Presentation on theme: "Monday, November 28, 2011 Sit. Materials out. Backpack in drawer. Silence. Do Now: first, put your workbooks on the desk, open to p. 204, so I can check."— Presentation transcript:
Monday, November 28, 2011 Sit. Materials out. Backpack in drawer. Silence. Do Now: first, put your workbooks on the desk, open to p. 204, so I can check your homework. Then copy down today’s homework from the agenda board..
Today’s Goals After today: In a real-life situation (such as in your kitchen or bathroom), you will be able to judge how best to dissolve something in order to clean up a mess or improve your food. To achieve this, you will: Learn what solvents dissolve what solutes and why Learn how to decide what kind of solute you’ve got Learn what factors affect how quickly solutes dissolve
Remember from last week: A substance dissolves in a solvent by separating into its smallest particles (That’s IONS or MOLECULES) Intermolecular forces hold a liquid solution together
Factors affecting solubility, or What makes something dissolve or not? Remember: a solute dissolves if its particles are more attracted to the solvent than to each other. Remember: molecules are polar or nonpolar Remember: we say a solute is soluble or insoluble in a given solvent. Being soluble is not all or nothing Different solutes dissolve different amounts in a solvent For a given solvent and solute, solubility can be changed
The #1 solubility factor is… Like dissolves like.
“Like Dissolves Like” Fats Fats dry cleaning fluid dry cleaning fluid Greases Greases turpentine turpentine Waxes Waxes gasoline gasoline Polar and ionic solutes dissolve best in polar solvents Nonpolar solutes dissolve best in nonpolar solvents Inorganic Salts Water Water Sugars Sugars Small alcohols Small alcohols Acetic acid Acetic acidAmmonia
Polar and nonpolar don’t dissolve … But you can use science to help. Soap/detergent molecules have a polar end and a nonpolar end. The nonpolar end dissolves grease The polar end dissolves in water You can clean with vinegar, ammonia, and dish soap in spray bottles
Nonpolar dirt – greasy, oily In the kitchen: sprayed-on vinegar cleans up grease, tables, walls, doors, floors, windows…. Evaporates completely disinfects In the bathroom: Bartender’s Friend (Home Depot) is a stronger acid (wear gloves) that doesn’t use bleach (still disinfects)
More help from science: polar Most colored compounds dissolve in polar solvents Not all ionic compounds dissolve well in water – but they often dissolve in acetic acid (vinegar) or ammonia solution (basic) Others dissolve in other polar solvents (rubbing alcohol, acetone) If one doesn’t work, TRY ANOTHER (Google is your friend here!)
A little lab activity here! And some terms: Solubility: the amount of solute that will dissolve in a given solvent at a given temperature Saturated: the solution contains all the solute it can hold at that temperature. If undissolved solid remains in the solution after significant time has passed, it’s probably saturated. Unsaturated: the solution can dissolve more solute Supersaturated: the solution contains MORE solute than it wants to dissolve at that temperature – usually made by making a hot saturated solution and cooling it.
Solubility Trends (More Factors) 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.
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
Exit Slip—No more talking at this time. Put away all your materials except a pencil and today’s notes. You will receive a sheet with several situations you might encounter at home. Use what you’ve learned today to decide how to deal with each.