Presentation on theme: "Classification of Matter Solutions Solutions are homogeneous mixtures."— Presentation transcript:
Classification of Matter Solutions Solutions are homogeneous mixtures
Solute A solute is the dissolved substance in a solution. A solvent is the dissolving medium in a solution. Solvent Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Water in salt waterWater in soda
If less than one gram of the substance will dissolve in 100 grams (or 100 mL) of solvent, the substance is considered insoluble. If more than ten grams of substance will dissolve in 100 grams (or 100 mL) of solvent, the substance is considered soluble. If between one and ten grams of a substance will dissolve in 100 grams (or 100 mL) of solvent, the substance is considered moderately soluble.
“Like Dissolves Like” Fats Fats Benzene Benzene Steroids Steroids Hexane Hexane Waxes Waxes Toluene Toluene Inorganic Salts Water Water Sugars Sugars Small alcohols Small alcohols Acetic acid Acetic acid Polar and ionic solutes dissolve best in polar solvents Nonpolar solutes dissolve best in nonpolar solvents
The polar charges on water molecules are attracted to the opposite charge on the ions in ionic compounds If this attraction causes the ions to separate (“dissociate”), then the ionic compound “dissolves” Ionic compounds that are soluble, always form ions in solution
K 2 CrO 4 (aq) + Ba(NO 3 ) 2 (aq)
Solubility of NaCl in Water
An electrolyte is: A substance whose aqueous solution conducts an electric current Ionic compounds form electrolytes when they dissolve, because the ions separate and move around independently A nonelectrolyte is: A substance whose aqueous solution does not conduct an electric current Molecular compounds do not form electrolytes when they dissolve Electrolytes and Nonelectrolytes
Electrolytes vs. Nonelectrolytes
Solubility of Molecular Compounds in Water If we are comparing the water solubility of two similar molecules, the one with the higher percentage of the molecule that is polar (hydrophilic) is expected to have higher water solubility. We predict that the molecule with the higher percentage of its structure that is nonpolar (hydrophobic) to be less soluble in water.
Hydrophobic and Hydrophilic
Triglycerides (Fats and Oils)
Tristearin –Line Drawing
Soap and Detergent
Cleaning Greasy Dishes
Oil Droplets and Soap or Detergent
Solubility Trends The solubility of MOST solids increases with temperature. The rate at which solids dissolve increases with increasing surface area of the solid. The solubility of gases decreases with increases in temperature. The solubility of gases increases with the pressure above the solution.
Using Coffee… Cold Warm Hot Cold Warm Hot Water Water Water Water Water Water
Solubility and Temperature Temperature affects how much solute dissolves (solubility) Temperature affects how quickly a solute dissolves (rate) Increasing the temperature not only increases the amount of solute that will dissolve but also increases the rate at which the solute will dissolve
Therefore… Solids tend to dissolve best when: o Heated o Stirred o Ground into small particles Gases tend to dissolve best when: o The solution is cold o Pressure is high