Mixtures and Solutions

Mixtures, elements, compounds Scientists like to classify things. One way that scientists classify matter is by its composition. Based on composition, matter can be classified into: Elements, Compounds, and Mixtures.

By asking these questions scientists can classify matter into: Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means. Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means. Mixtures – two or more substances that are in the same place, but their atoms are not chemically combined and can be separated by physical means. The substances in a mixture retain their individual properties. Solutions – a special kind of mixture where one substance dissolves in another.

Mixtures A mixture is a combination of two or more components that are NOT chemically combined, and retain their identities. Mixtures can be physically separated. The identities of the substances DO NOT change in a mixture.

Mixtures When a mixture’s components are easily recognizable, such as pizza, it is called a heterogeneous mixture. Example: Suspensions In a homogeneous mixture such as chocolate milk, the component particles cannot be distinguished, even though they still retain their original properties. Example: Colloids and Solutions

Homogeneous Mixtures A mixture that appears to be the same throughout. It is “well mixed.” The particles that make up the mixture are very small and not easily recognizable. Homogeneous mixtures can be solutions or colloids.

Examples of heterogeneous mixtures Sand and pebbles Oil and water Powdered iron and powdered sulfur

Heterogeneous Mixtures Mixtures can be solid. Granite is a heterogeneous mixture.

Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures. They are also colloids.

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Types of Mixtures There are three types of mixtures: Suspensions Colloids Solutions

Suspensions A mixture in which particles of a material are dispersed through- out a liquid or gas but are large enough that they settle out. Particles are insoluble, so they DO NOT dissolve in the liquid or gas. Particles can be separated using a filter. Examples: Salad dressing Medicines that say “shake well before use” Animation of the particles in colloid, solutions, and suspensions: http://www.media.pearson.com.au/schools/cw/au_sch_chandler_qs1_1/int/solutions.html

Types of Mixtures There are three types of mixtures: Suspensions Colloids Solutions

Colloids A colloid is a mixture in which the solute is broken down into pieces that are too small to see with the naked eye, but are large enough to interfere with visible light. As a result, colloids are cloudy. In a colloid the particles are mixed together but not dissolved. The particles are relatively large and are kept permanently suspended. The particles are dispersed throughout but are not heavy enough to settle out. Animation of the particles in colloid, solutions, and suspensions: http://www.media.pearson.com.au/schools/cw/au_sch_chandler_qs1_1/int/solutions.html

Colloids - A colloid will not separate upon standing. The particles are not dissolved! The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy. Milk is an emulsified colloid of liquid butterfat globules dispersed within a water-based solution. http://www.dnatube.com/video/1687/Colloid-Particles-under-Brownian-Motion

Types of Mixtures There are three types of mixtures: Suspensions Colloids Solutions

Solutions A solution is a type of homogeneous mixture formed when one substance dissolves in another. A solution always has a substance that is dissolved and a substance that does the dissolving. The substance that is dissolved is the solute and the substance that does the dissolving is the solvent. The particles of the solute separate from each other and become surrounded by particles of the solvent. Animation of Salt dissolving in water: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

Solutions A solution may be liquid, gaseous, or solid. A mixture that appears to be a single substance but is composed of particles of two or more substances that are distributed evenly amongst each other. A solution may be liquid, gaseous, or solid. Examples of solutions Liquid - seawater Gas - air Solid - alloys

Solutions Dissolving – The process in which particles of substances separate and spread evenly amongst each other. Solute – substance that is dissolved. A solute is soluble, or able to dissolve. Solvent – substance in which solute is dissolved. A substance that is insoluble is unable to dissolve, forms a mixture that is not homogeneous, and therefore NOT a solution.

Metals dissolved in metals are called alloys. Types of solutions Solute Solvent Example Gas Air (oxygen in nitrogen) Liquid Soda water (carbon dioxide in water) Solid Ocean water (salt in water) Solid Alloys, Gold jewelry (copper in gold) Metals dissolved in metals are called alloys.

