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. WHAT IS A SOLUTION?

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 WATER

BUT WATER IS NOT THE ONLY SOLVENT…

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. COLLOIDS AND SUSPENSIONS

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. PARTICLES IN A SOLUTION

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

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. The salt(solute) makes it harder for water(solvent) to form ice crystals. 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. EFFECTS OF SOLUTES ON SOLVENTS

SOLUTIONS SONG

Dilute solutions have a small amount of solute in the solvent (Unsaturated) Adding more solute to the solution makes the solution become a more concentrated solution. Concentrated solutions have a lot of solute in the solvent (Saturated) When there is so much solute in a solvent that the solvent can’t contain it at a given temperature, the solution is called a supersaturated solution. Increasing the temperature will allow the solvent to “hold” more solute. CONCENTRATION

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. CALCULATING A CONCENTRATION

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

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. SOLUBILITY Which compound is the most soluble?

TEMPERATURE AND SOLUBILITY 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. TEMPERATURE AND SOLUBILITY

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

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. TEMPERATURE AND SOLUBILITY

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. TEMPERATURE AND SOLUBILITY

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) FACTORS THAT AFFECT SOLUBILITY: