Section 1: Solutions and Molarity

Solutions Solutions are homogeneous mixtures The substance you have more of is the solvent (the substance that you are dissolving a material IN) The substance you have less of is the solute (the material you are trying to dissolve) Solutions can be liquid (soda), solid (brass), or gas (air)

Particles in Liquids Atoms/Molecules in liquids are spread farther apart than in solids. This allows them to dissolve (fit) other particles between the atoms/molecules.

Concentration The amount of solute present in the solvent. Example: Kool-Aid can be as diluted or as concentrated as you want it to be, just add more water (solvent) to dilute the drink Concentration is represented by the symbol [ ] The wrong concentration can cause an object to work improperly or be harmful to living things Example: Eye drops for humans can be harmful for a canine because of the different concentration requirements

Properties of Solutions The boiling point of a liquid increases when molecules of a solute are added (has to get hotter to boil) Solute molecules block the surface of the solution (location where it would boil/evaporate) When a solute is dissolved, the freezing point is lowered (a lower temperature must be reached to freeze the solution) Solute molecules block the solvent molecules from freezing together and crystallizing

Saturation When the solute and solvent are put together, there is a limit to how much solute can be dissolved Unsaturated solution: more of the solute can be dissolved Saturated solution: no more solute will dissolve Supersaturated solution: an unstable and temporary situation where solution contains more dissolved solute than it normally would Occurs when there is a Δ in temperature, volume, or pressure

Molarity (M)  Symbol Used to calculate the concentration of a solution. The number of moles of solute per liter of solution M = moles liter

Molarity Example #1 What is the molarity of a solution made by dissolving 0.3 mole of Ca(NO 3 ) 2 in enough water to make 5 L of solution? M = moles liter = 0.3 mol 5 liter = 0.06 M Ca(NO 3 ) 2

Molarity Example #2 How many liters of 0.5 M NaCl solution can be made from 0.1 mole of NaCl? M = moles liter 0.5 M = 0.1 mole x liters 0.5x = 0.1 x = 0.2 L NaCl solution