Particles in Mixtures and Pure Substances So, in simplest terms, the difference between solutions, colloids and suspensions is the size of the solute particles. http://abetterchemtext.com/Mixtures/mix_type.htm

How does a solution form?

How does a solution form? A solution forms when particles of the solute separate from each other and become surrounded by particles of the solvent.

How does a solution form? Animation and Video Animation of Salt dissolving in water: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf How Water Dissolves Salt – video – Dissociation of salt - https://www.youtube.com/watch?v=EBfGcTAJF4o

is made of two parts the solvent and the solute Solutions is made of two parts the solvent and the solute www.st-hilds.durham.sch.uk/.../mixture.jpg

is the liquid that does the dissolving. Solvent is the liquid that does the dissolving. www.dkimages.com/.../previews/1052/707770.JPG

the solid that dissolves in the solvent discover.edventures.com/.../s/solute/support.gif

Ocean water is a solution

The universal solvent: Water

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.

Air is a solution of oxygen and other gases dissolved in nitrogen

Alloys – a mixtures of solid metals. Stainless steel is a mixture of iron and chromium. Brass is an alloy of copper and zinc. Bronze is an alloy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals (such as aluminum, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon.

Solutes and Conductivity Ionic compounds in water conduct electric current, but a solution of molecular compounds (neutral) may not. Pages 401

Effects of Solutes Solutes raise the boiling point of a solution above that of the solvent. Page 401 in the book

Effects of Solutes Solutes lower the freezing point of a solution below that of the solvent alone. Page 401 in the book

Techniques for Separating Mixtures Distillation Magnetism Centrifugation Evaporation Filtration Chromatography Decanting

Techniques for Separating Mixtures Distillation - separates a mixture based on boiling points of the components. Examples : saltwater crude oil into gasoline and kerosene Video: https://www.youtube.com/watch?v=xxNfJLMNS4E

Techniques for Separating Mixtures Distillation - http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/oneearth/fuelsrev1.shtml

Techniques for Separating Mixtures Magnetism – Magnetic attraction separates iron or other magnetic materials from non-magnetic objects.

Techniques for Separating Mixtures Centrifugation - spins and separates mixtures according to densities. Centrifuge Process: https://www.youtube.com/watch?v=9CYaPLIX4VM Density Gradient Centrifugation - Isolate Mononuclear Cells from Whole Blood (Ficoll or Lymphoprep) https://www.youtube.com/watch?v=Cl4sTwKFe9k

Techniques for Separating Mixtures Evaporation Separates mixtures by letting some of the components turn into gas, leaving the solid components behind. It can be done quickly with gentle heating or left out to 'dry up' slowly in 'open air'. The solid will almost certainly be less volatile than the solvent and will remain as a crystalline residue. Evaporation is often followed by crystallization.

Techniques for Separating Mixtures Filtration – separates solids from liquids by pouring the mixture through a filter. The solids are collected in the filter, while the liquids go through into another container. Video: https://www.youtube.com/watch?v=Q0s71cjCNWs

Techniques for Separating Mixtures Chromatography separates a mixture of chemicals, which are in gas or liquid form, by letting them creep slowly past another substance, which is typically a liquid or solid Tutorial: Paper and Thin Layer Chromatography | The Chemistry Journey | The Fuse School https://www.youtube.com/watch?v=J8r8hN05xXk CHROMATOGRAPHY: Technique for separating mixtures of products (Animation) https://www.youtube.com/watch?v=0m8bWKHmRMM

Decanting (Decantation) Techniques for Separating Mixtures Decanting (Decantation) a process for the separation of mixtures by removing a layer of liquid, generally one from which a precipitate has settled. The purpose may be either to produce a clean decant, or to remove undesired liquid from the precipitate (or other layers). https://www.youtube.com/watch?v=VIjyNF3s26M

Separating Mixtures Take out your Chapter 11 packet Work on page 395

January 13th, 2016 Do NOW Take your Chapter 11 out (you should have it with you because you tore it out yesterday) Now, do page 395.

