Unit+3

= Mixtures - Unit 3 = = =

= Physical Properties = = =

According to the **kinetic theory of matter**, all matter is made up of moving particles called molecules. There are four states of matter: solid, liquid, gas, and plasma. The state that matter is in depends on how fast the molecules are moving and how much attraction the molecules hae for one another. In order for matter to change from one state to another, energy must be added or removed. Each substance has its own freezing point, melting point, and boiling point. In other words, different substances change states at different temperatures.

toc || [|Liquid] || [|Gas] || [|Plasma] ||
 * [[image:http://johnson.emcs.net/Physical/images/solid.gif width="109" height="109" align="center" caption="solid"]] || [[image:http://johnson.emcs.net/Physical/images/liquid.gif width="113" height="113" align="center" caption="liquid"]] || [[image:http://johnson.emcs.net/Physical/images/gas.gif width="116" height="116" align="center" caption="gas"]] || [[image:http://johnson.emcs.net/life/images/plasma.gif width="116" height="120" align="center" caption="plasma"]] ||
 * [|Solid]

**Solid**
In a **solid**, the molecules are close together. They do not move around very freely, but they do vibrate. A solid has a definite shape and volume. Solids can be described as crystalline (particles arranged in a regular, definite pattern) or amorphous (particles arranged in no particular order).

**Liquid**
The molecules in a liquid are farther apart than the molecules in a solid. The force of attraction between a liquid's molecules is strong enough to keep the volume constant but not strong enough to give the matter a definite shape. The molecules in a liquid also move faster than the molecules in a solid. **Liquids** have a definite volume but no definite shape.

**Gas**
Compared to the molecules in solids or liquids, the molecules in gases are very far apart. They are also moving very quickly. Because the forces between the molecules are weak, gases have no definite shape or volume. Gases expand to fill and take the shape of whatever container they are in. Gases can be compressed. When they are compressed, their pressure increases.

**Plasma**
When the temperature of a gas is extremely high, some of the gas becomes electrically charged. These charges create new physical properties. The formation of plasma can be simulated in a laboratory. It also occurs naturally inside stars. When clouds of plasma come in contact with the earth's atmosphere, they produce colored lights, or auroras, in the sky.

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5th State of Matter
Several other less common states of matter have also either been described or actually seen. Some of these states include liquid [|crystals], fermionic condensates, superfluids, supersolids and the aptly named strange matter.
 * Bose-Einstein Condensates** represent a fifth state of matter only seen for the first time in 1995. The state is named after [|Satyendra Nath Bose] and [|Albert Einstein] who predicted its existence in the 1920’s. B-E condensates are gaseous superfluids cooled to temperatures very near [|absolute zero]. In this weird state, all the [|atoms] of the condensate attain the same quantum-mechanical state and can flow past one another without friction. Even more strangely, B-E condensates can actually “trap” [|light], releasing it when the state breaks down.

Phase Changes
One way to separate two substances from one another in a physical mixture is to take advantage of differences in their boiling points. Distillation is the technique used for this kind of separation. However sometimes one of the substances to be separated will chemically decompose before it reaches its boiling point. One way to remedy this problem is to reduce the pressure within the distilling flask sufficiently to lower the boiling point of the substance below it decomposition point. This is called reduced pressure distillation and is a common technique used among Organic Chemists.

=Mixtures= **Mixtures** are physical combinations of two or more pure substances (elements or compounds). As a physical combination one should be able to separate these substances from the mixture by physical methods so that no chemical change can take place during the separation. Substances can be separated from the mixture by taking advantage of any differences the substances have in physical properties. For example, most pure substances have different boiling points (temperature at which a substance will boil). If we can heat a mixture so that the lowest boiling substance will boil off before any other substance begins to boil, we will effectively be able to separate that substance from the mixture. One such laboratory resolution method is known as distillation. Other separation techniques include chromatography, settling out, filtering, evaporation, and centrifuging.
 * **Properties of Elements, Compounds, and Mixtures** ||
 * **Elements** || **Compounds** || **Mixtures** ||
 * made up of only one kind of atom || made up of more than one kind of atom || made up of more than one kind of molecule ||
 * can not be broken down by chemical means || can not be broken down by physical means || can be broken down by physical means ||
 * has same properties as atoms making it up || has different properties from elements making it up || has same properties as substances making it up ||
 * has same properties throughout || has same properties throughout || has different properties throughout ||

