General Chemistry 2 Past Paper PDF

GENERAL CHEMISTRY 2  INTERMOLECULAR FORCES OF LIQUIDS AND SOLIDS 01. THE KINETIC MOLECULAR THEORY OF LIQUIDS AND SOLIDS 02. INTERMOLECULAR FORCES OF ATTRACTION 03. PROPERTIES OF LIQUIDS 04. STRUCTURE AND PROPERTIES OF WATER 05. TYPES AND PROPERTIES OF SOLIDS...

GENERAL CHEMISTRY 2  INTERMOLECULAR FORCES OF LIQUIDS AND SOLIDS 01. THE KINETIC MOLECULAR THEORY OF LIQUIDS AND SOLIDS 02. INTERMOLECULAR FORCES OF ATTRACTION 03. PROPERTIES OF LIQUIDS 04. STRUCTURE AND PROPERTIES OF WATER 05. TYPES AND PROPERTIES OF SOLIDS TOPICS TO 06. PHASE CHANGES COVER 01. THE KINETIC MOLECULAR THEORY OF LIQUIDS AND SOLIDS LEARNING TARGETS At the end of this lesson, the students must be able to use the kinetic molecular model to explain the properties of liquids and solids; describe and differentiate the types of intermolecular forces and predict the type of intermolecular forces possible for a molecule; describe and explain the effects of intermolecular forces on the following properties of liquids: surface tension, viscosity, vapor pressure, boiling point, and molar heat of vaporization; explain the properties of water to its molecular structure and intermolecular forces; describe the different structures of crystalline and amorphous solids; describe the differences between crystals and their properties; describe the nature of the following phase changes in terms of energy change increase or decrease of molecular order: solid-liquid, liquid-vapor, and solid-vapor; and interpret the phase diagram of water andcarbon dioxide. KMT OF LIQUIDS AND SOLIDS kinetic molecular theory states that molecules are in constant motion. Since molecules are in constant motion, the thing that determines whether something is a solid, liquid, or gas depends on how much motion those molecules are in. INTERMOLECULAR FORCES IMF holds molecules together. They’re doing the opposite thing of kinetic energy. They’re opposing kinetic energy, because the closer intermolecular- or the larger the intermolecular forces are, the closer the molecules are going to be together. INTERMOLECULAR FORCES POLAR AND NON-POLAR DIPOLE MOMENT Dipole moment (μ) is the measure of net molecular polarity, which is the magnitude of the charge 𝑄 at either end of the molecular dipole times the distance 𝑟 between the charges. μ=Q×r 1. DIPOLE-DIPOLE INTERACTION refers to the formation of a positive pole and negative pole of a molecule. It is evident in polar molecules, which exhibit dipole-dipole interaction. 2. DIPOLE-INDUCED DIPOLE INTERACTION A dipole-induced dipole attraction is a weak attraction that results when a polar molecule induces a dipole in an atom or in a nonpolar molecule by disturbing the arrangement of electrons in the nonpolar species. 3. DISPERSION FORCES The London dispersion force is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. This force is sometimes called an induced dipole-induced dipole attraction. 4. ION-DIPOLE ATTRACTION An ion-dipole interaction is the intermolecular force of attraction between a charge ion (cation or anion) and a molecule. It is found commonly in the solution where ionic compounds dissolve in polar solvents. 5. ION-INDUCED DIPOLE INTERACTION An ion-induced dipole force occurs when an ion interacts with a non-polar molecule. Like a dipole-induced dipole force, the charge of the ion causes a distortion of the electron cloud in the non-polar molecule, causing a temporary partial charge. 6. HYDROGEN BONDING a special type of dipole-dipole attraction between molecules, not a covalent bond to a hydrogen atom. It results from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom and another very electronegative atom. PRACTICE Identify the types of intermolecular forces of attraction that exist between the following pairs of molecules: (a) H2O only, (b) CH4 or methane only, (c) HCl and Hl, (d) CH4, and CCl4, (e) CH3CH2OH and H2O, (f) Na+ ion and H2O, (g) NH3 and C3H8, (h) Mg+2 and C2H6 03. PROPERTIES OF LIQUIDS SURFACE TENSION The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules. is the amount of energy needed to conquer the force between molecules at the liquid’s surface and increase its surface area. Therefore, if the liquid has strong intermolecular forces, its surface tension will be high. SURFACE TENSION Cohesion the attraction between the molecules or atoms of the same substance liquid-liquid (like molecules) Adhesion the attraction between the molecules of two different substances solid-liquid (unlike molecules) VISCOSITY