Larger surface area and more contact area between

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Larger surface area and more contact area between molecules increase strength of force Properties of Water: o Liquid water expands upon freezing The water molecules slow down and form a more spread out, solid lattice In the lattice, each water molecule is farther apart than in a liquid This is why: Ice cubes float because they are less dense than liquid water Water bottles and soda cans explode in the freezer Snowflakes have hexagonal shapes Phases of Matter: o Solid: Particles are very close Fixed volume Definite shape o Liquid: Particles farther apart Fixed volume Indefinite shape o Gas: Particles are independent and far apart Expand to completely fill the container Easily compressible o One of the contributing factors to phase change is temperature Higher temperature = molecules have faster speed and more KE Lower temperature = molecules have slower speed and less KE o The phase of matter (solid, liquid, gas) depends on the strength of the intermolecular forces and how much the heat (temperature and KE) can overcome it Pressure plays a role too
CHEM 113 EXAM 4 Critical Temperature (Tc) o The highest temperature which a distinct liquid phase can exist o Weaker IM forces = lower critical temperature Critical Pressure (Pc) o Pressure required to liquefy a gas at the critical temperature Phase Diagram: o Temperature vs. pressure plot that summarizes the conditions under which the different phases of matter occur o Regions: Critical Point (point B): Critical temperature and critical pressure Beyond this point is a supercritical fluid o Has properties of liquid and gases simultaneously Triple Point (point A): Solid, liquid, and gas all present in equilibrium Solution: o Homogenous mixture of two or more substances o Solvent: Substance present in greatest amount If the solvent is water, we call this solution aqueous o Solute: Substance present in lesser amount Steps in a solution formation: o EX: KCl (a soluble ionic compound) dissolving in water o Step 1: Solute separation KCL is broken apart into K and Cl ions o Step 2: Solvent separation Solvent (water) molecules separate from each other o Step 3: Solvation K and Cl ions are attracted to the delta minus and delta plus charges on the water molecules by ion-dipole forces If the solvent is water, we call this step hydration o Steps 1-3 occur simultaneously Energetics of steps 1-3: o Step 1: Breaking ionic bonds Requires energy Delta H > 0 o Step 2: Breaking IM forces (H-bonds)
CHEM 113 EXAM 4 Requires energy Delta H >0 o Step 3: Forming ion-dipole forces Releases energy Delta H <0 o

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