Mixtures can be classified according to how well they are mixed together. There are two kinds of mixtures: **heterogeneous** and **homogeneous.**

Heterogeneous Mixtures
The matter in most mixtures is heterogeneous. The substances in a heterogeneous mixture are not chemically combined and the individual substances are still visible. Each substance keeps its own identity and most of its own properties. No new substances are formed because the chemical composition of the substances have not changed. A substance in a mixture can be present in any amount and can be separated by physical means. The substances that make up a mixture determine the mixture's properties.

Homogeneous Mixtures
In a homogeneous mixture, the parts look the same throughout because their components are uniformly mixed together. Homogeneous mixtures are uniform in their distribution. If we took a sampling anywhere in the mixture, and then analyzed it as to its composition for each component we would find that the distribution was the same throughout the mixture. All solutions are said to be homogeneous mixtures.

=Separation Techniques= Most materials in our world are mixtures. Very few materials are pure substances. The art of separating mixtures is important because it enables us to isolate pure substances. Mixtures are either homogeneous or heterogeneous. Homogeneous mixtures are uniform in composition. Heterogeneous mixtures are not. Salt water is a mixture of water and NaCl and is homogeneous if thoroughly mixed, with all the salt dissolved. Oil in water is a heterogeneous mixture. Both types of mixtures can be separated into their component parts by physical means. A salt water mixture can be separated by distilling or evaporating the water and collecting the salt residue. An oil and water mixture will separate into an oil layer and a water layer because the materials are not attracted to one another and gravity "pulls" the denser water beneath the less dense oil. Settling, magnetic attraction, distillation, decantation, solubility, evaporation, filtration, chromatography, and manual methods are all means of separating the components of a mixture. Choice of method depends on the type of mixture and the characteristics of its components.

A heterogeneous mixture of solid and liquid or solid and gas is usually fairly easy to separate because of the 2 different physical phases. The solid may settle out, allowing you to pour off the liquid. This is called **//decantation//**. Or, maybe the liquid can be evaporated, leaving the solid behind. Or the mixture can be poured through a filter, catching the solid on the filter and allowing the liquid or gas to pass through. We use filtration frequently--in our coffee makers, automobile fuel lines, automobile air cleaners to name only a few examples.

A mixture of two or more solids is usually separated by utilizing the different chemical or physical properties of the substances. For example, a heterogeneous mixture of red M&M's and yellow jellybeans can be separated using the different colors or the different shapes of the solids. The parts of the mixture are large enough to be separated manually. A mixture of black peppercorns and white table salt might be separated this way as well. But what could be done with a mixture of sand and sugar? True, you could get a magnifying glass and tweezers and try picking out the grains of sand, but is there an easier way? Is there some property that sugar has that sand does not (or vice versa)? Could this be used to separate sand and sugar? If you said that sugar dissolves in water and sand does not, you are on the right track.

Homogeneous mixtures of a solvent and one or more solutes (dissolved substances) are often separated by chromatography. Chromatography works to separate a mixture because the components of a mixture distribute themselves differently. Food colorings are one example, a homogeneous mixture of a solvent and a single dye or combination of selected dyes that produce the desired color.