a liquid's resistance to flow. When the intermolecular forces of attraction are strong within a liquid, there is a larger viscosity. Some liquids, such as gasoline, ethanol, and water, flow very readily and hence have a low viscosity. Others, such as motor oil, molasses, THE STRONGER THE INTERMOLECULAR and maple syrup, flow very slowly FORCES, THE GREATER THE VISCOSITY and have a high viscosity. OF THE LIQUID VAPOR PRESURE VAPOR PRESURE VAPOR PRESURE VAPOR PRESURE  MOLAR HEAT OF BOILING POINT VAPORIZATION The boiling point is the The molar heat of vaporization (ΔHvap) is the temperature at which a liquid's amount of energy needed to for 1 mole of a vapor pressure equals the liquid to evaporate at a specific temperature. pressure outside Enthalpy, or the amount of heat present at a given standard state, is represented by the letter H THE HIGHER ΔHVAP, THE HIGHER THE BOILING POINT 04. STRUCTURE AND PROPERTIES OF WATER CHEMICAL PROPERTIES OF WATER Amphoteric Nature An amphoteric substance is one which can act as an acid or a base. While Water is neither acidic or basic it acts as both. This is because of its ability to both donate and accept protons. For acids stronger than water it acts as a base. And it acts like a acid to bases stronger than itself. CHEMICAL PROPERTIES OF WATER Hydrolysis Reaction Water has a very high dielectric constant. This results in it having a strong hydrating tendency. Water has strong reactions with ions of salts and creates hydrating shells around them. CHEMICAL PROPERTIES OF WATER Redox Reactions Water is a great source to obtain dihydrogen since it can be reduced by reacting it with highly electropositive metals such as Sodium. PHYSICAL PROPERTIES OF WATER Chemical formula H2O is the chemical formula for water, as we all know. Covalent bonds exist between the hydrogen and oxygen atoms in the water molecule. A single atom of oxygen forms a connection with two hydrogen atoms. PHYSICAL PROPERTIES OF WATER Appearance In its natural condition, water is a colourless, odourless, and tasteless liquid. Boiling Point Water has a boiling point of 100 degrees Celsius, as we all know. However, water’s comparatively high boiling point violates the periodic table’s tendency. PHYSICAL PROPERTIES OF WATER Freezing Point The same notion applies to water’s freezing point. Water has a freezing point of 0 degrees Celsius. The fact that water takes a long time to freeze (or even boil) is critical for our ecosystems and existence. Density One of the remarkable properties of water is that it is dense in its sold condition. The density of water increases as it cools up to 4°C. However, after that, water gets less dense. Ice floats in water because of this. PHYSICAL PROPERTIES OF WATER Viscosity Due to very strong intermolecular interactions, water has a high viscosity. Solvency Water is a highly effective solvent. It’s even referred to as a Universal Solvent. 05. PROPERTIES OF SOLIDS A. CRYSTALLINE SOLIDS Crystalline solids are those in which the atoms, ions, or molecules that make up the solid exist in a regular, well-defined arrangement. The smallest repeating pattern of crystalline solids is known as the unit cell, and unit cells are like bricks in a wall—they are all identical and repeating. A. CRYSTALLINE SOLIDS TYPES OF CRYSTALLINE SOLIDS 1. IONIC CRYSTALS are ionic compounds composed of cations and anions. 2. COVALENT CRYSTALS solids in which atoms are held together by strong covalent bonds. Because covalent bonds are relatively strong, covalent network solids are typically characterized by hardness, strength, and high melting points. For example, diamond is one of the hardest substances known and melts above 3500 °C. ALLOTROPES Some solid substances can exist in more than one form. ALLOTROPES ALLOTROPES ALLOTROPES ALLOTROPES TYPES OF CRYSTALLINE SOLIDS 3. MOLECULAR CRYSTALS are solids made of molecules whose attractive forces include dipole-dipole, dispersion, and hydrogen bonding. These forces are weaker than ionic and covalent bonds. Molecular solids, such as ice, sucrose (table sugar), and iodine are composed of neutral molecules. The strengths of the attractive forces between the units present in different crystals vary widely, as indicated by the melting points of the crystals. TYPES OF CRYSTALLINE SOLIDS 4. METALLIC CRYSTALS The principal constituent particles are atoms of the same metal. Usually, metals have one to four outer electrons; thus, there are empty orbitals in the last energy level. Since the atoms are closely packed, these orbitals overlap, allowing loosely bonded electrons to move form one atom to another, resulting in a "sea of electrons". B. AMORPHOUS SOLIDS An amorphous solid is that in which the constituent particles do not possess a regular three-dimensional arrangement. 