WATER And Solution Formation Ch. 15 & 16 WATER And Solution Formation

Water is unique Polar Molecular Compound IMF = Hydrogen “bonds” = VERY STRONG Causes : High boiling point Low vapor pressure High surface tension Surfactant: disrupts H-bond, lowers surface tension

Solid Water (ICE) Unique structure due to H-bond Ice floats bc of structure Less dense than liquid Open hexagon structure or honeycombed shape

Solutions Solvent: Dissolving medium (does the dissolving) Solute: the dissolved particles (gets dissolved) Solvation: the dissolving process “like dissolves like” Water is called the UNIVERSAL SOLVENT

Electrolytes Electrolyte: conducts electricity when dissolved in water All ionic compounds are electrolytes Dissociate into ions.

Nonelectrolytes Nonelectrolyte: doesn’t conduct electricity Most molecular compounds Especially carbon based (organic) compounds

Solutions Notes

Properties of Liquids Both Gases and liquids have kinetic energy This means the molecules are constantly moving Key difference: Gases have no intermolecular forces Liquids do!

Evaporation vs. Vaporization Vaporization: phase change from liquid to gas when the liquid is boiling Evaporation: phase change from liquid to gas when liquid is not boiling Happens at the surface because the KE of the molecules is greater so they become gases.

Boiling Point Temperature where a liquid begins to boil and vaporize. Happens when the vapor pressure of the liquid is equal to the external pressure. When pressure decreases boiling point decreases This is why water boils faster at higher altitudes- increase in altitude = decrease in pressure

Intermolecular Forces Review Forces between molecules in a compound Weaker than ionic and covalent bonds Hydrogen bonding is strongest, Van der wals are weakest.

Properties of Water Water molecules are polar (unequal distribution of charge!) Oxygen atoms have slightly negative charge Hydrogen atoms have slightly positive charge Hydrogen bonding gives water unique properties of high surface tension and low vapor pressure.

Two types of mixtures Homogeneous: mixtures with uniform properties throughout Heterogeneous: mixtures that have two or more components or phases Solution: A homogeneous mixture of two or more substances in a single phase.

What happens when sugar dissolves? Sugar molecules get distributed uniformly among the water molecules.

What does it mean to be soluble? Soluble- capable of being dissolved Is sugar soluble in water? What about oil? Like dissolves like! (oil is nonpolar, water is polar)

Parts of a solution Solute: the substance that is being dissolved (sugar, salt, hot chocolate mix) Solvent: the substance that is having something dissolved into it (usually water). Also called the dissolving medium Usually more solvent than solute in a solution

Types of solutions Solutions can be in each of the three phases of matter: solid, liquid gas! Ex: 14 karat and 18 karat gold are solutions.

Properties of solutes Electrolytes: a substance that dissolves in water and conducts an electric current. Ex: NaCl, or any soluble ionic compound Nonelectrolyte: substance that dissolves in water that does not conduct electric current. Ex: Sugar

Factors that increase the rate of dissolution Dissolution: process of a substance dissolving Increased surface area: dissolving happens at the surface. A sugar cube will dissolve slower than a spoonful of sugar. Agitation: stirring or shaking a solution helps to dissolve the solids faster Heating: as the solvent temp heats up the particles move faster (faster kinetic energy) so they can dissolve faster--for solids!

Solubility Solution equilibrium: the physical state where dissolving and crystalization are happening at the same time Saturated solution: a solution that contains the maximum amount of dissolved solute. (full, can’t take any more) Unsaturated: a solution that contains less solute than a saturated solution (still has room for more)

Solubility Solubility: the amount of a substance required to form a saturated solution with a specific amount of solvent at a specific temperature. Ex: at 20°C exactly 35.9 g of NaCl will dissolve in 100 mL of water.

Solubility Graph and calculation Solubility is determined in grams of solute 100 g of water What is the solubility of sodium nitrate at 20oC? How much ammonium chloride can be dissolved in 200g of water at 30oC? How does gas solubility change with temp?

Solution calculations Molarity (M): moles solute/L soln Molality (m): moles solute/kg solvent M&m problems can be solved by setting up ratios! Percent concentration: mass solute/mass soln ~~~May need to convert between mass and moles~~~