^ -0 Name: Molecule Polarity PhET Lab S'.-. Related to Objective 5 : A study of electronegativity, bond polarity, and molecular polarity. \-cr\denoA of An A4-O $V\ *fo A.HvA £-f e ~ vv \"< " V.V/A '. * i Introduction: i i In this atomic-level simulation, you will investigate how atoms' electronegativity value affects the bonds they produce. When two atoms bond, a pair of electrons is ii Molecule Polarity shared between atoms. Electronegativity is a measure of a single atom' s ability to hoard electrons shared in that bond, in this lab you will work diligently, at your own pace, to answer a number of questions. To begin, from what you ' ve already learned about the protons and electrons in an atom, what would cause an atom to have a high electronegativity value ? av\ rvfnt/iA Ha.s vyvnri \iakv\ce e~ FKJ \fonil , - be UvoUgr NwMidM View y) Bond Dipole Why might an atom have a low electronegativity value ? Zi Partial Charges vj Bond Character a ev Atoms Procedure: i Two Surface \j none Electrostatic Potential Turn on ( check ) all view options. Take your time and investigate how the binary compound's bond behaves when the atom ' s electronegativity and orientation are changed. Do not rush through this step. o Electric Field o Describe the bond formed between two atoms with similar, low electronegativities. morf Electron Density off on tpvqfmf Describe the bond formed between two atoms with similar, high electronegativities. fnore CPVMIgyvV Describe the bond formed between two atoms with very different electronegativities. Vnore l o true. Describe (in your own words) what is meant by partial charges, 6- and 6+. e/ 6 - represents: at 6+ represents: Hof fDtfl&VxW /vtedl more jgSS < i \ ~fm4

What would bring about a higher electron density around an atom? \ ) A «»»0( ^ juaP K' * • J PA (W 1 rkiASifu around £ * 15 Less HIAK f'Lc ^ [ /; Partial Charges Electric Field how it interacts with other molecules and its environment. For instance, molecules with high molecular dipoles tend to have high intermolecular forces. (Why? ) » on off BTW: The molecular dipole is found using vector addition, adding the bond dipoles together; think a tug -of-war . Take some time and adjust each of the atom's locations and electronegativity values several times. Observe how the bond dipoles ( between A- B and B-C) add to produce a molecular dipole. How might a molecule with two strong bond dipoles have no molecular dipole at all? pnirt / iouV " wioifcule \s sLjraA .. •: • If .. •'V' J fit ff ; a ^ umehncol How might a molecule have a very strong molecular dipole. large Real Molecules !A/igt4 Iryfc- \ ’ " Like dissolves like" is a way to remember that molecules with similar molecular dipoles will tend to interact favorably and mix. For instance, water ( H20) is a polar molecule. It will mix well ( dissolve ) polar molecules, such as ammonia ( NHa), a mixture often used in household cleaners. Both molecules possess strong molecular dipoles. . A molecule such as methane (CH4 ) would not dissolve well into water Why? jltOftlg. C- O /• ( ncmpolaf ivwlervle) 4 Before using the simulation, complete the table below ( with a V) to predict which or the following should dissolve into water. Create a Lewis-dot diagram (:0=C= 6: ) for each to guide your thinking (use a separate page ) , Prediction ( before using the simulation ) H2 N2 02 F2 HF y / H 2O co2 V HCN V/ - C R FJ2 03 NH3 BH3 BF3 CH2O / 1 ' FJ)CF CH4 ( CH3 F ) CH2F2 ( , CH3 ^ v/ v/ 4 / v CHCI3 x/ «Optionai» Next, use the simulation to determine with of the species should dissolve in water. H2 N2 02 F2 HF H20 C02 HCN 03 NH3 BH3 BF3 CH2O CH4 V Finally, what type of solvent would be required to dissolve nonpolar compounds? CH3 F CH 2F2 CH 3 F CF4 CHCI3