1. Lack of long-range order Amorphous Solid does not have a long-range order of arrangement of their constituent particles. However, they may possess small regions of orderly arrangement. These crystalline parts of an otherwise amorphous solid are known as crystallites. B. AMORPHOUS SOLIDS 2. No sharp melting point An amorphous solid does not have a sharp melting point but melts over a range of temperatures. For example, glass on heating first softens and then melts over a temperature range. Glass, therefore, can be moulded or blown into various shapes. Amorphous solid does not possess the characteristic heat of fusion. B. AMORPHOUS SOLIDS 3. Conversion into crystalline form Amorphous solid, when heated and then cooled slowly by annealing, becomes crystalline at some temperature. That is why glass objects of ancient time look milky because of some crystallization having taken place. 06. PHASE CHANGES PHASE CHANGES A phase change is when matter changes to from one state (solid, liquid, gas, plasma) to another. PHASE CHANGES MELTING is defined as the process of converting a substance from the solid to the liquid state of matter. FREEZING A chemical that exists in its liquid state can be changed back into a solid state in a process known as fusion, which is more commonly-known as "freezing." PHASE CHANGES VAPORIZATION Vaporization, which is more often referred to as "boiling," is the complementary process in which a chemical is converted from the liquid state of matter to a gaseous physical form. CONDENSATION a substance is changed from the gaseous to the liquid state of matter. PHASE CHANGES VISUAL REPRESENTATIONS OF BOILING AND EVAPORATING, RESPECTIVELY. PHASE CHANGES SUBLIMATION is the change of state from a solid to a gas, without passing through the liquid state DEPOSITION s the change of state from a gas to a solid. PHASE CHANGES IONIZATION conditions allow the plasma to evert to a gas. Photons of sufficient energy can, on absorption, kick an electron off an atom or ion RECOMBINATION s a process by which positive ions of a plasma capture a free (energetic) electron and combine with electrons or negative ions to form new neutral atoms (gas) PHASE DIAGRAM PHASE CHANGES LIQUID-VAPOR EQUILIBRIUM when both the liquid and vapour phases of a substance are in Equilibrium. The energy needed to vaporize 1 mole of liquid is known as MOLAR HEAT OF VAPORIZATION (ΔHvap).  PHASE DIAGRAM A phase diagram is a graphical representation of the phase change of different substances under different pressure and temperature conditions.  PHASE DIAGRAM A TYPICAL PHASE DIAGRAM FOR A SUBSTANCE THAT EXHIBITS THREE PHASES —SOLID, LIQUID, AND GAS—AND A SUPERCRITICAL REGION  SUPERCRITICAL FLUID highly compressed gases which combine properties of gases and liquids in an intriguing manner.  PHASE DIAGRAM FOR WATER It is a pressure- temperature diagram that showcases water in its various states like ice, liquid, and steam under different conditions. PHASE DIAGRAMS FOR WATER The triple point of water is the end of the first curve, and at this point, the three phases of water- solid, liquid, and steam coexist.  PHASE DIAGRAM FOR CO2 It is a pressure- temperature diagram that showcases water in its various states like ice, liquid, and steam under different conditions. SOLUTIONS PHYSICAL PROPERTIES OF SOLUTION Solution is the homogeneous mixture of two or more substances. Two components: SOLUTE - the one that is being dissolved. SOLVENT - act as the dissolving medium TYPES OF SOLUTIONS A supersaturated solution comprises a large amount of solute at a temperature wherein it will be reduced, as a result, the extra solute will crystallize quickly. An unsaturated solution is a solution in which a solvent is capable of dissolving any more solute at a given temperature. A saturated solution can be defined as a solution in which a solvent is not capable of dissolving any more solute at a given temperature. SOLUBILITY pertains to the maximum amount of solute dissolved in a given amount of solvent at a specific temperature and pressure. Factors affecting Solubility 1. Nature of Solute and Solvent For the solute to be soluble in a given solvent, they must have a similar intermolecular force. “Like disolves Like”