General Chemistry 1 Module 5 PDF

SHS General Chemistry 1 Quarter 2 – Week 5 Module 5 - Polarity of Simple Molecules General Chemistry 1 Grade 11/12 Quarter 2 - Module 5 - Polarity of Simple Molecules First Edition, 2020 Copyright © 2020 La Union Schools Division Region I All rights reserved. No part of this module may be re...

SHS General Chemistry 1 Quarter 2 – Week 5 Module 5 - Polarity of Simple Molecules General Chemistry 1 Grade 11/12 Quarter 2 - Module 5 - Polarity of Simple Molecules First Edition, 2020 Copyright © 2020 La Union Schools Division Region I All rights reserved. No part of this module may be reproduced in any form without written permission from the copyright owners. Development Team of the Module Author: FEMY B. NUESCA, MT-II Editor: SDO La Union, Learning Resource Quality Assurance Team Illustrator: Ernesto F. Ramos Jr., P II Management Team: Atty. Donato D. Balderas, Jr. Schools Division Superintendent Vivian Luz S. Pagatpatan, PhD Assistant Schools Division Superintendent German E. Flora, PhD, CID Chief Virgilio C. Boado, PhD, EPS in Charge of LRMS Rominel S. Sobremonte, Ed.D., EPS in Charge of Science Michael Jason D. Morales, PDO II Claire P. Toluyen, Librarian II General Chemistry 1 Quarter 2 – Week 5 Module 5 - Polarity of Simple Molecules  TARGET “Like begets like”. The polarity of the molecule is a concept that could unravel answers for us to have a better understanding about the reactivity of molecules We can use the concept of polarity to predict whether two compounds are miscible which means compounds can be mixed to form a solution. Polar solvents could dissolve polar molecules. This explains why alcohol and water are completely miscible (both are polar) and why oil and water don’t mix (nonpolar and polar). In this module, learnt- well topics on Lewis structure, molecular geometry as well as about electronegativity will give you good bases in grasping concepts in determining the polarity of simple molecules. After going through this module, you are expected to: 1. Determine the bond polarity using difference in electronegativities of molecules 2. Determine the polarity of molecule 3. Determine the direction of a molecule’s polarity  JUMPSTART Polarity Defined To start with let us define polarity. Polarity is a state or a condition of an atom or a molecule having positive and also negative charges. We know that molecules are neutral. If the negative charge is evenly distributed around a molecule then it is not polar. However, if the negative charge is not evenly distributed then it is polar. How do we determine if the charges are evenly or not evenly distributed around a molecule? Follow the following concept on electronegativity. Electronegativity Defined Electronegativity is the tendency of an atom to attract electrons to itself. The greater the electronegativity value, the greater the tendency of an atom to attract more electrons, the more electronegative the element and this is symbolized with the Greek symbol δ-. The lower the electronegativity value the element it is less negative δ+. Thus, there is an unequal attraction of electrons toward atoms which made up the molecule. Study the table below. Table1: Type of bond vs. Difference in Electronegativity Type of Bond Difference in electronegativity (ΔEN) Non Polar /Pure 1.7 Note: The values may differ from other references, but most textbooks use the indicated values.  For you to understand the lesson on type of bonds, complete the table below. The first one is done for you. Use your Periodic Table and place your answers in another sheet of paper. Bond Difference in electronegativity Type of Bond (ΔEN) ( ionic, polar, nonpolar ) Ca-O Ca = 1.0; O = 3.44 ΔEN 2.44 ionic N-I P-Br Cl-Cl N-Cl The type of bond formed will give us an idea to the polarity of bond meaning that even the type of bond formed is polar will not always be a polar molecule. DISCOVER From the previous module you were tasked to do the Lewis Structure which describes the bonding of molecules and polyatomic ions. If the electrons are shared it is covalent bond. If the electrons are not shared but there is a transfer of electrons, that is, gain or loss of electrons, the bond that is formed is ionic bond. In polar covalent bonds the electrons are not equally shared by the bonding atoms. Thus, there is a shifting in electron density towards the more electronegative atom. Which is symbolized by a crossed arrow pointing towards the direction of the shift that is, to the more electronegative atom. Polar molecules have a partial negative charge δ- on one atom which is more electronegative while having a partial positive charge δ+ on the less electronegative atom. The impartiality of the polar molecules exhibit dipole moments. In the presence of an electric field, the positive end of the molecules orients themselves towards the negative plate. Nonpolar molecules have no dipole moments.  Study the table below showing the difference between bond polarity. Table 2: Polar vs. Non Polar Bonds Type of Bond Type of Example Molecular Manner of atom Orbital sharing of electrons (Lewis Structure ) Polar Bond different P-Br;C-O asymmetrical Unequal NonPolar Same Cl-Cl :Cl2, symmetrical Equal Bond H2, F2 Yes! You are Correct in your observation…Polar bond is formed if the atoms or elements are different, the molecular shape is asymmetrical*** better Recall from previous lesson*** and unequal sharing of its electrons. Further explained that the molecular orbital is symmetrical with respect to both atomic nuclei of the atom and asymmetrical if there if greater electron density near one end of the atomic nuclei involved in the molecular orbital. Now let us further look into other considerations to make molecules be polar. Dipole Moment Further Defined The dipole moment can be defined as the product of the charge and the distance between the charges. To maintain neutrality, the charges on the ends of the molecule must be equal in magnitude but opposite in sign. However, if it is not there will be partial