General Chemistry II Chapter 1 PDF

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Senior High School (STEM)

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general chemistry kinetic molecular theory intermolecular forces chemistry

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This document details the first chapter of General Chemistry II for senior high school students, covering the kinetic molecular theory of solids and liquids, and intermolecular forces such as dipole-dipole, hydrogen bonding, London dispersion forces, and the connection between these forces and liquid properties like surface tension, viscosity, and vapor pressure.

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# General Chemistry II ## Chapter 1: The Kinetic Molecular Model and Intermolecular Forces of Attraction in Matter ### General Chemistry 2 - Senior High School (STEM) ### Section 1.1: Kinetic Molecular Theory of Solids and Liquids - EQ: Why do solids and liquids behave differently? ### Kinetic M...

# General Chemistry II ## Chapter 1: The Kinetic Molecular Model and Intermolecular Forces of Attraction in Matter ### General Chemistry 2 - Senior High School (STEM) ### Section 1.1: Kinetic Molecular Theory of Solids and Liquids - EQ: Why do solids and liquids behave differently? ### Kinetic Molecular Theory - The Kinetic Molecular Theory explains the properties of solids and liquids in terms of intermolecular forces of attraction and the kinetic energy of the individual particles. - **Postulates of the Kinetic Molecular Theory**: 1. All matter is made up of tiny particles. 2. These particles are in constant motion. 3. The speed of a particle is proportional to temperature. Increased temperature means greater speed. 4. Solids, liquids, and gases differ in distances between particles, in the freedom of motion of particles, and in the extent to which the particles interact. - A diagram is shown to illustrate the states of matter: solid, liquid and gas. Particles in the solid state are closely packed and regularly arranged. Particles in the liquid state are closely packed but irregularly arranged. Particles in the gas state are far apart and randomly arranged. ### Activity 1 - Compare the distances among molecules in the gas, liquid, and solid, and rank the phases in increasing distance between particles. - Describe the characteristic movement of the particles of gas, liquid, and solid. - How are the molecules of gas, liquid, and solid arranged? - Arrange the three phases of matter in order of increasing volume of empty space between its molecules. ### Properties of Matter | Properties of Matter | gas | liquid | solid | |---|---|---|---| | **Volume/Shape** | Assumes volume and shape of container | Fixed volume; assumes shape of occupied part of container | Fixed volume; fixed shape (regardless of size and shape of container | | **Density** | low | high | high | | **Compressibility** | Easy to compress | Cannot be appreciably compressed | Cannot be appreciably compressed | | **Motion of Molecules** | Random, fast, cover large distances | Random, medium speed, limited distances | Vibration in place |---|---|---|---| - A diagram shows the three states of matter: gas, liquid and solid. ### General Chemistry 2 - Senior High School (STEM) ### Section 1.2: Intermolecular Forces of Attraction - EQ: How is intermolecular forces defined by nature of particles? ### Intermolecular Forces of Attraction - **INTERMOLECULAR FORCES** are attractive forces between molecules or particles in the solid or liquid state. They are weaker than intramolecular forces. - A diagram shows the intermolecular forces of attraction between the molecules of ammonia. - Intramolecular forces hold atoms together in a molecule. - The intermolecular forces of attraction in a pure substance are collectively known as **van der Waals forces**: 1. Dipole-dipole forces 2. Hydrogen bonding 3. Ion-dipole forces 4. London dispersion forces 5. Dipole-induced dipole forces ### Dipole-Dipole Forces - Dipole-dipole forces exist between polar molecules. One end of a dipole attracts the oppositely charged end of the other dipole. - A diagram shows the dipole-dipole attraction between the molecules of hydrogen chloride. ### Hydrogen Bonding - It is a special and very strong type of dipole-dipole force that exists between a hydrogen atom bound to a small and highly electronegative non-metal atom. - Hydrogen bond occurs in polar molecules containing H and any of highly electronegative elements, in particular Nitrogen, Fluorine, and Oxygen. - A diagram shows the hydrogen bonding between the molecules of methanol and water. ### Ion-Dipole Force - It acts between an ion (either positive or negative) and a