Module 6 Portage Learning Chemistry Questions And Answers 2023

Module 6 Portage Learning Chemistry Questions And Answers 2023 Amorphous solids Ans- particles are arranged in a random fashion Colligative properties Ans- physical properties of solvents that are dependent on the concentration of the solute present and the identity of the solvent but not on the identity of the solute. They include vapor pressure, freezing point and boiling point Colloids Ans- heterogeneous mixtures which appear to homogeneous one-phase mixtures but are actually composed of particles too small to be seen with the naked eye Condensation Ans- process of gas being converted to liquid Critical point Ans- the temperature above which a substance cannot exist in the liquid phase Critical pressure Ans- the lowest pressure required for the substance to exist as a liquid at the critical point Crystalline solids Ans- particles are arranged in one of several different orderly, repeating, geometric patterns Electrolytes Ans- ionic or very polar compounds which dissolve to form solutions of ions which conduct an electric current Fluids Ans- substances like liquids and gases which have no fixed shape and so they flow Ionization Ans- the splitting of molecules to form ions Molality Ans- the number of moles of solute present per kilogram of solvent Molarity Ans- the number of moles of solute present per liter of solution Nonelectrolytes Ans- compounds which dissolve to form solutions of molecules which do not conduct an electric current Phase Ans- any state of matter such as solid, liquid or gas Strong electrolytes Ans- solutes that ionize completely Sublimation Ans- the conversion of a solid directly to the gas state Surface tension Ans- the force that causes a liquid which is in contact with a gas like air to assume a shape that has the least amount of surface area causing the surface to act like a thin elastic sheet Triple point Ans- the temperature and pressure at which the solid, liquid and gas phases can coexist Vapor pressure Ans- pressure exerted by vapor molecules above a liquid Weak electrolytes Ans- solutes that only partially ionize Why are liquids the least common state of matter? Ans- they can exist only within a relatively narrow range of temperatures and pressures Differentiate between evaporation and vaporization Ans- Vaporization is the conversion of liquid particles to vapor at the boiling point temperature of the material. The process of liquid converting to vapor molecules can also take place in a very limited manner at temperatures lower than the boiling point and is called evaporation Differentiate between a crystal lattice and a unit cell Ans- A crystal lattice is the orderly, repeating geometric pattern in which the particles of a crystalline solid are arranged. The unit cell is the smallest section of the crystal lattice having that arrangement of particles Why does a phase change occur at one temperature rather than over a temperature range? Ans- During a phase change, the temperature of the material remains constant as all of the energy being added is being used to overcome forces of attraction between the particles and separate them so the temperature does not rise. Over any other portions of the temperature range, when a material is heated, the temperature of the material will rise as the energy added causes the molecules to move faster and demonstrate a higher temperature, which is really a measure of the kinetic energy of the molecules Why does diffusion take place quickly in a gas, more slowly in a liquid and not at all in a solid? AnsDiffusion is the non-energy-requiring movement of particles from regions of higher concentration to regions of lower concentration. Diffusion in a liquid occurs more slowly than in a gas since the gas particles are moving more rapidly. Solids do not show the property of diffusion since the particles in a solid can only vibrate around a fixed point rather than move throughout the sample. Explain water's concave meniscus in terms of cohesive and adhesive forces Ans- Cohesive forces are the attractions between particles of the same type, such as the bonds between water molecules whereas adhesive forces are attractions between a particle of one type and particles of a different type, such as the bonds between water molecule and those of its glass container. These cohesive and adhesive forces combine to cause liquids to form a meniscus (curved surface) in a glass tube. A liquid with strong cohesive forces, such as water, tries to roll itself into a ball to minimize surface tension, but water is also attracted to the walls of any tube by adhesive forces, causing the water to form a concave meniscus. Explain the difference in the properties of graphite and diamond which are both pure carbon Ans- In graphite the atoms are arranged in planes which can slide relative to one another making graphite a good solid lubricant. In diamond the atoms are arranged in tetrahedrons which are tightly bonded together making carbon the hardest substance known. Explain why the vapor pressure of a liquid increases with increasing temperature Ans- Water molecules in the liquid state freely vibrate and rotate. As the temperature rises, the vibrations and rotations become intense enough to overcome the forces that keep the molecules together. The molecules begin to undergo translational motion allowing the molecules to convert to the vapor state and these exert a pressure above the still-existing liquid molecules called the vapor pressure of the substance. Higher temperature = greater conversion to vapor = higher vapor pressure Why is liquid water more dense than ice? Ans- Ice has empty spaces between the molecules in its structure as compared to liquid water List and describe the two components of a solution Ans- The minor component of a solution which is being dissolved is called the solute while the major component doing the dissolving is called the solvent. Describe/define the Tyndall effect Ans- Colloids can be distinguished from solutions by use of a beam of light which is scattered by colloids but passes un-scattered through a solution, a result known as the Tyndall effect Explain why sugar can be made to dissolve more quickly by grinding it to a fine crystal Ans- Grinding sugar to a fine crystal increases the surface area of the crystal and this makes it dissolve more quickly because solute particles dissolve by leaving the surface of their bulk structure which is in contact with the solvent What rule is used to predict the solubility of materials? Ans- The "like dissolves like" rule is used to predict the solubility of materials with polar solvents only dissolving polar (and ionic) substances and nonpolar solvents only dissolving nonpolar substances. Why does a bottle of soda pop "fizz" when it is opened? Ans- When a bottle of soda pop is opened, the pressure above the solution decreases and some of the carbon dioxide bubbles off since a lower pressure allows the gas molecules in the solution to escape Why does a temperature increase usually increase the solubility of a solid? Ans- Dissolving most solids is an endothermic process; doing so absorbs heat. Adding heat (by increasing the temperature of a solution) causes any dissolving process to change in the direction that consumes the added energy. For a solid or liquid, heat is absorbed as the solute dissolves in water (heat of solution is endothermic, requiring energy) so a solid or liquid is more soluble at a higher temperature Explain how and why the presence of a solute affects the vapor pressure of a solvent Ans- The presence of a solute lowers the vapor pressure of a solvent because some of the solute particles occupy the space near the surface of the liquid replacing some of the solvent particles thereby decreasing the rate at which solvent particles can enter the vapo