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Physical Science

Quarter 1 – Module 4:

Polarity of Molecules and Its

Properties

Personal Development Alternative Delivery Mode Quarter 1 – Module 4: Polarity of Molecules and Its Properties 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 Secretary: Leonor Magtolis Briones Undersecretary: Diosdado M. San Antonio Printed in the Philippines by ________________________ Department of Education – RegionIV-A CALABARZON Office Address: Gate 2 Karangalan Village, Barangay 1900, Cainta, Rizal 1800 Telefax: 02 - 8682 - 5773/8684-4914/8647- 7487 E-mail Address:[email protected]/[email protected] Development Team of the Module Writers: Bayani T. Vicencio, Valeria Amor C. Rosita Editors: Priscilla D. Domino Gertrudes L. Malabanan Reviewers: Rogelio D. Canuel, Elmer C. Bobis, Gertrudes L. Malabanan Illustrator: Geselle A. Teaňo Layout Artist: Elsie R. Reyes Management Team: Wilfredo E. Cabral Job S. Zape Jr. Eugenio S. Adrao Elaine T. Balaogan Helen A. Ramos Rhina O. Ilagan Edna U. Mendoza Ronaldo V. Ramilo

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Introductory Message

For the facilitator: Welcome to the Physical Science 11/12Alternative Delivery Mode (ADM) Module on Polarity of Molecules and Its Properties! This module was collaboratively designed, developed and reviewed by educators both from public and private institutions to assist you, the teacher or facilitator in helping the learners meet the standards set by the K to 12 Curriculum while overcoming their personal, social, and economic constraints in schooling. This learning resource hopes to engage the learners into guided and independent learning activities at their own pace and time. Furthermore, this also aims to help learners acquire the needed 21st century skills 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: 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. Furthermore, you are expected to encourage and assist the learners as they do the tasks included in the module. Notes to the Teacher This contains helpful tips or strategies that will help you in guiding the learners.

iii For the learner: Welcome to the Physical Science 11/12 Alternative Delivery Mode (ADM) Module on Properties of Molecules based on its Polarity! The hand is one of the most symbolic parts of the human body. It is often used to depict skill, action and purpose. Through our hands we may learn, create and accomplish. Hence, the hand in this learning resource signifies that you as a learner is capable and empowered to successfully achieve the relevant competencies and skills at your own pace and time. Your academic success lies in your own hands! 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 resource while being an active learner. This module has the following parts and corresponding icons: What I Need to Know This will give you an idea of the skills or competencies you are expected to learn in the module. What I Know This part includes an activity that aims to check what you already know about the lesson to take. If you get all the answers correctly (100%), you may decide to skip this module. What’s In This is a brief drill or review to help you link the current lesson with the previous one. What’s New In this portion, the new lesson will be introduced to you in various ways such as a story, a song, a poem, a problem opener, an activity or a situation. What is It This section provides a brief discussion of the lesson. This aims to help you discover and understand new concepts and skills. What’s More This comprises activities for independent practice to solidify your understanding and skills of the topic. You may check the answers to the exercises using the Answer Key at the end of the module. What I Have Learned This includes questions or blank sentence/paragraph to be filled in to process what you learned from the lesson. What I Can Do This section provides an activity which will help you transfer your new knowledge or skill into real life situations or concerns.

What I Need to Know

This module was designed and written with you in mind. It is here to help you master the concept of polarity of molecules. The scope of this module permits it to be used in different learning situations. The language used recognizes the varied vocabulary level of students. The lessons are arranged to follow the standard sequence of the course. But the order in which you read them can be changed to correspond with the textbook you are now using. The module is divided into three lessons, namely: ● Lesson 1 – Properties of Molecules based on its Polarity After going through this module, you are expected to:

1. define solubility, miscibility and polarity;

2. identify the different types of intermolecular forces of attraction;

3. explain how polarity of molecules related to its properties

What I Know

Choose the letter of the best answer. Write the chosen letter on a separate sheet of paper.