polar molecule. - This explains the solubility of ionic compounds in water, which is polar molecule. - A diagram shows the ion-dipole attraction between the ions of sodium chloride and the molecules of wate ### Ion-Dipole Force - The ions and the oppositely charged ends of the polar water molecules overcome the attraction between ions themselves. Each ion becomes separated and water molecules cluster around it. - A diagram shows the ion-dipole attraction between the ions of sodium chloride and the molecules of water, and the water molecules clustering around the ions. ### London Dispersion Forces - It is the weakest type of intermolecular force. - When two non-polar molecules approach each other, an instantaneous dipole moment forms. - This force is sometimes called an induced dipole-induced dipole attraction. - A diagram shows the London dispersion forces between the molecules of a non-polar substance. <start_of_image> This force is sometimes called an induced dipole-induced dipole attraction. ### Dispersion Forces or London Forces - A diagram is shown of two non-polar molecules. The electron cloud is represented in red and blue. The electrons are unequally distributed due to the temporary dipoles, which results in an attractive force. ### Dipole-Induced Dipole Forces - Interaction between Polar and non-polar molecules. - A diagram shows the Dipole-induced dipole forces between the molecule of water and the atom of xenon. ### Activity 2 - What type of intermolecular force will act in the following substances? Justify your answer. 1. sulfur dioxide (SO₂) 2. nitrogen gas (N₂) 3. hydrogen fluoride (HF) 4. carbon dioxide (CO₂) 5. neon gas (Ne) 6. magnesium chloride (MgCl₂) dissolved in water (H₂O) ### General Chemistry 2 - Senior High School (STEM) ### Section 1.3: Intermolecular Forces and Properties of Liquids - EQ: How do intermolecular forces influence the properties of liquids? ### Intermolecular Forces and Properties of Liquids - Liquids exhibit intermolecular forces of attraction. - Properties of liquids which can be explained by intermolecular forces are: - Surface Tension - Capillary Action - Viscosity - Vapor pressure - Boiling point - Heat of vaporization - A diagram shows that liquids don’t have a simple or regular structure, but their properties can be explained qualitatively by viewing them at the particulate level. ### General Properties of Liquids - A diagram illustrates the general properties of liquids: surface tension, viscosity, capillary action, heat of vaporization, vapor pressure and boiling point. ### Surface Tension - It is the measure of the elastic force in the surface of a liquid. - It is the amount of energy required to stretch or increase the surface of a liquid by a unit area. - It is manifested as some sort of skin on the surface of a liquid or in a drop of liquid. - Surface tension allows needles and paper clips to float in water if placed carefully on the surface. It also explains why drop of water are spherical. - These intermolecular forces tend to pull the molecules into the liquid and cause the surface to tighten like an elastic film or "skin". ### Surface Tension - A diagram illustrates the surface tension of water. Molecules within a liquid are pulled in all directions by intermolecular forces. Molecules at the surface are pulled downward and sideways by other molecules, not upward away from the surface. - The liquids that have strong Intermolecular forces also have high surface tension. - A diagram shows water being poured from a bottle into a glass. ### Capillary Action - Capillary action is the tendency of a liquid to rise in narrow tubes or be drawn into small openings such as those between grains of a rock. - Capillary action, also known as capillarity, is a result of intermolecular attraction between the liquid and solid materials. - A diagram illustrates the capillary action of water in a glass tube. Water rises in the narrow tube due to the attraction between the molecules of water and the surface of the glass tube. ### Capillary Action - A diagram shows capillary action in a plant. The liquid in the diagram is coloured red and the plant is shown in two poses, one with red coloured branches and the other with red colored leaves. The plant takes up water from the soil due to the attractions between the molecules of water and the surface of the plant stems. - Two types of forces are involved in capillary action: - **Cohesion** is the intermolecular attraction between like molecules (the liquid molecules). - **Adhesion** is an attraction between unlike molecules (such as those in water and in the particles that make up the glass tube). - These forces also define the shape of the surface of a liquid in