=Solutions= A **solution** is a homogeneous mixture in which one substance is dissolved in another substance. In a solution, two or more substances are uniformly mixed. The solution formed is the same in all parts. In a sugar-water solution, molecules of sugar are evenly spread throughout the molecules of water. Solutions consist of two parts: the solute and the solvent. The **solute** is the substance being dissolved. The **solvent** is the substance in which a solute is dissolved. The the sugar-water solution, sugar is the solute and the water is the solvent. The substance present in the largest amount is usually called the solvent. The most common solutions are those in which the solvent is a liquid. The solute can be a solid, gas or liquid. A solution with water as the solvent is called an **aqueous solution**. Water is considered to be a **universal solvent**. Another common solvent is alcohol. A solution with alcohol as the solvent is called a **tincture**. However, other types of solutions can be formed.
 * **Types of Solutions** ||
 * **Solvent** || **Solute** || **Example** ||
 * liquid || liquid || antifreeze ||
 * ^  || solid || sugar water ||
 * ^  || gas || soft drink ||
 * gas || liquid || humidity ||
 * ^  || solid || mothballs ||
 * ^  || gas || air ||
 * solid || liquid || dental fillings ||
 * ^  || solid || steel ||
 * ^  || gas || gas stove lighter ||

The Solution Process
When sugar is added to water, a solution forms. The dissolving action takes place on the surface of the crystal. Water molecules surround the surface molecules of sugar. The sugar molecules are held together only by weak bonding forces. The sugar molecules are attracted more to the water molecules than to each other. surround by water molecules, surface sugar molecules are carried away from the crystal surface. the process of diffusion causes the sugar molecules to distribute evenly within the water molecules. As the outer layer of molecules dissolves, the next layer is exposed to the water molecules. This process continues until all the sugar molecules are separated from each other and mixed evenly throughout the solution. Check out this animation to see how salt dissolves in water.

Rate of Solution
1. When a solution is stirred, particles of the solute move away form the crystal surface at a higher rate. This exposes more particles to the solvent sooner. Thus the solute dissolves at a faster rate. 2. Solution action occurs only at the surface of the solid solute. So if the surface area of the solute is increased, the rate of solution is increased. More solute molecules are in contact with the solvent when the solid solute is ground into a find powder. 3. If heat is applied to a solution, the molecules move faster and farther apart. As a result, the dissolving action is speeded up. Water is the most common substance on the earth. Water plays an important role in dissolving a great variety of substances. Because thousands of substances are soluble in water, water is sometimes called the universal solvent. However, you should also remember, that there are certain substances that will not dissolve in water. These substances are described as insoluble.

Solubility Factors
The solubility of a solute is a measure of how much of that solute can be dissolved a given amount of solvent under certain conditions. Two main factors that affect the solubility of a solute are temperature and pressure. Generally, an increase in the temperature of a solution increases the solubility of a solid in a liquid. The solubility of most solids is increased by raising the temperature of the solution. Raising the temperature of a gas-in-liquid solution decreases the solubility of the gaseous solute. Thus, the solubility of a gas is decreases as the temperature of the solution increases. For solid and liquid solutes, increases and decreases in pressure have practically no effect on solubility. For gases dissolved in liquids, an increase in pressure increases solubility and a decrease in pressure decreases solubility.

=Concentration= If you add too much water when you make a can of frozen orange juice, it tastes weak. In other words, there are not enough solute particles for the amount of solvent to taste pleasing. Whenever you express a relationship between the amount of solute and the amount of solvent, you are identifying the **concentration**. Concentration is the amount of solute per given volume of solvent. You can also classify solutions as saturated, unsaturated, or supersaturated.

A **saturated solution** is a solution that contains all the solute it can possible hold at a given temperature. If additional solute is added to a saturated solution, it will settle undissolved to the bottom of the solution. Saturation is dependent on temperature. A solution that contains less solute than this amount is called **unsaturated**. An unsaturated solution can range from dilute to concentrated. A dilute solution contains very little solute. A concentrated solution contains a large amount of solute. Because these terms are not precise, you can refer to a wide range of actual concentrations.

