Solutions Applied Chemistry 4.0

Background to Solutions  A solution is a homogenous mixture that has different substances dissolved in it that cannot be seen.  This results in a single physical state.  Parts of a solution Solute: substance that is dissolved … present in smaller amount Solvent: substance that does the dissolving …present in larger amount

Parts of a Solution Solvent Solute Homogeneous Mixture SOLUTION

Properties of Solutions  Small particles  Evenly distributed particles (uniform)  Particles will not separate when at rest  The ability to dissolve (solubility )  Dissolving Salt Animation Dissolving Salt Animation

Background (cont.)  Soluble means something can be dissolved in something else.  Insoluble mean something cannot be dissolved in something else.  Dissolving a solid in a liquid can affect the boiling point and freezing point. This is called a colligative property.

Types of Solutions Solid Solutions  Solid solution – final phase is solid  Alloys: Solid solutions containing two or more metals or a metal and a nonmetal  Advantages of alloys over pure metals: Stronger Cheaper More resistant to corrosion Lighter Harder

Examples of Alloys Brass is an alloy of copper and zinc. Steel is an alloy of carbon and iron. Bronze is an alloy of copper and tin.

A closer look at alloys

Types of Solutions Gaseous and Liquid Solutions  Gaseous Solutions – final phase is gas Ex. Air  Liquid Solutions – final phase is liquid Miscible liquids : Can mix in all proportions (ex. alcohol and water) Immiscible liquids : Cannot mix in all proportions (ex. oil and water)

Miscible Liquids

Immiscible Liquids

Types of Solutions Aqueous Solutions  Solutions with water as the solvent.  Because water can dissolve so many things, it is called the Universal solvent.  Electrolyte – a solution that conducts electricity.

Example of an electrolyte

Other types of solutions  Tincture : Solutions with alcohol as the solvent (ex – herbal medicines)  A saline solution is a solution of salt and water. The solute is salt. The solvent is water.  A dilute solution is a solution with little solute.  A concentrated solution is a solution with a lot of solute.

Concentration  A measure of the amount of solute in a solution.  % Concentration = mass of solute x 100 mass of solution  Usually used for concentrated solutions.

Example: Salt water is prepared by mixing 3g of salt with 97g of water. Calculate % concentration.  Mass of solute:  Mass of solvent:  Mass of solution: (solvent + solute) % Con: 3 g 97 g (water) 100 g 3 x 100 = 3% 100 Dilution : to decrease the concentration by adding more solvent

Parts per million (ppm) -Usually used with dilute solutions.  One hundredor One thousand  One hundredthor One thousandth 1/1001/1000  One million or One billion 1,000,0001,000,000,000  One millionthor One billionth 1/1,000,000 1/1,000,000,000 1 ppm1 ppb

Parts per million  Sea water is a 3% solution.  Means: 3 grams of salt to 100 grams of sea water or 3 parts salt to 100 parts sea water  Looks like: 3/100 dilution (keep as a fraction)

ppm Examples  Food coloring is a 10% aqueous solution.  Means:10 grams of pigment to 100 grams of solution or 10 parts pigment to 100 parts of solution  Looks like: 10/100 dilution or 1/10 dilution

Other examples of ppm & ppb  1 ppm is 1 second in 12 days.  1 ppm is one minute in two years.  1 ppm means 1 penny in $10,000.  1 ppm means one inch in 16 miles.  1 ppb is 1 second in 11,574 days.  1 ppb is one minute in 32 years.  1 ppm means 1 penny in $10,000,000.  1 ppb means one inch in 16,000 miles.

Solubility and the Dissolving Process  Solubility is a physical property that gives the grams of solute that will dissolve in a solvent (usually water) at a given temperature and pressure.  Saturated: A solution is saturated if it contains as much solute as can possibly be dissolved under existing conditions of temperature and pressure.  Unsaturated: Has less solute than the maximum amount that can be dissolved.  Supersaturated: Has more solute than the maximum amount that can be dissolved. Solution Video (G drive)

Unsaturated vs. Saturated Solution

Supersaturated Solutions Supersat Video Sodium Thiosulfate Sodium Acetate Supersat Sodium Acetate (on G drive)

Three Factors Affecting the Rate of Dissolving  Surface Area – increases the number of collisions between the solute and solvent Sugar cube vs. sugar crystals  Stirring – increases the number of collisions between the solute and solvent. Stirring sugar in coffee/tea  Temperature – increases the energy of the collisions between the solute and solvent. Warm water vs. cold water

Saturated sol’n Supersaturated solution Unsaturated solution At 20 o C, a saturated solution contains how many grams of NaNO 3 in 100 g of water? What is the solubility at 70 o C? 135 g/100 g water What kind of solution is formed when 90 g NaNO 3 is dissolved in 100 g water at 30 o C? unsaturated What kind of solution is formed when 120 g NaNO 3 is dissolved in 100 g water at 40 o C? supersaturated 90 g

At 20°C, a saturated solution contains how many grams of NaNO 3 in 100 g of water? What is the solubility at 70 o C? What kind of solution is formed when 90 g NaNO 3 is dissolved in 100 g water at 30 o C? What kind of solution is formed when 120 g NaNO 3 is dissolved in 100 g water at 40 o C?