1. Which of the following is TRUE of polar molecules? i. Have high boiling point iii. low surface tension ii. Have high melting point iv. High vapor pressure a. I only b. I and II only c. II and III only d. IV only
2. Which of the following intermolecular forces of attraction (IMFA) is arranged from strongest to weakest? a. H- bonding – dipole-dipole – London forces b. London-forces – dipole-dipole – H-bonding c. Dipole-dipole – London forces – H- bonding d. H-bonding – London forces – dipole-dipole For numbers 3-6, consider the choices below: a. boiling point c. Viscosity b. solubility d. vapor pressure
3. Refers to the resistance of a liquid to flow.
4. Is temperature at which the liquid starts to boil.
5. Defined as the pressure exerted by a substance when in its gaseous state.
6. The ability of a substance to be dissolved in another substance to form a solution.
7. The following are examples of viscous substances EXCEPT: a. blood c. vinegar

b. honey d. syrup

Lesson

Properties of Molecules

based on its Polarity

From the previous module, you learned how to determine the polarity of bonds using the concept of electronegativity. Also, you learned that polarity of molecules is affected by both the polarity of bonds and its molecular shape or geometry.

What’s In

Let us have some warm up exercise for our nerve cells before we proceed to the presentation of our lesson. You will perform a simple activity that will help you recall some basic concepts related to polarity of molecules. Have some fun!

Notes to the Teacher

There are numerous terms or concepts being studied in science and most of them are either difficult to spell out or pronounce. As teachers, we should think of engaging activities that would motivate our students to learn and at the same time increase their vocabulary skills and spelling ability. Below is an example of an activity you could employ in your class.

O N L E A P I R

L E C M O U L E

O P A L R O D N B

L E C M O U L E

N A R O P O L N B D O N

A C E G T R O T L I Y E I T E N V

M A T O

RIDDLE: It shows the three-dimensional arrangement of bonding groups of atoms around a central atom. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Can you define the following words/terms that you have decoded?

WORD CRYPTOGRAM

Directions: Unscramble the letters by placing the correct letter sequence in the shaded boxes to come up with the correct answer for each number. Use the numbered boxes to complete the answer to the riddle below.

What is It

A. Polarity, Solubility, and Miscibility

One of the practical applications of polarity of molecule in real-life scenario is manifested on the solubility and miscibility of substances to form solution. Solubility is defined as the ability of a solid substance to be dissolved in a given amount of solvent while miscibility is the ability of the two liquids to combine or mix in all proportions, creating a homogenous mixture. The general rule to remember about the solubility and miscibility of molecular compounds can be summarized in a phrase, “ like dissolves like ” or “like mixes with like”. This means that polar substances will only be dissolved or mixed with polar substances while nonpolar substances will be soluble or miscible with another nonpolar substance. Now I want you to try the exercises below in order to assess how much you have understood the solubility (and miscibility) rule of substances in relation to their polarity. Which of the following substances below will most likely mix with each other? a. water (H 2 O) and chloroform (CHCl 3 ) b. benzene (C 6 H 6 ) and chloroform (CHCl 3 ) c. water (H 2 O) and vinegar (CH 3 COOH) d. acetone (C 3 H 6 O) and toluene (C 6 H 5 CH 3 ) e. carbon tetrachloride (CCl 4 ) and water (H 2 O) What chemistry concept did you used in answering the question above? If you answered polarity of molecules, then you are on the right track. Great job! Benzene and chloroform are both nonpolar compounds while water and vinegar are both polar compounds, thus they are miscible to each other. However, the rest is a combination of polar and nonpolar molecules and therefore will not mix and instead will form two layers even if shaken or carefully stirred. B. Bond Strength and Physical Properties of Covalent Compounds From the previous module, you learned the intramolecular forces of attraction , the attractive force that binds atoms together. In this module, you will learn another type of attractive force, the intermolecular forces of attraction (IMFA) which exists between molecules.

