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Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Lesson 1.1 Kinetic Molecular Theory of Matter Contents Introduction 1 Learning Objectives 2 Warm Up...

Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Lesson 1.1 Kinetic Molecular Theory of Matter Contents Introduction 1 Learning Objectives 2 Warm Up 2 Learn about It! 3 Kinetic Molecular Theory of Matter 3 Matter Is Composed of Small Particles 4 Molecules Interact through Attractive Forces 5 Molecules Are in Constant Random Motion 5 Temperature Is a Measure of the Average Kinetic Energy 5 States of Matter 6 Key Points 8 Check Your Understanding 9 Challenge Yourself 10 Bibliography 11 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Lesson 1.1 Kinetic Molecular Theory of Matter Introduction Have you ever bought an ice cream on a hot summer day? If yes, then you must have noticed how ice cream, when taken out of the freezer, takes a definite shape, but when exposed in the summer heat, slowly loses its form and melts. In this lesson, you will be learning about theories governing the different states of matter. You will learn why solids have definite shapes, but liquids and gases take up the shape of their container. You will also learn the relationship of the different macroscopic properties of matter to that of its molecular interactions. 1.1. Kinetic Molecular Theory of Matter 1 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Learning Objectives DepEd Competency In this lesson, you should be able to do the Use the kinetic molecular model to explain properties of liquids and following: solids Explain the kinetic molecular (STEM_GC11IMF-IIIa-c-99). theory of matter. Compare and contrast the different states of matter based on the kinetic molecular theory. Warm Up Shake It Off! 10 minutes Do you still remember the different states of matter? This activity recalls concepts on the properties of the states of matter. Materials round magnets small box paper cup paper bag ping-pong balls Procedure 1. Place the magnets and ping-pong balls into paper cups labeled “A” and “B,” respectively. 2. Observe the overall shape of the contents of each cup. 3. Transfer the contents in separate boxes labeled “A” and “B,” respectively. 4. Observe the overall shape of the contents of each box. 5. Try shaking the boxes. Observe whether the balls or pieces of magnets are able to move around. 1.1. Kinetic Molecular Theory of Matter 2 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Observation Table Table 1.1.1. Observing how the balls (A) and pieces of magnets (B) move in a cup and a box Container Observation for Observation for A B cup box shaking the box Guide Questions 1. What happened to the overall shape of the ping-pong balls in the cup? 2. What happened to the overall shape of the magnets in the cup? 3. What happened to the shape of the ping-pong balls in the box? 4. What happened to the shape of the magnets in the box? 5. How different were the motions of the contents of the ping-pong balls and the magnets? Learn about It! What does the kinetic molecular theory state? Kinetic Molecular Theory of Matter The kinetic molecular theory of matter provides an overview of the microscopic properties of molecules or atoms and their interactions. These concepts, when combined, lead to the macroscopic behavior and properties of matter. The kinetic molecular theory describes the microscopic properties of matter and how they translate to the state and other properties of matter. The kinetic molecular theory states that: 1.1. Kinetic Molecular Theory of Matter 3 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids (1) Matter is composed of small particles. (2) The molecules interact with one another through attractive forces. The strength of these forces is related to the distance between the particles. (3) These molecules are always in constant random motion. (4) The temperature of a substance is a measure of the average kinetic energy of the molecules. Table 1.1.2. Examples of particles comprising matter Examples Gold Oxygen Water Sodium Chloride Macroscopic gold bar oxygen gas in drop of water table salt a tank Microscopic gold atoms oxygen water molecules sodium and molecules chloride ions Matter Is Composed of Small Particles Atoms are the building blocks of matter. Matter can exist as a group of individual atoms or as a group of atoms bonded together called molecules. A pure gold bar, for example, is composed of many gold atoms. However, some elements can exist as molecules. For example, oxygen gas exists as a diatomic molecule, O2. Matter can also come in the form of compounds. Compounds are produced when two or more atoms of different elements combine chemically. Water (H2O) is a compound composed of molecules made up of an oxygen atom covalently bonded to two hydrogen atoms. Sodium chloride is a compound made up of sodium and chloride ions interacting. 