Solutions, Suspensions and Colloids A Matter of Fact Solutions, Suspensions and Colloids

What is a Mixture? Mixtures – two or more substances that are not chemically combined with each other and can be separated by physical means. The substances in a mixture retain their individual properties. Two types: Heterogeneous Mixtures (cereal, salad) Homogeneous Mixture (paint) Mixtures classified based on how well they are mied. Heterogeneous Mixtures – substances in which components are not evenly mixed. Not chemically combined. Ex: oil and vinegar salad dressing, salad, nut cereal. Homogenous Mixtures – substances in which components are evenly mixed Ex: paint, milk – chemically same thoroughout, toothpaste, perfume

Two types of Mixtures Mixtures Homogeneous Mixtures Heterogeneous Mixtures Solutions Colloids Alloys Suspensions

Solutions A type of homogeneous mixture formed when one substance dissolves in another. It is the best mixed of all mixtures. Same appearance and properties throughout The particles are very small, never settle out,nnor can they be filtered out of these mixtures. The particles don’t scatter light.

Solvent and Solute A solution always has a substance that is dissolved and a substance that does the dissolving. Solute -substance that is dissolved Solvent -substance that does the dissolving Lemonade drink mix (solute) and the water (solvent) http://www.chem4kids.com/files/matter_solution.html

Animation of NaCl dissolving in H2O Dissolving a Salt.swf

Solutes Insoluble: Unable to dissolve in the solvent Soluble: Able to dissolve in the solvent

The Universal Solvent: Water www.freeze.com/Content/Item.aspx?pid=1380

Water as a Solvent Many liquid solutions contain water as the solvent. Ocean water is basically a water solution that contains many salts. Body fluids are also water solutions.

Concentration of a Solution Concentration is a measure of how much solute is dissolved in the solvent. Concentrated Orange Juice Concentrated Laundry Detergent Opposite of concentrated is dilute.

Solubility The amount of solute that can dissolve in a given amount of solvent. Example: What happens if you add a lot of sugar to a glass of iced tea? Solubility of solids in liquids increases with temperature. You can add more sugar to hot tea than iced tea. Solubility of gases in liquids decreases with temperature. You can keep more bubbles in cold soda than warm soda. Taking our lemonade, if we add too much sugar to the lemonade, it may not all dissolve. Maximum amount of solute.

Speed up Dissolving? Mixing Heating Crushing Smaller particles dissolve faster. Temperature increase, more easier to dissolve the solute.

Movie on solubility, solute, and solutions.

Solutions are made from solutes and solvents from all states of matter Solutions are made from solutes and solvents from all states of matter. Example: Air is a solution of oxygen and other gases (solutes) dissolved in nitrogen (solvent). All solutions do not have to be like the salt water or lemonade. It can be air too -> gas in a gas.

Types of solutions Solute Solvent Example Gas Gas Air (oxygen in nitrogen) Gas Liquid Soda water (CO2 in H2O) Solid Liquid Ocean water (salt in water) Solid Solid Gold jewelry (copper in gold), brass, bronze, pewter, solder Solutions do not have to be a solid and a liquid. It can be any combination of gas in a gas or gas in a liquid, or liquid in a liquid, or solid in liquid and solid in a solid (alloy)

Types of Solutions Solute Solvent Example Liquid Gas Humid Air Liquid Liquid Antifreeze ethylene glycol in H2O Liquid Solid Dental fillings Hg in Ag Solid Gas Soot, dust in air

Metals dissolved in metals are called alloys. Special solution in which metal dissolved in a metal- pewter, gold jewelery etc. Stainless steel is a mixture of iron and chromium. Brass is an alloy of copper and zinc.

Movie on alloys

Suspensions Suspensions are mixtures containing large particles. If you shake or stir a suspension, the particles will disperse, but will eventually settle out or separate. Particles of a suspension will scatter light. Heterogeneous mixture in which some particles settle out. Snow globe. Particles are insoluble (do not dissolve) Examples: muddy water, salad dressing, snowglobe. Particles scatter light. Like in medicines -> need to shake well. Can sepearate using filter, the larger particles stay.

Colloids Colloids are mixtures containing relatively large particles that do not settle out. The particles are dispersed throughout the mixture, but are not dissolved. Particles of a colloid will scatter light. Ex: Shaving, fog and smoke, gelatin. Light can pass through it and light can be seen Cannot be separated by filtration. (like a solution)

Types of Colloids Gas Liquid FOAMS, whipped cream, mousse Liquid            Gas                FOG, Clouds Liquid            Liquid            EMULSIONS: Mayonnaise,oil,vinegar,egg yolk Liquid            Solid              butter and other gels Solid              Gas               SMOKES, all kinds Solid              Liquid           SOLS, Paint pigment -many are metallic - in H2O or oil Gas Solid Marshmallows  

Separation Techniques Magnets – based on magnetism of the matter Centrifugation – based on densities of the matter Ex: blood is broken down into red blood cells, platelets, plasma

Chromotography Means “Color Writing” It involves passing a mixture dissolved in a mobile phase through a stationary phase. Components travel at different speeds based on their size and therefore separate along the way.

Separation Techniques The Distillation Process Distillation is a process used to separate a mixture into components based on boiling points Involves a change of state, usually from liquid to gas, and then condensation to return the now separated component to liquid state. The distillation apparatus (still) has three parts: (1) A flask with an outlet tube, (2) A condenser, and (3) A vessel.

Distillation Figure 1.13 A simple apparatus for the separation of a sodium chloride solution (salt water) into its components. Boiling the solution evaporates the water, which is condensed, then collected in the receiving flask. After all the water has boiled away, pure sodium chloride remains in the boiling flask.