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Solubility

Solutes and Conductivity Ionic compounds in water conduct electric current, but a solution of molecular compounds (neutral) may not. Pages 401

Effects of Solutes Solutes raise the boiling point of a solution above that of the solvent. Page 401 in the book

Effects of Solutes Solutes lower the freezing point of a solution below that of the solvent alone. Page 401 in the book

Solubility A measure of how much solute can dissolve in a solvent at a given temperature.

Solubility The solubility - A measure of how much solute can dissolve in a solvent at a given temperature. Solubility is usually expressed in grams of solute per 100 ml of solvent (g/100ml) Can help identify a substance. Three (3) methods that affect solubility Mixing, stirring, or shaking Heating Crushing or grinding (particle size)

Concentration the ratio of solute to solvent woelen.scheikunde.net/.../exp0012.jpg

Concentrated solutions with a high ratio of solid material (solute) to liquid (solvent) (strong) www.global-b2b-network.com/direct/dbimage/502...

Dilute solutions with a low ratio of solid material (solute) to liquid (solvent) woelen.scheikunde.net/.../exp0012.jpg (weak)

Saturated Solution solute dissolves in a solvent until no more will dissolve (additional material may sit at the bottom)  www.bbc.co.uk/.../science/images/sci_dia_26.gif

Factors Affecting Solubility Pressure Type of solvent Temperature Particle size

Factors Affecting Solubility Pressure - As pressure increases the solubility of a gas solute in a liquid solvent increases.

Factors Affecting Solubility Type of solvent For liquid solutions: “like likes like” Ionic and polar compounds usually dissolve in very polar solvents. Nonpolar compounds do not usually dissolve in very polar solvents, but they will dissolve in nonpolar solvents.

Factors Affecting Solubility Temperature - For most solid solutes, solubility increases and temperature increases. - Unlike most solids, the solubility of a gas decreases as temperature increases.

Particles in Mixtures and Pure Substances The diagram shows five particles of elements and compounds. Each circle represents an atom of an element. Match the pictures A to E to the following questions. Diagram (a) Which particle picture represents a mixture of two compounds? ____ (b) Which particle picture represents a pure compound? ____ (c) Which particle picture represents a mixture of an element and a compound? ____ (d) Which particle picture represents a pure element? ____ (e) Which particle picture represents a mixture of two elements? ____ (f) Which particle picture could represent pure water? ____ (g) Which particle picture could represent something dissolved in water? ____ http://www.yenka.com/activities/Substances_and_Mixtures_-_Activity/

Particles in Mixtures and Pure Substances So, in simplest terms, the difference between solutions, colloids and suspensions is the size of the solute particles. http://abetterchemtext.com/Mixtures/mix_type.htm

Particles in Mixtures and Pure Substances http://www.sciencequiz.net/jcscience/jcchemistry/elements_compounds/elements01.htm http://www.elmhurst.edu/~chm/vchembook/171solublesalts.html http://www.bbc.co.uk/bitesize/ks3/science/chemical_material_behaviour/compounds_mixtures/activity/ Methods for separating Mixtures: http://www.bbc.co.uk/bitesize/ks3/science/chemical_material_behaviour/compounds_mixtures/revision/9/ Animation of the particles in colloid, solutions, and suspensions: http://www.media.pearson.com.au/schools/cw/au_sch_chandler_qs1_1/int/solutions.html

Particles in Mixtures and Pure Substances http://www.elmhurst.edu/~chm/vchembook/171solublesalts.html Animation: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

Class Assignment Work on pages 409-411

The diagram shows five particles of elements and compounds The diagram shows five particles of elements and compounds. Each circle represents an atom of an element. Match the pictures A to E to the following questions. (a) Which particle picture represents a mixture of two compounds? ____ (b) Which particle picture represents a pure compound? ____ (c) Which particle picture represents a mixture of an element and a compound? ____ (d) Which particle picture represents a pure element? ____ (e) Which particle picture represents a mixture of two elements? ____ (f) Which particle picture could represent pure water? ____ (g) Which particle picture could represent something dissolved in water? ____