for each of the following combustion experiments and answer the questions based on analysis of the data. Experiment #1 REACTANT(S) Magnesium + Oxygen 48.6 g + 32.0 g a. b. c. d. PRODUCT(S) Magnesium Oxide 80.6 g ------> ------> What is the mass of each reactant? ____________________________________ What is the mass of the product? _______________________________________ What is the total mass of reactants? ___________________________________ Does this experimental data support the Law of Conservation of Mass? Explain. ________________________________________________________________________ ________________________________________________________________________ Experiment #2 REACTANT(S) Magnesium + Oxygen ?g + 16.0 g ------> ------> PRODUCT(S) Magnesium Oxide 40.3 g Based on the Law of Conservation of Mass, predict the minimum amount of magnesium that will react with all 16.0 grams of oxygen to produce 40.3 grams of magnesium oxide. Answer: ____________________________ Experiment #3 REACTANT(S) PRODUCT(S) Magnesium + Oxygen ------> Magnesium Oxide 12.2 g + 8.0 g ------> ?g Assuming that magnesium and oxygen will react completely with one another, predict the mass of magnesium oxide that will be produced. Answer: ______________ Experiment #4 REACTANT(S) Magnesium + Oxygen 48.6 g + 50.0 g ------> -----> PRODUCT(S) Magnesium Oxide + Oxygen 80.6 g + ? Predict the mass of oxygen that will be left over after the reaction of 48.6 grams of magnesium with 50.0 grams of oxygen. Answer: ____________________________ Activity 2: Balancing Act Directions: Determine which among the following chemical equations are correctly balanced. Put a (✓) on items with balanced equation and mark (x) for chemical equations that are nor balanced. _________ _________ _________ _________ _________ 1. 2. 3. 4. 5. C4H10O + 6 O2 C7H16 + 11O2 4H2SiCl2 + 4 H2O C7H9 + 3HNO3 C5H8O2 + 2NaH + 2HCl 4CO2 + 5H2O 7CO2 + 8H2O 3H8Si4O4 + 8HCl C7H6(NO2)3 + 3H2O C5H12O2 + 2 NaCl Activity 3: Balancing Chemical Equations Directions: Balance each of the following equation by supplying the appropriate coefficient on the space provided. 1. _____ Fe + _____ Cl2 _____FeCl3 2. _____ Fe + _____O2 _____Fe2O3 3. _____ FeBr3 + _____ H2SO4 Fe2(SO4)3 + _____HBr 4. _____ C4H6O3 + H2O _____C2H4O2 5. _____ C2H4 + _____ O2 _____ CO2 + _____ H2O WRAP–UP To summarize what you have learned today, let’s answer these. Complete the statements by filling up the blank. 1. The law of Mass Conservation states that the mass of the __________ must equal to the mass of the ____________. 2. The substances undergoing reaction are called ____________, and their formulas are placed on the left side of the equation. 3. The substances generated by the reaction are called_________, and their formulas are placed on the right sight of the equation. 4. ________ signs separate individual reactant and product formulas, and an ________ separates the reactant and product (left and right) sides of the equation. 5. To balance a chemical equation, place an appropriate ___________ before each symbol or formula. VALUING Life involves obtaining, utilizing, and disposing of elements. The biomolecules that are the building blocks of life (proteins, lipids, carbohydrates, and nucleic acids) are composed of a relatively small subset of the hundred or so naturally occurring elements. Living organisms are primarily made of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. And each of these important element cycle through the Earth system. Ecosystems can be thought of as a battleground for these elements, in which species that are more efficient competitors can often exclude inferior competitors. Though most ecosystems contain so many individual reactions, it would be impossible to identify them all, each of these reactions must obey the Law of Conservation of Mass — the entire ecosystem must also follow this same constraint. Though no