Chapter 8: Solutions

Can it be separated by physical means? Matter Flowchart MATTER yes no Can it be separated by physical means? MIXTURE PURE SUBSTANCE Is the composition uniform? no yes Can it be decomposed by chemical means? no yes Homogeneous Mixture Heterogeneous Mixture Compound Element

A mixture is composed of two or more substances physically combined. Mixtures A mixture is composed of two or more substances physically combined. - not chemically combined.

Mixtures A heterogeneous mixture is made up of different and easily distinguishable material. Ex. are: concrete, pizza, trail mix, granite, muddy water, fruit juice, fresh-squeezed lemonade

Heterogeneous Mixtures Particles in a *suspension (a type of heterogeneous mixture) are large and settle out. Ex. are:   river water, orange juice

Suspensions Examples of Suspensions Mud or muddy water, is where soil, clay, or silt particles are suspended in water. Flour suspended in water, as pictured to the right. Paint Chalk powder suspended in water. Dust particles suspended in air. Algae in water Milk of Magnesia

Heterogeneous Mixtures Particles in a suspension may be filtered out. Through *filtration, you can use a filter made up of porous paper to catch the suspended pulp in orange juice.

Heterogeneous Mixtures One way to separate two *immiscible liquids - liquids that do not mix, is through the process of pouring a less dense liquid off a denser liquid is called *decanting. Ex. are: salad dressing

Density may be thought of as how heavy an object is for its size. The density of the liquid, water, is 1.00 g/cm3.

Heterogeneous Mixtures Another type of heterogeneous mixture is a *colloid - a mixture consisting of tiny particles that are in between the size of particles in solutions and suspensions. Ex. Latex Paint, milk, fog, smoke. Light can be scattered through a colloid known as the *Tyndall effect. Ex. Headlights in fog.

non transparent, non uniform, large particles, cloudy (milky) Colloids Colloids non transparent, non uniform, large particles, cloudy (milky)

*emulsion - any mixture of two or more immiscible liquids in which one liquid is dispersed in the other.

A homogeneous mixture contains materials that are mixed evenly. Mixtures A homogeneous mixture contains materials that are mixed evenly. very small particles particles never settle EX: cola, vinegar, saline solution

Homogeneous Mixtures Ex. Saltwater is NaCl and H2O. These do not chemically combine, so the two substances can be separated by *evaporating the water. Only salt is left.

Homogeneous Mixtures Another name for homogeneous mixture is a *solution. When you add salt to water and stir, the solid seems to disappear. The salt has dissolved in water to form a solution.

Homogeneous Mixtures In this solution, the salt (sodium chloride) is the substances that dissolves, the *solute.

Homogeneous Mixtures In this solution, the salt (sodium chloride) is the substances that dissolves, the *solute. Water is the substance in which the solute dissolves, so water is the *solvent.

Solutions Well-mixed (uniform) – single phase homogeneous cannot be separated by filter do not separate on standing

States of matter in solution Example of solutions gas in gas air ( N2, O2 , Ar, CO2 , other gases) gas in liquid soda pop (CO2 in water) liquid in liquid gasoline (a mixture of hydrocarbon compounds) solid in liquid Filtrated sea water ( NaCl and other salts in water) gas in solid H2 in platinum or palladium liquid in solid dental amalgams (mercury in silver) solid in solid alloys ( brass, (Cu/Zn), sol-der (Sn/Pb), Steel (Fe/C ))

Miscible liquids mix to form solutions *Miscible liquids mix to form solutions. Two or more liquids that form a single layer when mixed are miscible. This is a little harder to separate. One way to separate the liquids is by *distillation. Distillation separates miscible liquids that have different boiling points.

Homogeneous Mixtures Ex. A mixture of methanol and water can be separated by distillation because methanol boils at 64.5 degrees Celsius, and water boils at 100 degrees Celsius. When the mixture is heated, the methanol boils away first, leaving the water.

Distillation

[After passing through a muddy pond, the water in a stream contains dirt particles. Which of the following describes the stream?] [solution] [suspension] [pure substance] [colloid]

[Which of the following will show the Tyndall Effect] [water] [sugar water] [oxygen gas] [fog]

[Which of the following is a colloid] [milk] [NaCl in water] [sand and water] [raisin bread]

Section 2: Remember that particle size/surface area can change the reaction rate. How? Smaller pieces (granulated sugar) have more surface area that is in contact with the solvent (water). There are more collisions between the solute particles and solvent.

Ex. on page 271

Water is called the Universal Solvent because many substances can dissolve in water.

Water is. polar because of the unevenly shared electrons Water is *polar because of the unevenly shared electrons. Water dissolves many ionic compounds because the negative side of the water molecules attracts the positive ions and the positive side of the water molecules attract the negative ions.

*Agitation can change the reaction rate. How? Sugar molecules are always moving (*kinetic theory of matter). They will *diffuse, or spread out in water.

Stirring or shaking the solution moves the dissolved sugar away from the sugar crystals. So more interaction occurs between the water and sugar crystals.

Section 3: Some substances are *insoluble, or do not dissolve. Ex. Olive oil and water. Some substances are *soluble, or do dissolve. Ex. Sugar in water.

Section 3: There is often a limit of how much of a substance will dissolve. Try putting a large amount of salt in a glass of water. No matter how much stirring, shaking, or heating the solution, some of the salt will not dissolve. The maximum amount of salt that can dissolve in 100g of water at room temperature is 36g, or about two tablespoons.

Section 3: *Solubility – the ability of one substance to dissolve in another at a given temperature and pressure.

Section 3: *Concentration – the quantity of solute that is dissolved in a given volume of solution. A concentrated solution has a large amount of solute. A dilute solution has only a small amount of solute.

Section 3: When you have added the maximum amount of solute that will dissolve in a solution, you have made a *saturated solution. No more solute will dissolve. So if you add more solute, it just settles to the bottom.

Section 3: An *unsaturated solution contains less than the maximum amount of solute that will dissolve in the solvent. If you add more, it will keep dissolving until it is saturated.

Section 3: Remember that temperature can change the reaction rate. How? The higher the temperature, the faster the particles dissolve.

Section 3: If you heat the solution, more solute will dissolve. This is known as *supersaturated solution – a solution that holds more dissolved solute than is required to reach equilibrium.