1.1. Kinetic Molecular Theory of Matter 4 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Molecules Interact through Attractive Forces The attractive forces between molecules are known as the intermolecular forces. These forces affect the spacing between molecules. The stronger the interaction between two molecules, the smaller their distance will be. The strength of the attractive force at a given temperature can be used to differentiate the states of matter. Solids have particles with strong intermolecular forces such that their particles are very close to one another. Liquids have intermediate intermolecular forces. This makes liquid particles farther from one another compared to those in solids. Gases, on the other hand, have particles that are very far apart from one another due to weak intermolecular forces. Molecules Are in Constant Random Motion All molecules are in constant random motion. The extent of their motion varies depending on the temperature and strength of the interaction between the particles. Solids, due to their strong intermolecular forces, have restricted motion. The particles of solids are only able to vibrate back and forth around a specific point or location. Liquids, having intermediate intermolecular forces, are able to move past each other. Since their particles are still close to one another, the motion is restricted to small distances as they will collide with another molecule. Gases, having weak intermolecular forces, are able to move in relatively long distances before colliding with another molecule. This happens because the particles are very far apart from one another. Temperature Is a Measure of the Average Kinetic Energy Kinetic energy refers to the energy of particles in motion. Since all molecules are in constant random motion, they contain kinetic energy. The higher the kinetic energy, the more active the particles are. Temperature is a measure of the average kinetic energy of molecules. Increasing the temperature will result in a faster motion of the particles. This can be used to describe phase changes. 1.1. Kinetic Molecular Theory of Matter 5 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids ice water steam molecules in ice molecules in water molecules in steam Fig. 1.1.1. Nanoscale representations of the three states of matter States of Matter Matter can be described in terms of its physical state. A solid is characterized by having a rigid shape and fixed volume. Unlike solids, liquids and gases do not have a definite shape. They take the shape of their container. Liquids are similar to solids in such a way that their volumes do not change significantly with varying temperatures and pressure. Gases, on the other hand, have volumes that depend on temperature and pressure. How can the kinetic molecular theory explain the properties of each state of matter? 1.1. Kinetic Molecular Theory of Matter 6 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Table 1.1.3. Characteristic properties of the states of matter State of Shape Volume Compressibility Matter solid fixed shape fixed volume virtually incompressible liquid depends on the fixed volume only slightly container compressible gas depends on the assumes the volume of very compressible container the container Based on the kinetic molecular theory of matter, the state of a matter is determined by two factors—temperature and strength of intermolecular forces. At lower temperatures, intermolecular forces determine the state of a substance. Substances with intermediate to strong intermolecular forces will form a condensed phase, either solid or liquid. Those with weak intermolecular forces will be in the gaseous state. How does the kinetic molecular theory explain phase changes? If we take into consideration the same set of molecules, then its state will be determined by the temperature. Recall that a higher temperature means a higher average kinetic energy. In other words, the particles will have enough energy to move around faster. Let’s take ice as an example. The water molecules in ice are only capable of vibrating back and forth to a specific location since it is in the solid phase. Increasing the temperature will provide enough kinetic energy to overcome their strong intermolecular forces. This will allow the molecules to move past one another. In this process, the solid becomes a liquid in a process called melting. In the same manner, when liquid water is heated, its particles are able to move past one another in relatively longer distances. The process in which liquid is converted to a gas is called vaporization. 1.1. Kinetic Molecular Theory of Matter 7 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Did You Know? Ice-skating is possible since the molecules in ice are farther apart than they are in liquid water. Increasing the pressure on a substance is similar to compressing the substance. When you compress a substance, its particles will become closer to one another. When you ice-skate, your body weight exerts high pressure onto the ice surface. Since the particles in ice are not yet the closest possible arrangement, they rearrange to form liquid water. You can glide through the ice due to the liquid water that forms under your skates. How does the kinetic molecular theory describe phases and phase changes? Key Points ___________________________________________________________________________________________ The kinetic molecular theory states that: ○ Matter is composed of small particles. ○ The molecules interact with one another through attractive forces. The strength of these forces is related to the distance between the particles. ○ These molecules are always in constant random motion. ○ The temperature of a substance is a measure of the average kinetic energy of the molecules. Solids have particles with strong intermolecular forces that cause the particles to be close together. This causes the particles’ motion to be restricted to vibrations. Liquids have particles with intermediate intermolecular forces that cause the particles to be farther apart from one another than in solids. This allows the particles to move about but in relatively short distances. 