Intermolecular Forces of Liquids and Solids PDF

INTERMOLECULAR FORCES; LIQUIDS AND SOLIDS BY: MRS. MARIA NIÑA C. CABRERA mncc2025  Learning Competencies (Week 1)  Use kinetic molecular model to explain properties of liquids and solids.  Describe and differentiate the types of intermolecular forces.  Describe the follo...

INTERMOLECULAR FORCES; LIQUIDS AND SOLIDS BY: MRS. MARIA NIÑA C. CABRERA mncc2025  Learning Competencies (Week 1)  Use kinetic molecular model to explain properties of liquids and solids.  Describe and differentiate the types of intermolecular forces.  Describe the following properties of liquids and explain the effect of intermolecular forces on these properties: surface tension, viscosity, vapor pressure, boiling point, and molar heat of vaporization.  Explain the properties of water with its molecular structure and intermolecular forces.  Describe the difference in structure of crystalline and amorphous solids. mncc2025 mncc2025 mncc2025  I. KINETIC MOLECULAR THEORY OF MATTER BY: MRS. MARIA NIÑA C. CABRERA mncc2025  Can you describe them? mncc2025  KINETIC MOLECULAR THEORY OF MATTER “Matter is made up of particles that are constantly moving. All particles have energy, but the energy varies depending on the temperature the sample of matter is.” mncc2025 https://courses.lumenlearning.com  KMT describes the states of matter in terms of: 1. Arrangement of particles 2. Kinetic energy of particles 3. Particle motion 4. Attractive forces between particles 5. Intermolecular forces mncc2025  KINETIC MOLECULAR THEORY ▪ Helps understand the behavior of gases. ▪ Provides a model for ideal gases – a hypothetical gas that perfectly fits all the assumptions of the KMT. mncc2025  5 ASSUMPTIONS OF KMT 1. Gases consist of large numbers of tiny particles that are far apart relative to their size. 2. Collisions between gas particles and between particles and container walls are elastic collisions. mncc2025  5 ASSUMPTIONS OF KMT 3. Gas particles are in continuous, rapid, random motion, therefore possessing kinetic energy. 4. There are no forces of attraction between gas particles. 5. The temperature of a gas depends on the average kinetic energy of the particles of the mncc2025 gas.  KMT and PROPERTIES OF LIQUID ▪ LIQUID – A form of matter that has a definite volume and takes the shape of its container. ▪ FLUID – a substance that can flow and therefore takes the shape of its container. mncc2025  KMT and PROPERTIES OF LIQUID ▪ Relatively high density ▪ Relatively incompressibility ▪ Ability to diffuse ▪ Surface tension ▪ Capillary action mncc2025  KMT and PROPERTIES OF LIQUID ▪ Vaporization – the process by which a liquid changes to a gas. ▪ Evaporation – the process by which particles escape from the surface of non- boiling liquid and enter a gas state. mncc2025  KMT and PROPERTIES OF LIQUID ▪ Boiling – the change of a liquid to bubbles of vapor that appear throughout the liquid. ▪ Freezing – the physical change of a liquid to a solid by removal of energy as heat. mncc2025 mncc2025 mncc2025 mncc2025  KMT and PROPERTIES OF SOLID ▪ SOLID – particles are the closest. ▪Arrangement of particles is very ordered. ▪Movement of particles is mainly vibrational. mncc2025  KMT and PROPERTIES OF SOLID ▪ Definite shape and volume ▪ Definite melting point ▪ High density and incompressibility ▪ Low rate of diffusion mncc2025  KMT and GAS ▪ GAS – A substance possessing perfect molecular mobility and the property of indefinite expansion, as opposed to a solid or liquid. mncc2025  KMT and PROPERTIES OF GAS ▪ Expansion ▪ Fluidity ▪ Low density ▪ Compressibility mncc2025  KMT and PROPERTIES OF GAS ▪ Diffusion – spontaneous mixing of the particles of two substances caused by their random motion. ▪ Effusion – process by which gas particles pass through a tiny opening. mncc2025 