Solutions

 A homogeneous (uniform) mixture that contains a solvent and at least one solute  Solvent = dissolves the other substances (Ex. water)  Solute = dissolved by the solvent (Ex. salt)  *In solutions, there is more solvent than solute.

 Water is the universal solvent  It dissolves more solutes than any other solvents  Because its polar (slightly charged)  Life depends on water solutions  Water is the solvent in blood, saliva, sweat, tears

 Solutions can be formed from any combination of solids, liquids, and gases.

 Not all mixtures are solutions. Colloids and suspensions are mixtures that have different properties than solutions.

 When a solution forms, particles of the solvent surround and separate the particles of the solute.  Ionic compounds, like salt (NaCl), are separated into individual ions  Covalent compounds (molecular compounds), like sugar, are separated into individual molecules

 Ionic compounds in water conduct electrical current due to the charged ions present  Molecular compounds in water usually do not conduct electrical current

Solutes lower the freezing point of a solvent.  This is why salt is added to icy roads; it melts the ice and keeps it from refreezing thus making the roads less slippery. Solutes raise the boiling point of a solvent.  This is why salt is added to water when boiling pasta; it makes the water hotter thus cooking the pasta faster.

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 Concentrated solutions have a lot of solute in the solvent  Dilute solutions have a small amount of solute in the solvent

 To calculate the concentration of a solution, compare the amount of solute to the amount of solution and multiply by 100 percent.  For example, if a solution contains 10 grams of solute dissolved in 100 grams of solution, then its concentration can be reported as 10 percent.

 Practice Problem  A solution contains 12 grams of solute dissolved in 36 grams of solution. What is the concentration of the solution?  33%

 Solubility is a measure of how much solute can dissolve in a solvent at a given temperature.  If solute continues to dissolve, the solution is unsaturated.  If no more solute will dissolve, the solution is saturated. Which compound is the most soluble?

 The solubility of the compound potassium nitrate (KNO 3 ) varies in water at different temperatures.

 Reading Graphs:  At which temperature shown in the graph is KNO 3 least soluble in water?  KNO 3 is least soluble at 0ºC.

 Reading Graphs:  At which temperature shown in the graph is KNO 3 least soluble in water?  KNO 3 is least soluble at 0ºC.

 Calculating:  About how much more soluble is KNO 3 at 40ºC than at 20ºC?  KNO 3 is about twice as soluble at 40ºC as it is at 20ºC.

 Interpreting Data:  Does solubility increase at the same rate with every 20ºC increase in temperature? Explain.  No; the curve shows that solubility increases more with each 20ºC increase in temperature.

 Pressure- increases solubility (soda can)  Solvent- some solvents and solutes are not compatible (oil and water), “like dissolves like”  Temperature- increases solubility (high temps when cooking)

 ACIDS  Properties: Sour Taste, Corrosive (reacts with metals), Reacts with carbonates to make CO2 gas, Turns blue litmus paper red  BASES  Properties: Bitter taste, Slippery Feel, Turns red litmus paper blue (“Bases turn Blue”)

Acids:  Examples: Juice, Vitamin C, Vinegar, HCl Bases:  Examples: Ammonia (cleaners), baking soda, soap

 Acids in Solutions  An acid produces Hydrogen ions (H+) in water  Acids in water solution separate into hydrogen ions (H+) and negative ions. In the case of hydrochloric acid, for example, hydrogen ions and chloride ions form:  High in Hydrogen Ions (H+), Low in Hydroxide Ions (OH-)  Low on the pH scale (pH0-pH7) *pH7= neutral  Bases in Solutions  A base produces hydroxide ions (OH-) in water  When bases dissolve in water, the positive ions and hydroxide ions separate. Look at what happens to sodium hydroxide in water:  Not all bases contain hydroxide ions. For example, the gas ammonia (NH3) does not. But in solution, ammonia is a base that reacts with water to form hydroxide ions.  Low in Hydrogen ions (H+), High in Hydroxide Ions (OH-)  High on pH scale (ph7-pH14)

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