1.1. Kinetic Molecular Theory of Matter 8 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids Gases have particles with negligible intermolecular forces that cause the particles to be very far apart from one another. Due to the large distances between particles, the molecules are able to move in long distances. The average kinetic energy of the molecules can be measured by determining the temperature. The physical state of matter is affected by both kinetic energy and intermolecular forces. At low temperatures, intermolecular forces dominate. At high temperatures, the molecules have higher kinetic energy and will be able to overcome the intermolecular forces present. ___________________________________________________________________________________________ Check Your Understanding A. Identify the term described in each of the following items: ___________________________ 1. This theory explains how microscopic parameters relate to macroscopic properties of matter. ___________________________ 2. This is the state of matter that is rigid. It has a definite shape and volume and is not compressible. ___________________________ 3. This term refers to the interactions between particles. ___________________________ 4. This is a measure of the average kinetic energy of particles. ___________________________ 5. This is a measure of the average kinetic energy of particles. B. Write T if the statement is true. Otherwise, write F. ___________________________ 1. Matter is composed of small particles. ___________________________ 2. The particles comprising matter are stationary. 1.1. Kinetic Molecular Theory of Matter 9 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids ___________________________ 3. The speed at which the particles are moving depends on the temperature. ___________________________ 4. Solids have particles farthest from one another. ___________________________ 5. Gases have strong intermolecular forces. ___________________________ 6. Liquids have the largest distances between particles. ___________________________ 7. At low temperatures, the kinetic energy of the particles determines the physical state. ___________________________ 8. At high temperatures, the particles are most likely to form the closest possible arrangement. ___________________________ 9. Both kinetic energy and intermolecular forces affect the physical state of matter. __________________________ 10. At higher temperatures, molecules tend to move faster. C. Identify the state of matter being described below. ___________________________ 1. The particles vibrate at a specific location only. ___________________________ 2. The particles move about in relatively short distances. ___________________________ 3. The particles move in longer distances. ___________________________ 4. The particles are held together by strong intermolecular forces. ___________________________ 5. The particles have negligible intermolecular forces. Challenge Yourself A. Describe the phase changes using the kinetic molecular theory. Evaluate whether the changes require an increase or decrease in temperature. 1.1. Kinetic Molecular Theory of Matter 10 Unit 1: Intermolecular Forces of Attraction and Solids and Liquids B. Examine the following scenarios. Select the physical state that is most likely to be present. 1. Substance P is at 0°C. Its particles are found to be in close proximity to one another. The particles are only capable of vibrating in their specific locations. 2. Substance Q is at 30°C. The particles are moving in short distances before colliding with another particle. The intermolecular force between these particles is of intermediate strength. 3. Substance R is at 25°C. The particles have negligible interactions and are moving in longer distances before colliding with another particle. Bibliography Brown T.L., et al. Chemistry: The Central Science. Pearson Prentice-Hall, 2005. Boundless. “Kinetic Molecular Theory and Gas Laws.” Boundless Chemistry. Accessed August 12, 2016. https://www.boundless.com/chemistry/textbooks/boundless-chemistry-textbook/ga ses-5/kinetic-molecular-the Chang, Raymond, and Kenneth A. Goldsby. General Chemistry: The Essential Concepts. New York: McGraw-Hill, 2014. Petrucci, Ralph H. General Chemistry: Principles and Modern Applications. Toronto, Ont.: Pearson Canada, 2011. Silberberg, Martin S. 2007. Principles of General Chemistry. McGraw-Hill Company. 2007. 1.1. Kinetic Molecular Theory of Matter 11