In some cases you can make a **supersaturated** solution. This is a solution in which the solvent can hold more solute than normal. You make a supersaturated solution at a high temperature and then cool it very slowly. At room temperature, it will contain more solute than could normally dissolve at that temperature. This type of solution is very unstable. If the solution is not disturbed, all the solute will stay dissolved. If the smallest amount of solute is added to the supersaturated solution, the excess solute comes out of the solution and settles to the bottom. Only enough solute to make the solution saturated remains dissolved.

It is often important to be precise about the concentration of solution. Concentration describes the relative amounts of solute and solvent present in a solution. The concentrations of solutions are often expressed as a percent concentration. This provides information about the relative amount of solute or solvent present, assuming a total of 100 parts of solution. For example, a bottle of rubbing alcohol contains 70% isopropyl alcohol by volume. This means that there are 70 parts of isopropyl alcohol in the total 100 parts of the rubbing alcohol solution. When the solute is a liquid, the percent concentration is often determined by finding the percent by volume. To find the percent by volume, you divide the volume of the solute by the total volume of the solution and multiply the result by 100.

Percent by volume = __volume of solute__ x 100 total volume of solution

For problems 1 through 5, use the "Mixing Orange Juice" applet to check your answers to the problems in the "Orange Juice Mixture" problem. (You need to decide whether one mixture will taste more "orangey" than the other or whether they will taste the same.)  ||   || In problems 6 through 8, use the applet to compare the two mixtures. Come up with a way to reliably determine which mixture is more "orangey" than the other or whether they are the same amount of "orangeyness." || ||
 * 1. ||~ Mixture 1 ||~ Mixture 2 ||
 * [[image:http://www.pbs.org/teacherline/resources/activities/images/dot_transparent.gif width="9" height="8"]] || 
 * 2. ||~ Mixture 1 ||~ Mixture 2 ||
 * ||  [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/3-2.gif width="150" height="40" align="center" caption="3 Orange 2 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/4-3.gif width="180" height="40" align="center" caption="4 Orange 3 Water"]] ||
 * 3. ||~ Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/3-2.gif width="150" height="40" align="center" caption="3 Orange 2 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/2-1.gif width="90" height="40" align="center" caption="2 Orange 1 Water"]] ||
 * <span style="font-family: Arial,Helvetica,sans-serif;">4. ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/3-2.gif width="150" height="40" align="center" caption="3 Orange 2 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/6-4.gif width="180" height="40" caption="6 Orange 4 Water"]] ||
 * <span style="font-family: Arial,Helvetica,sans-serif;">5. ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/1-1-1-2.gif width="150" height="40" align="center" caption="1 Orange 1 Water 1 Orange 2 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/2-1-1-3.gif width="180" height="40" caption="2 Orange 1 Water 1 Orange 3 Water"]] ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/3-2.gif width="150" height="40" align="center" caption="3 Orange 2 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/6-4.gif width="180" height="40" caption="6 Orange 4 Water"]] ||
 * <span style="font-family: Arial,Helvetica,sans-serif;">5. ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/1-1-1-2.gif width="150" height="40" align="center" caption="1 Orange 1 Water 1 Orange 2 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/2-1-1-3.gif width="180" height="40" caption="2 Orange 1 Water 1 Orange 3 Water"]] ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/1-1-1-2.gif width="150" height="40" align="center" caption="1 Orange 1 Water 1 Orange 2 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/orangejuice/2-1-1-3.gif width="180" height="40" caption="2 Orange 1 Water 1 Orange 3 Water"]] ||
 * <span style="font-family: Arial,Helvetica,sans-serif;">6. ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * <span style="font-family: Arial,Helvetica,sans-serif;">[[image:http://www.pbs.org/teacherline/resources/activities/images/dot_transparent.gif width="9" height="8"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/comparemix/1-1-1-2-1-1.gif width="180" height="40" caption="1 Orange 1 Water 1 Orange 2 Water 1 Orange 1 Water"]]
 * <span style="font-family: Arial,Helvetica,sans-serif;">7. ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/comparemix/1-2-1-1-1-1.gif width="180" height="40" caption="1 Water 2 Orange 1 Water 1 Orange 1 Water 1 Orange"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/comparemix/1-2-2-1-1-2.gif width="180" height="40" caption="1 Water 2 Orange 2 Water 1 Orange 1 Water 2 Orange"]] ||
 * <span style="font-family: Arial,Helvetica,sans-serif;">8. ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/comparemix/1-1-1-1-1-1-3.gif width="180" height="40" caption="1 Water 1 Orange 1 Water 1 Orange 1 Water 1 Orange 3 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/comparemix/1-1-3-1.gif width="151" height="40" align="center" caption="1 Water 1 Orange 3 Water 1 Orange"]] ||
 * <span style="font-family: Arial,Helvetica,sans-serif;">8. ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 1 ||~ <span style="font-family: Arial,Helvetica,sans-serif;">Mixture 2 ||
 * || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/comparemix/1-1-1-1-1-1-3.gif width="180" height="40" caption="1 Water 1 Orange 1 Water 1 Orange 1 Water 1 Orange 3 Water"]] || [[image:http://www.pbs.org/teacherline/resources/activities/mixing_orange_juice/comparemix/1-1-3-1.gif width="151" height="40" align="center" caption="1 Water 1 Orange 3 Water 1 Orange"]] ||