mncc2025  Deviation from an Ideal Gas ▪ Real gas – A gas that does not behave completely according to the assumptions of KMT. ▪ Noble gases, like He and Ne, act like ideal gases at a wide range of temperatures and pressures. mncc2025  COMPARISON OF SOLID AND LIQUID CRITERIA SOLID LIQUID Particle Arrangement Movement Held by very Held together by strong forces of strong forces of attraction attraction Particles are not free to Particles are able to move slide past one another mncc2025 Particles vibrate about in fixed positions mncc2025  II. INTERMOLECULAR FORCES OF ATTRACTION BY: MRS. MARIA NIÑA C. CABRERA mncc2025  ELECTRONEGATIVITY It is a measure of an atom to attract electrons toward itself. Ionic bond - ΔEN ≥1.7 Polar covalent bond - 1.7 > ΔEN > 0.4 Nonpolar covalent bond - ΔEN ≤0.4 mncc2025  POLARITY It refers to separation of charges in a molecule or the existence of partial charges in the overall structure of a molecule. mncc2025  POLARITY 1.Difference in electronegativity of bonded species. The higher the difference between the electronegativities of the bonded atoms, the more polar their bond gets. mncc2025  POLARITY 2.Asymmetry of the molecules. Even though there is a difference in the EN of bonded atoms, the resulting molecule may not be polar if the entire molecule is symmetric. mncc2025  A molecule will be nonpolar if: ▪ All of the terminal atoms (or groups) are the same. ▪ All of the terminal atoms (or groups) are symmetrically arranged around the central atom. ▪ The terminal atoms (or groups) have the same charges. Example: Carbon dioxide mncc2025  A molecule will be polar if: ▪ One or more terminal atoms differ from each other. ▪ At least one polar bond is present. ▪ The terminal atoms are not symmetrically arranged ▪ The molecule has one slightly positive end and one slightly negative end. mncc2025 Example: water  INTERMOLECULAR FORCES ▪ These are the attractive forces between particles. ▪ They are distinctly different from the bonds that occur within particles. ▪ The type of intermolecular forces present depends on the type of particle present. mncc2025  1. DIPOLE-DIPOLE FORCES These forces occur between the oppositely charged poles of polar molecules. mncc2025  DIPOLE-INDUCED DIPOLE A polar molecule c an induc e a temporary dipole in a nonpolar molecule by temporarily attracting its electrons. Termed dipole-induc ed dipole, this attractive force is short-ranged and considered weaker than dipole-dipole interactions. mncc2025  2. ION-DIPOLE FORCES ▪ These forces occur between an ion and a polar molecule. ▪ An ion will form an attraction with an oppositely- charged pole of a neighboring molecule. ▪ Salt water is loaded with ion-dipole attractions. ▪ Na (+) ions are attracted to the negative poles of water molecules. ▪ Cl (-) ions are attracted to the positive poles of water molecules. mncc2025  2. ION-DIPOLE FORCES mncc2025  3. LONDON DISPERSION FORCES A German-American physicist, Fritz London proposed a weak intermolecular forces that arise from the interactive forces between instantaneous dipoles or induced dipoles in molecules called London dispersion forces or dispersion forces. mncc2025 mncc2025  London dispersion forces tend to be: Stronger between molecules that are easily polarized. Weaker between molecules that are not easily polarized. mncc2025  VAN DER WAALS FORCE ▪ It is named after a Dutch physicist Johannes Diderik van der Waals. ▪ This force of attraction between two nonpolar substances. ▪ Molecules can attract each other at moderate distances and repel each other at close range. ▪ The attractive forces are collectively called Van der Waals forces. These are much weaker than chemical bonds. mncc2025  4. HYDROGEN BONDS ▪ These occur between polar molecules that contain oxygen, nitrogen or fluorine atom covalently bonded to a