a cylindrical container (the meniscus!). ### Capillary Action - When the cohesive forces between the liquid molecules are **greater than the adhesive forces** between the liquid and the walls of the container, the surface of the liquid is **convex**. - When the cohesive forces between the liquid molecules are **lesser than the adhesive forces** between the liquid and the walls of the container, the surface of the liquid is **concave**. ### Capillary Action - A diagram illustrates the meniscus of mercury and water in a glass tube. ### Viscosity - It is the resistance of a liquid to flow. - It is *loosely* referred to as the thickness or thinness of a liquid. - Syrup and oil flow more slowly than water and are thus described as more viscous. - The viscosity of *liquid* depends on their Intermolecular attraction. - The stronger the intermolecular force, the higher is the liquid’s viscosity. ### Viscosity - A diagram shows a marble falling through a liquid. - Long-chained substances like oil have greater intermolecular forces, because there are more atoms that can attract one another, contributing to the substance's total attractive forces. - A diagram shows a bottle of cooking oil labelled “Sana Oil.” - Honey, a concentrated solution of sugar, is also highly viscous because of the hydrogen bonding that forms as a result of the numerous -OH groups of sugar molecules. - A diagram shows a cartoon to illustrate honey's viscosity. ### Vapor Pressure - It is the pressure exerted by its vapor when in equilibrium with liquid or solid. - When liquid or solid substance is made to evaporate in a closed container, the gas exerts a pressure above the liquid. ### Vapor Pressure - Substances with relatively strong intermolecular forces will have low vapor pressure because the particles will have difficulty escaping as a gas. - **Example**: 1. Water (H₂O), (Hydrogen Bonding) has a vapor pressure of 0.03 atm. 2. Ethyl Ether (C₄H₁₀O), dipole-dipole & London Force), has a vapor pressure of 0.68 atm. ### Boiling Point - The boiling point of a liquid is the temperature at which its vapor pressure is equal to the external or atmospheric pressure. - Increasing the temperature of a liquid raises the kinetic energy of its molecules, until such point where the energy of the particle movement exceeds the intermolecular forces that hold them together. ### Boiling Point - The liquid molecules then transform to gas and are seen as bubbles that rises to the surface of the liquids and escape to the atmosphere. - The temperature at which a liquid boils under 1 atmospheric pressure (1atm) is referred to as its normal boiling point. ### Boiling Point - At higher altitude, the atmospheric pressure is lower, hence, the boiling point will subsequently decrease. - The greater the intermolecular force, the higher the energy needed to increase the kinetic energy of the molecules to break these forces. ### Boiling Point | Substance | Boiling Point* (°C) | ΔHvap (kJ/mol) | |---|---|---| | Argon (Ar) | -186 | 6.3 | | Benzene (C₆H₆) | 80.1 | 31.0 | | Diethyl ether (C₂H₅OC₂H₅) | 34.6 | 26.0 | | Ethanol (C₂H₅OH) | 78.3 | 39.3 | | Mercury (Hg) | 357 | 59.0 | | Methane (CH₄) | -164 | 9.2 | | Water (H₂O) | 100 | 40.79 | |---|---|---| ### Heat of Vaporization - Molar heat of vaporization (Hvap) is the amount of heat required to vaporize one mole of substance at its boiling point. - The application of heat disrupts the intermolecular forces of attraction of the liquid molecules and allows them to vaporize. ### Heat of Vaporization - Boiling point generally increases as molar heat of vaporization increases. - The Hvap is also determined by the strength of intermolecular forces between molecules. ### Heat of Vaporization | Substance | ΔHvap (kJ/mol) | Boiling Point* (OC) | |---|---|---| | Argon (Ar) | 6.3 | -186 | | Pentane (C₅H₁₂) | 26.5 | 36.1 | | Acetone (CH₃COCH₃) | 30.3 | 56.5 | | Ethanol (C₂H₅OH) | 39.3 | 78.3 | | Water (H₂O) | 40.79 | 100 | |---|---|---| ### Structure and Properties of Water - At room temperature, pure water is a colorless, odorless and tasteless liquid. - It turns to ice, its solid form at 0 °C and 1 atm. - At 100 °C, it becomes gas, commonly known as steam. ### Unique Properties of Water - **Unique properties of water include**: 1. Water is a good solvent. 