In this lesson, we will not discuss IMFA in so much detail because it will be tackled to you in the next module. We will just focus on the following salient points of IMFA and its effect on the physical properties of covalent compounds:

1. There are several types of IMFA and below they are arranged from STRONGEST to WEAKEST.

Ion-dipole → H-bonding→ dipole-dipole→dipole-induced dipole→

London forces of attraction

2. The strength of IMFA greatly affects the physical properties of substances

such as boiling point, melting point, vapor pressure, surface tension, etc. Before we move further, try to perform the exercise below to test your ability to analyze concepts and principles that you have learned from the discussion. Put a check (/) to those properties applicable for polar molecule. ____1. High boiling point ____7. High vapor pressure ____2. Low boiling point ____8. Low vapor pressure ____3. High melting point ____9. High surface tension ____4. Low melting point ____10. Low surface tension ____5. High volatility ____11. H-bonding & dipole-dipole present ____6. Low volatility ____12. London dispersion is present How well did you perform in this exercise? Continue reading for you to find out the correct answers for this activity. From the above discussion you learned that there are several types of IMFA and their relative strength as compared to other types. Strong intermolecular forces tend to yield solids and liquids while weak intermolecular forces favor formation of gases. Table 1 shows the comparison of the various types of IMFA while table 2 shows the physical properties of polar and nonpolar molecules as affected by the type of IMFA present. Table 1. Summary of Types of Intermolecular Forces of Attraction (IMFA) Type of IMFA Interacting Substances Examples Ion-dipole Ion (cation or anion) and a polar molecule NaCl dissolved in H 2 O; Ca^2 + and PCl 3 Hydrogen bonding Polar molecules containing H chemically bonded to a small and highly electronegative nonmetal atom such as N, O, and F

H 2 O, NH 3 , CH 3 OH

Dipole – dipole Polar molecules CH 3 F and H 2 S; HCl; Dipole-induced dipole Polar and nonpolar molecules HI and CH 4 London forces All substances and solely for nonpolar molecules and noble gases O 2 , N 2 , He gas, Br 2

What’s More

Activity 1. Strength of IMFA and Physical Properties of Covalent Compounds For each pair of molecules, identify the one with the higher boiling point (BP), melting point (MP), viscosity (V), surface tension (ST) and vapor pressure (VP). Briefly explain your choice. BP MP V ST VP Methane, CH 4 carbon tetrachloride, CCl 4 Dihydrogen sulfide, H 2 S water, H 2 O Methanol, CH 3 OH ethanol, CH 3 CH 2 OH Acetic acid, CH 3 COOH acetone, CH 3 OCH 3 Adapted from Punzalan and Monserat (2016)

What I Have Learned

1. Distinguish intramolecular forces of attraction and intermolecular forces of attraction.
2. In your own words, explain the Solubility Rule.
3. Compare and contrast polar and non-polar molecules based on its physical properties.
4. What relationship can you derive between the strength of IMFA and the physical properties of covalent molecules?

What I Can Do

A. Using the concept of bond polarity and solubility, explain why water (H 2 O) and vinegar are miscible, but vinegar and oil are immiscible. B. Using the concept of intermolecular forces of attraction, explain why butter melts at room temperature but solidifies when refrigerated. C. Explain the importance polarity of molecules to biological processes such as in the structure of proteins and phospholipids.

7. Which of the following substances is miscible in hexane (C 6 H 14 )? a. Acetone (C 3 H 6 O) b. Vinegar (CH 3 COOH) c. Chloroform (CHCl 3 ) d. Methanol (CH 3 OH)
8. The following are intermolecular forces of attraction EXCEPT: a. H-bond b. Dipole-dipole c. Covalent bond d. London forces
9. Which of the following properties has indirect relationship with the strength of IMFA? a. Boiling point b. Melting point c. Surface tension d. Vapor pressure
10. In which of the following solvents would molecular iodine (I 2 ) be most soluble? a. Vinegar b. Water c. Ethyl alcohol d. Carbon tetrachloride True or False: Write T if the statement is true, otherwise write F.
11. H-bonds are broken when ice melts.
12. Molecules with H-bonds have higher boiling point than molecules with dipole- dipole bond.
13. In covalent molecules, vapor pressure decreases with decreasing strength of intermolecular forces.
14. When the attractive forces holding particles together are greater, you have to get to a higher temperature to break those forces, so the melting point is higher.
15. The strength of dispersion (London) forces tends to increase with increased molecular weight.

Additional Activities

1. Briefly explain why water is considered as the universal solvent.

2. Using the concept of IMFA, account for the difference in boiling point and melting point of the following molecular substances: Substance Boiling point (^0 C) Melting point (^0 C) Helium gas, He - 269 - 272 Methane, CH 4 - 162 - 184 H 2 O 100 0 Ethanol, C 2 H 5 OH 78 - 117