hydrogen atom. ▪ The intermolecular attraction happens between the partially negatively charged oxygen, fluorine or nitrogen and the partially positively charged hydrogen of a neighboring molecule. mncc2025  4. HYDROGEN BONDS Hydrogen bonds are relatively strong intermolecular forces. mncc2025 mncc2025 mncc2025  III. PROPERTIES OF LIQUIDS BY: MRS. MARIA NIÑA C. CABRERA mncc2025  1. SURFACE TENSION It is the force that causes the molecules on the surface of a liquid to “tighten their hold to one another,” creating the effect of a thin membrane on the surface. Substances with strong attractive forces between the molecules have high surface tensions. Surface tension is temperature-dependent; it decreases as temperature increases. mncc2025  2. VISCOSITY It is a measure of a fluid’s resistance to flow. Polar molecules and molecules with complex structures tend to have higher viscosity, being less able to slip and slide over one another than those with simple structures and less polarity. mncc2025 mncc2025  3. CAPILLARY ACTION ▪ It is the spontaneous rising of a liquid in a narrow tube, is also observed in liquids. ▪ It is the rise or depression of a liquid in a small passage such as tube of a small cross-sectional area, the spaces between the fibers of a towel or the openings of a porous material. mncc2025 mncc2025 mncc2025 mncc2025 mncc2025  4. VAPOR PRESSURE ▪ The pressure exerted by a vapor that is in equilibrium with its solid or liquid form. ▪ A substance with a high vapor pressure at normal temperature is often referred to as “volatile”. mncc2025  VAPORIZATION Conversion of a liquid to a gas or vapor mncc2025  IV. PROPERTIES OF WATER BY: MRS. MARIA NIÑA C. CABRERA mncc2025  WATER It is a very remarkable substance with its simple composition and structure. It has unique properties. An evidence of its uniqueness is that it is the only natural substance that is found in all three phases: liquid, solid (ic e), and gas (steam) at temperature normally existing in our planet. mncc2025  PROPERTIES OF WATER ▪ Pure water is odorless and tasteless. ▪ Density ▪ H-bonded ▪ Boiling point ▪ Specific heat ▪ Solvent action ▪ Surface tension mncc2025 mncc2025  V. PROPERTIES OF SOLID BY: MRS. MARIA NIÑA C. CABRERA mncc2025  Which is more solid? mncc2025 mncc2025  SOLID Particles are more attracted with one another which allows them to be in conta ct in fixed positions, thus, occupying specific amounts of space. This explains the definite shape and volume of solids. mncc2025  SOLID Particles have less kinetic energy, so movement of the particles is very limited, though possible, like vibrational motion about a fixed point. mncc2025  SOLID The temperature at which a solid melts is called melting point. “The stronger the attractive forces, the higher the melting point.” mncc2025  SOLID ▪ The amount of heat required to c ompletely melt a solid, once it has reached its melting point is called heat of fusion. ▪ The change from solid to gas without passing through a liquid state is called sublimation. mncc2025  PROPERTIES OF SOLID 1. Electrical & thermal conductivity 2. Malleability 3. Ductility 4. Melting point 5. Solubility 6. Density mncc2025  CLASSES OF SOLIDS 1. Crystalline solids 2. Amorphous solids mncc2025  1. CRYSTALLINE SOLID It is a solid in which the constituent particles (atoms, ions, or molecules) have an orderly arrangement, that is, it has regularly arranged structure units with characteristics geometric forms. Thus, crystals show regular shapes which reflect the arrangement of the particles mncc2025 between them.  2. AMORPHOUS SOLID ▪ The word amorphous means that the solid does not always adopt the same form. Its constituent particles are randomly arranged. ▪ Examples: asphalt, rubber, glass, plastic mncc2025 mncc2025 mncc2025 mncc2025 mncc2025 mncc2025 mncc2025