2. Water has a high specific heat: specific heat is the amount of heat or energy needed to raise the temperature of one gram of a substance by 1 °C. 3. The boiling point of water is unusually high. 4. Solid water is less dense, and in fact, floats on liquid water: unlike all other liquids, the molecules in solid water are actually farther apart than they are in liquid water. When solid water forms, the hydrogen bonds result in a very open structure with unoccupied spaces, causing the solid to occupy a larger volume than the liquid. This makes ice less dense than liquid water, causing ice to float on water. ### Unique Properties of Water - A diagram shows the hydrogen bonds in the structure of ice. ### Unique Properties of Water - A diagram shows the hydrogen bonding between the molecules of ice. ### General Chemistry 2 - Senior High School (STEM) ### Section 1.4: Types and Properties of Solids - EQ: How do you describe solids? ### Types and Properties of Solids - **Solid** can be classified as **crystalline or amorphous** based on the arrangement of their particles. - **Crystalline solids** have highly regular arrangement of particles, while **amorphous solids** have considerable disorder in their structure. ### Amorphous Solids - Amorphous solids, such as glass, are formed rapidly that its constituent particles do not have time to align or organize into a more crystalline lattice. - A diagram shows several examples of amorphous solids: glass, biological tissue, dense colloids, emulsions (like mayonnaise), a close up view of foam, bulk metallic glass, and sand. ### Amorphous Solids - A diagram shows several examples of amorphous solids: charcoal, rubber bands, glass paper weights and plastic lunch boxes. ### Crystalline Solids - **Crystalline Solids** have well-defined crystal lattice: a lattice is a three-dimensional system of points designating the positions of the components (ions, atoms, or molecules) that makeup a crystal. - A diagram shows the lattice structure of a crystalline solid. ### Crystalline Solid - A diagram shows the lattice structure of a crystalline solid and a pile of table salt. ### Crystalline Solids - A **unit cell** is the *smallest repeating unit of lattice*. - Diagrams show the unit cells of different types of crystal lattices: - Cubic - Tetragonal - Orthorhombic - Monoclinic - Hexagonal - Rhombohedral - Triclinic ### Classification of Crystalline Solids | TYPES | COMPONENTS THAT OCCUPY THE LATTICE POINTS | TYPE OF INTERACTION BETWEEN COMPONENTS OF LATTICE | TYPICAL PROPERTIES | EXAMPLES | |---|---|---|---|---| |**IONIC** | Ions | Ionic | Hard, high melting point; insulating as solid but conducting when dissolved | NaCl | | **MOLECULAR** | Discrete molecules | Dipole-dipole or London dispersion | Soft; low melting point | Ice, dry ice | | **METALLIC** | Metal atoms | Delocalized covalent | Wide range of hardness and melting points | Silver, Iron, Brass | **NETWORK** | Nonmetal atoms | Directional covalent | Hard, high melting point | Diamond | | **GROUP 8A** | Noble gases | London dispersion forces | Very low melting point | Argon | |---|---|---|---|---| ### Classification of Crystalline Solids - A diagram shows the four different types of crystalline solids: ionic (sodium chloride), molecular (ice), metallic (iron), and network (diamond). ### General Chemistry 2 - Senior High School (STEM) ### Section 1.5: Phase Changes and Phase Diagrams - EQ: When does *equilibrium* exist between the phases of a substance? ### Phase Changes - **Phase Changes** are transformations of matter from one physical state to another. - They occur when *energy* is added or removed from a substance. - They are characterized by changes in molecular order; *molecules in the solid phase have the greatest order, while those in the gas phase have the greatest randomness or disorder*. ### Phase Changes - What changes in molecular order occur during phase changes? A diagram illustrates the molecular order versus disorder in the solid, liquid and gaseous state. ### Types of Phase Changes - Diagram shows the types of phase changes for the three states of matter. - **Melting** (solid to liquid) - **Freezing** (liquid to solid) - **Vaporization** (liquid to gas) - **Condensation** (gas to liquid) - **Sublimation** (solid to gas) - **Deposition** (gas to solid) ### Phase Changes - How does a change in energy affect *phase changes*? - A diagram shows the temperature-time graph for heating a substance from solid to gas state. - How does a change in energy affect *phase changes*? A diagram shows the temperature-time graph for cooling a substance from solid to gas state. ### Phase Diagrams - How can this effect be achieved using CO₂ or dry ice? - A diagram shows a fog machine. ### Phase Diagrams - Carbon *dioxide* cannot exist as a liquid at atmospheric pressure; the dry ice sublimates and instantly produces a gas, condensing water vapor, and creating a thick white fog. - It is usually used in fog machines. ### Phase Diagrams - What does LPG stand for? How can a gas be liquefied? - A diagram shows a blue cylinder of LPG. ### Phase Diagrams - **Liquefied Petroleum Gas (LPG)** is