negative, δ- and partial positive. δ-. This means we will apply vector addition. ABREAST YOURSELF: Here comes the meat of the lesson… Example # 1 Water (H2O) a) Bond Type: H has electronegativity value of 2.20 and O has an electronegativity value of 3.44. The ΔEN is equal to 1.24 , so the bond type is polar as based from table 1 b) shifting of the electron density or the direction of molecule’s polarity Dipole-indicates the magnitude and direction of molecule’s polarity, pointing to the negative side of the molecule The EN value of O ( 3.44)is greater than H (2.2), so the shifting will be towards O To emphasize, a polar molecule has To uneven distribution emphasize, of charge, a polar molecule hasmaking uneven one side more positive, δ+, the other side more negative, δ-. distribution of charge, making one side Using the symbol, H O moreb positive, δ+, the other side more negative, δ- c)Geometric shape is bent. It is asymmetrical meaning it does not have a symmetrical shape. Defining again symmetry that the outside atoms are evenly distributed around the central atom. The central atom here is O, and both H are found on both side of the O which makes it non-symmetrical. Using vector addition: +x -x Y axis there is a net value moving same direction +y +y X axis the dipole moments are cancelled. No net value Therefore, H2O is polar Example #2 Carbon dioxide, CO2 a) Bond type EN of O = 3.44 EN of C = 2.55 Δ EN= 0.89 (polar bond) b) shifting of the electron density or the direction of molecule’s polarity Oxygen is more electronegative, shifting towards O Look at the arrows Toward left (+ X) and toward right ( - X ) Using vector addition, it totally cancels each other. The dipole moments are equal in magnitude but in opposite direction and arranges symmetrically about the central atom in a linear geometry. So the dipole moments are cancelled. Therefore, CO2 is not a polar molecule Let us remember …. The bond dipole moments will cancel if: 1) They are of the same magnitude 2) They are symmetrically arranged about the central atom To distinguish between polar bonds versus polar molecules. Some molecules have polar bonds but are not polar. The molecular geometry determines whether the molecule is polar or not. Here are some hints to make easy in determining polarity of molecules 1. If there is one set of molecules like H2, H2, F2 it is a non polar molecule. The ΔEN is equal to zero 2. For any hydrocarbons molecule like Methane (CH4 ), Propane, Butane it is nonpolar , the molecular geometry is linear. The dipole moments are cancelled. 3. For different elements. Draw the Lewis Structure and determine the dipole moment, if there is a net value then it is a polar molecule.  EXPLORE The following practice problems are prepared for you to polish and enrich your understanding in determining the polarity of molecules. Copy and complete the table below in another sheet. Good Luck and Have Fun! Activity 1 Molecule ΔEN Type of Bond Diagram ( Show Molecular partial charges and Geometry dipole moments if applicable ) 1. CF4 2. H2 3. SO2  DEEPEN Let as further apply the Polarity of molecules. Let us take a look at problems below. Do what is /are required at by the problems 1. Show the Lewis Structure and geometric sketch for HCN. The electronegativities of H, C, and N are 2.20, 2.55, and 3.04. Is the molecule Polar? Support your answer. Note that molecules with one polar bond are always polar. Even if the other is not polar 2. Decide whether the OF2 is polar molecule. The electronegativities of oxygen and fluorine,3.44 and 3.98 respectively. Support to your answer. 3. The molecular geometry of CCl4 is tetrahedral. Is it a polar molecule? Support your answer To sum up further, A polar molecule has a dipole, where part of the molecule has a partial positive charge and part has a partial negative charge. A polar molecule has an asymmetric shape, lone electron pair, or central atom bonded to other atoms with different electronegativity values. Polar molecules are often hydrophilic and soluble in polar solvents. Polar molecules often have higher melting points than nonpolar molecules with similar molar masses  GAUGE I. COMPLETION TYPE. Complete what is required at by the following table. Copy table in a separate sheet. Bond Central ΔEN Type of Bond Polar Molecule or Atom Nonpolar Molecule 1. Sulfur difluoride SF2 2. Methane CH4 3. Oxygen O2 4. Ammonia NH3 5. Hydrogen sulfide H2 S II. Predict the molecular polarity of this molecule. Support your answer. (10 pts) Rubrics: 5 4 3 2 Prediction Prediction is Prediction is Prediction is No prediction clearly stated somewhat unclear unclear Rationale All points are Most points Some points No point is given are given are given given Key Answer References: A. Books Reyes, Armida B.( 2019). General Inorganic and Organic Chemistry:Laboratory Manual for Health –related Programs. Dagupan, Philippines: SLA Publishing House Ilao , Lucian V.et.al.(2016).General Chemistry 1.Manila, Philippines :Rex Bookstore, Inc. Commission on Higher Education.(2015). K to 12 Transition Program Management Unit -Senior High School Support Team. Teaching Guide for Senior High School-General Chemistry 1.Quezon City, Philippines. B. Online and Electronic Sources: “Polarity of Molecules”. Accessed October 27,2020.https://byjus.com/chemistry/polarity/ “How to determine if Molecule is Polar or Nonpolar?’https://www.youtube.com/watch?v=v1Kp3yEIWC0 “Introductory Chemistry”.Accessed October 24,2020. https://courses.lumenlearning.com/suny-mcc-introductorychemistry/ Polar Molecules Tutorial: How to determine polarity in a molecule: https://www.youtube.com/watch?v=72CQe-_PJU4&t=29s “ Types of Bonds “. Accessed October 27,2020.https://chemistrybytes.com/welcome/concepts/bonding- 101/types-of-bonds-ionic-and-covalent/ Anne Helmenstine.”Polar and Nonpolar Molecules”. Accessed October 27,2020. https://sciencenotes.org/polar-and-nonpolar-molecules/ “Polarity and Electronegativity Worksheet”.Accessed October 23,2020.https://3u_polarity_and_electronegativity_ws_answers.pdf