real ecosystem is a truly closed system, we use the same conservation law by accounting for all inputs and all outputs. Scientists conceptualize ecosystems as a set of compartments that are connected by flows of material and energy. Any compartment could represent a biotic or abiotic component: a fish, a school of fish, a forest, or a pool of carbon. Because of mass balance, over time the amount of any element in any one of these compartments could hold steady (if inputs = outputs), increase (if inputs > outputs), or decrease (if inputs < outputs). For example, early successional forests gain biomass as trees grow and thus act as a carbon sink. In mature forests, the amount of carbon taken up through photosynthesis may equal the amount of carbon respired by the forest ecosystem, so there is no net change in stored carbon over time. When a forest is cut (and especially if trees are burned to clear land for agriculture), this stored carbon reenters the atmosphere as CO2. Mass balance ensures that the carbon formerly locked up in biomass must go somewhere; it must reenter some other compartment of some ecosystem. Mass balance properties can be applied over many scales of organization, including the individual organism, the watershed, or even a whole city. POST TEST Let’s measure how much you have learned from this module. Directions: Read each statement carefully. Encircle the letter of the correct answer. 1. There are two reactants in a chemical equation, and one product. The mass of the product is 30g. The mass of the first reactant is 17g. What must the mass of the second reactant be, if the equation is to follow the law of conservation of mass? a. 10 grams b. 11 grams c. 12 grams d. 13 grams 2. How is a chemical equation balanced? a. changing subscripts c. adding coefficients b. erasing elements as necessary d. adding elements as necessary 3. Which of the following is true for a balanced chemical equation? a. The number of various atoms is equal in both sides b. The number of various atoms is more in left side ACTIVITY #3 Balancing Chemical Equations 2 Fe2O3 2. 4 Fe + 3 O2 2 FeCl3 1. 2 Fe + 3 Cl2 3. 2 FeBr3 + 3 H2SO4 4. C4H6O3 + H2O 5. C2H4 + 3 O2 Fe2(SO4)3 + 6 HBr 2 C2H4O2 2 CO2 + 2 H2O ACTIVITY #1 Mass Conservation Expt#1 ACTIVITY #2 Balancing Act 1. 2. 3. 4. 5. ✓ ✓ X ✓ ✓ a. b. c. d. 48.6 g and 32.0 g 80.6 g 80.6 g Yes, because the mass of the reactant and product are the same. Expt #2 WRAP UP Reactant, product Reactant Product Plus, arrow coefficient POSTTEST 1. D 2. C 3. A 4. D 5. A 24.3 g 18.0 g Expt #4 20.2 g Expt #3 1. 2. 3. 4. 5. RECAP B A C D C TO 1. 2. 3. 4. 5. PRETEST 1. B 2. A 3. C 4. C 5. A KEY CORRECTION c. The number of various atoms is more in right side d. Both b & c 4. What is the coefficient of CO2 when the following equation is properly balanced with the smallest set of whole numbers? C4H10 + O2 ---> CO2 + H2O a. 1 b. 4 c. 6 d. 8 5. Which of the following is the correct balanced reaction? a. 2C3H8 + 10O2 → 6CO2 + 8H2O b. C3H8 + O2 → CO2 + H2O c. C3H8 + O2 → 3CO2 + 2H2O d. C3H8 + 4O2 → 3CO2 + 4H2O R E F E R E N CE S Textbooks • • Science Grade 10. Learner’s Manual. “Chemical Reactions”. Philippines: Department of Education, May,2012. Malone & Dolter. Basic Concepts of Chemistry. John Wiley & Sons, Inc. 2010. Websites • https://Courses/can/intro/03%3A_Matter_and_Energy/3.07%3A_Conserva tion_of_Mass__There_is_No_New_Matter#:~:text=The%20law%20of%20conservation%20of %20mass%20states%20that%20matter%20cannot,oxygen%20when%20it%2 0first%20reacted. Accessed April 18, 2021. • https://study.com/academy/lesson/the-law-of-conservation-of-massdefinition-equation-examples.html Accessed April 26, 2021. • https://courses.lumenlearning.com/atd-sanjacintroductorychemistry/chapter/writing-and-balancing-chemical-equations2/#:~:text=An%20equation%20is%20balanced%20when,law%20of%20conse rvation%20of%20matter. Accessed: April 26, 2021.