a flammable mixture of hydrocarbon gases that are liquefied at high pressure. It is usually used as fuel in heating appliances, cooking equipment, and vehicles. ### Phase Diagrams - It is a *graphical representation* of the *physical states* of a substance under different conditions of temperature and pressure. - It gives the possible combinations of pressure and temperature at which *certain physical state or states* a substance would be observed. ### Phase Diagrams - A diagram shows a phase diagram. ### Features of Phase Diagram - Phase diagrams are plots of pressure (usually in atmospheres) versus temperature (usually in degrees Celsius or Kelvin). - **Key features of a Phase Diagram**: 1. Three Areas (Solid, Liquid, Gas) 2. The Three Lines 3. The Two important points ### A. The Three Areas - The three areas are marked solid, liquid, and vapor. *Under a set of conditions in the diagram*, a substance can exist in a solid, liquid, or vapor (gas) phase. - A diagram shows the three phases of a substance. ### B. The Three Lines - The lines that serve as boundaries between physical states represent the combinations of pressures and temperatures at which two phases can exist in equilibrium. - In other words, these lines define phase change points. ### Melting (or Freezing Curve) - **The green line** divides the solid and liquid phases, and *represents melting* (solid to liquid) and *freezing* (liquid to solid) points. - A diagram shows the melting curve of a substance. ### Melting (or freezing) curve - Melting (or freezing) curve – the *curve on a phase diagram* which *represents the transition* between liquid and sold states. - It shows the effect of pressure on the melting point of the solid: anywhere on this line, there is equilibrium between the solid and the liquid. ### Vaporization (Condensation Curve) - **The blue line** divides the *liquid and gas phases*, and *represents vaporization* (liquid to gas) and *condensation* (gas to liquid) points. - A diagram shows the vaporization curve of a substance. ### Vaporization (Condensation Curve) - The curve on a phase diagram which represents the transition between gaseous and liquid states. It shows the effect of pressure on the boiling point of the liquid. - Anywhere along this line, there will be equilibrium between the liquid and the vapor. ### Sublimation (or deposition) curve - **The red line** divides the solid and gas phases, and *represents sublimation* (solid to gas) and *deposition* (gas to solid) points. - A diagram shows the sublimation curve of a substance. ### Sublimation (or deposition) curve - The curve on a phase diagram which represents the transition between gaseous and solid states. - It represents the effect of *increased temperature* on a *solid* at a very low constant pressure, lower than the *triple point*. ### C. The Two important Points - The **triple point** is the *combination of pressure and temperature* at which all three phases of matter are at equilibrium. - It is the point on a phase diagram at which the *three states of matter coexist*. The *lines that represent the conditions of solid-liquid, liquid-vapor, and solid-vapor equilibrium meet at the triple point*. ### C. The Two important Points - A diagram shows the triple and critical points on a phase diagram. ### C. The Two important Points - The **critical point** terminates the *liquid/gas phase line*. It is the *set of temperature and pressure* on a phase diagram where the *liquid and gaseous phases of a substance merge together into a single phase*. - Beyond the temperature of the critical point, the *merged single phase* is known as a **supercritical fluid**. ### C. The Two important Points - A diagram shows the critical point on a phase diagram. ### Phase Diagram for Water - A diagram shows the phase diagram of water. ### Phase Diagram for a Substance - A diagram shows the phase diagram of a substance. ### Activity! - Constructing a Phase Diagram - Visualize a substance with the following points on the phase diagram: - a triple point at 0.05 atm and 150 K; - a normal melting point at 175 K; - a normal boiling point at 350 K; and - a critical point at 2.0 atm and 450 K. - The solid liquid line is "normal" (meaning positive sloping). - For this, complete the following: 1. Roughly sketch the phase diagram, using units of atmosphere and Kelvin. Label the area 1, 2, and 3, and points T and C on the diagram. 2. Describe what one would see at pressures and temperatures above 2.0 atm and 450 K. 3. Describe the phase changes from 50 K to 250 K at 1.5 atm. 4. What exists in a system that is at 1 atm and 350 K? 5. What exists in a system that is at 1 atm and 175 K?

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