=Suspensions and Colloids= A **suspension** is a mixture in which particles of a material are dispersed throughout a liquid or gas but are large enough that they settle out. The particles are insoluble so they will not dissolve. Suspensions are often described as heterogeneous mixtures because the different components are easily seen. Examples include snow globe, muddy water, and Italian salad dressing. The particles in a suspension are fairly large and they scatter or block light. This often makes a suspension difficult to see through. But the particles are too heavy to remain mixed without being stirred or shaken. If a suspension is allowed to sit undisturbed, the particles will settle out. Passing it through a filter can separate a suspension. The liquid or gas passes through, but the solid particles are large enough to be trapped by the filter.

Some mixtures have properties of both solutions and suspensions. These mixtures are known as colloids. A **colloid** is a mixture in which the particles are dispersed throughout but are not heavy enough to settle out. The particles in a colloid are relatively small and are fairly well mixed. But the particles are not dissolved. Although the particles are too small to be seen by the unaided eye, they are large enough to reflect a beam of light off their surfaces. When you pass a beam of light through a colloid, the beam becomes visible, just as it does in a suspension. A beam of light is not visible when it passes through a solution.

Solids, liquids, and gases can be used to make colloids. Milk, mayonnaise, gelatin, whipped cream, and stick deodorant are colloids. A colloid can not be separated by filtration. The particles are small enough to pass through a filter. A colloid will not settle out as a suspension. There are many types of colloids: **1. Sols** This is a colloid that is made up of a solid dispersed in either a solid or a liquid. Many paints and inks are liquid sols. They contain tiny particles of pigment dispersed in a liquid. Putty, toothpaste and potter's clay are sols. **2. Gels** A gel is a jelly like colloid in which long particles form a branching structure that traps a liquid inside. A liquid in a solid. Gels behave like flexible solids. Examples include jelly, jam, cheese, Jell-O and styling gel. **3. Aerosols** Smoke, clouds, fog and mist are natural colloids called aerosols. They are made up of solid or liquid particles dispersed in the air. Some pray cans contain artificial aerosols. The fine mist they produce consists of liquid or solid particles dispersed in a gas. **4. Foams** A gas may be dispersed in a liquid to form a foam (e.g., shaving lather or beaten egg white) or in a solid to form a solid foam (e.g., Styrofoam or marshmallow). Foam is colloid of gas bubbles dispersed in liquid. Whipped cream, marshmallows, and shaving cream are common examples of foam. **5. Emulsions** A colloid made up of tiny droplets of a liquid in another liquid is an emulsion. Because the particles in an emulsion cling to each other, they do not settle out. Milk, butter, and margarine are all emulsions of oil in water. Most creams and ointments used in cosmetics and medicine are also emulsions.