Solutions, Suspensions Colloids

Solutions Appears to be a single substance but really two or more substances dissolved in a solvent and evenly distributed Very small particles that never settle out Homogeneous

Examples of Solutions Alloys – solid solutions of metals or non-metals dissolved in metals Iced tea, salt water, soda, gasoline

Solute versus Solvent A solute is the substance in a solution that gets dissolved A solvent is the substance in a solution that does the dissolving If something is soluble, the solute can be dissolved in a particular solvent If something is insoluble, the solute will not be dissolved in a particular solvent Solutes can be soluble in some solvents but insoluble in others

Concentration The comparison of solute to solvent When there is not a lot of solute compared to solvent, the solution is dilute When there is a lot of solute compared to solvent, the solution is concentrated

Saturated Solutions Saturated solution – contains all of the solute it can hold at a given temperature. If you add even one more molecule of the solute, it will fall out of solution and rest on the bottom

Unsaturated Solutions Contains less solute than it can hold at a given temperature Can add more solute and it wont fall out of the solution

Supersaturated Solution Solution that holds more than it usually would at a given temperature

Solubility The amount of solute needed to make a saturated solution in a given solvent at a given temperature For solid solute in liquid solvent – solubility rises as temperature rises. For gas solute in a liquid solvent – solubility lowers as temperature rises ex – soda goes flat at warm temperatures

Solubility Table LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World, 1996, page 517 images.hboys2011.multiply.multiplycontent.com/.../SOLUBILITY%20CURVE%202.ppt? Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 gases solids

How to determine the solubility of a given substance? Find out the mass of solute needed to make a saturated solution in 100 cm 3 of water for a specific temperature(referred to as the solubility). This is repeated for each of the temperatures from 0ºC to 100ºC. The data is then plotted on a temperature/solubility graph,and the points are connected. These connected points are called a solubility curve.

How to use a solubility graph? A.IDENTIFYING A SUBSTANCE ( given the solubility in g/100 cm 3 of water and the temperature) Look for the intersection of the solubility and temperature.

What substance has a solubility of 90 g/100 cm 3 of water at a temperature of 25ºC ? Example:

What substance has a solubility of 200 g/100 cm 3 of water at a temperature of 90ºC ?

B.Look for the temperature or solubility Locate the solubility curve needed and see for a given temperature, which solubility it lines up with and visa versa.

What is the solubility of potassium nitrate at 80ºC ?

At what temperature will sodium nitrate have a solubility of 95 g/100 cm 3 ?

At what temperature will potassium iodide have a solubility of 230 g/100 cm 3 ?

What is the solubility of sodium chloride at 25ºC in 150 cm 3 of water ? From the solubility graph we see that sodium chlorides solubility is 36 g.

C. Determine if a solution is saturated,unsaturated,or supersaturated. If the solubility for a given substance places it anywhere on it's solubility curve it is saturated. If it lies above the solubility curve, then it's supersaturated, If it lies below the solubility curve it's an unsaturated solution. Remember though, if the volume of water isn't 100 cm 3 to use a proportion first as shown above.

ToTo Sol. ToTo Solids dissolved in liquids Gases dissolved in liquids As T o, solubility

Sometimes you'll need to determine how much additional solute needs to be added to a unsaturated solution in order to make it saturated. For example,30 grams of potassium nitrate has been added to 100 cm 3 of water at a temperature of 50ºC.

How many additional grams of solute must be added in order to make it saturated? From the graph you can see that the solubility for potassium nitrate at 50ºC is 84 grams

If there are already 30 grams of solute in the solution, all you need to get to 84 grams is 54 more grams ( 84g-30g )

Classify as unsaturated, saturated, or supersaturated. per 100 g H 2 O 80 g NaNO 30 o C 45 g 60 o C 50 g NH 10 o C 70 g NH 4 70 o C =unsaturated =saturated =unsaturated =supersaturated Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 gases solids LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World, 1996, page 517 images.hboys2011.multiply.multiplycontent.com/.../SOLUBILITY%20CURVE%202.ppt?...

Methods to speed up dissolving Crushing a solute increases the surface area of the solute allowing more solvent to surround it thus dissolving it faster Ex. Putting butter in macaroni and cheese Heating a solution increases the energy of the molecules making them move more quickly thus spreading the solute throughout the solvent and speeding up the rate at which the solute dissolves Ex- cooking iced tea Mixing has the same effect as heating does Ex- making chocolate milk

Suspensions A suspension is a mixture in which particles of material are dispersed throughout a liquid or gas and are large enough to settle out The particles are insoluble Heterogeneous mixtures Ex snow globe

Colloids Have properties of both solutions and suspensions Particles in a colloid are much smaller than particles in a suspension Colloids have the same definition as suspensions in that a colloid is a mixture in which particles of material are dispersed throughout a liquid or gas, but the particles of a colloid are not large enough to settle out Particles in a colloid scatter light Ex milk, fog, jello