Chapter 14Chapter 14Section 14.1Section 14.1

Types of MixturesTypes of Mixtures

Types of MixturesTypes of Mixtures

A A mixturemixture is a combination of two or more pure is a combination of two or more pure substances that are substances that are notnot chemically combined chemically combined

No Chemical Changes in a Mixture No Chemical Changes in a Mixture No No chemical changes happen when a mixture is chemical changes happen when a mixture is made. So, each substance has the same made. So, each substance has the same chemical makeup it had before the mixture was chemical makeup it had before the mixture was formed. Making a mixture is a formed. Making a mixture is a physical change. physical change.

Types of Mixtures

TYPES OF MIXTURESTYPES OF MIXTURES A- Heterogeneous mixture: A- Heterogeneous mixture: mixture in mixture in

which individual substances remain which individual substances remain distinct.distinct. The different components can be The different components can be seen as individual substances. We can seen as individual substances. We can almost separate the components with our almost separate the components with our eyes. The particles are visible (bigger eyes. The particles are visible (bigger particles)particles)

Heterogeneous mixturesHeterogeneous mixtures

Heterogeneous mixtures are those where Heterogeneous mixtures are those where the substances are not distributed evenlythe substances are not distributed evenly

There are two types of Heterogeneous There are two types of Heterogeneous mixtures:mixtures:

1- 1- SUSPENSIONS: SUSPENSIONS: is a mixture in which particles is a mixture in which particles of a material are dispersed throughout a liquid of a material are dispersed throughout a liquid or a gas but are large enough that they settle or a gas but are large enough that they settle out if left undisturbed . out if left undisturbed . A suspension can be A suspension can be separated by passing it through a filterseparated by passing it through a filter. . So So suspension will separate into 2 distinct layers if suspension will separate into 2 distinct layers if left undisturbed for awhile; water on the top left undisturbed for awhile; water on the top and solidlike on the bottom. When stirred, the and solidlike on the bottom. When stirred, the solidlike substance quickly begins flowing like a solidlike substance quickly begins flowing like a liquid, substances behave like this is calledliquid, substances behave like this is called thixotropic thixotropic

There are two types of Heterogeneous There are two types of Heterogeneous mixtures:mixtures:

2- COLLOIDS: 2- COLLOIDS: is a mixture in which the is a mixture in which the particles are spread throughout but are particles are spread throughout but are not large enough to settle out. Particles not large enough to settle out. Particles diameter is between 1 nm to 1000 nm. diameter is between 1 nm to 1000 nm. Milk is a colloid; Milk is a colloid; Its components can not be Its components can not be separated by settling or filtrationseparated by settling or filtration

The most abundant substance in the The most abundant substance in the mixture is the dispersion mediummixture is the dispersion medium

Colloids are categorized according to the Colloids are categorized according to the phases of their dispersed particles and phases of their dispersed particles and dispersing mediums.dispersing mediums.

Types of colloids Types of colloids Category Example Dispersed Particles Dispersing Medium

Solid sol colored gems solid solid

Sol blood, gelatin solid liquid

Solid emulsion butter, cheese liquid solid

Emulsion milk, mayonnaise liquid liquid

Solid foam marshmallow, soaps that float gas solid

Foam whipped cream, beaten egg white

gas liquid

Solid aerosol smoke, dust in air solid gas

Liquid aerosol spray deodorant, fog, clouds liquid gas

Explain why?Explain why?

Explain why The dispersed particles in a Explain why The dispersed particles in a colloid are prevented from settling out?colloid are prevented from settling out?

because The dispersing medium particles because The dispersing medium particles form charged layers around the colloid form charged layers around the colloid particles. These charged layers repel each particles. These charged layers repel each other and keep the particles from settling other and keep the particles from settling out.out.

How?How? How can you settle colloid particles out of How can you settle colloid particles out of

the mixture?the mixture?

1- If you interfere with the electrostatic 1- If you interfere with the electrostatic layering, colloid particles will settle out of layering, colloid particles will settle out of the mixture. For example, if you stir an the mixture. For example, if you stir an electrolyte into a colloid, the dispersed electrolyte into a colloid, the dispersed particles clump together, destroying the particles clump together, destroying the colloid.colloid.

2- Heating also destroys a colloid because it 2- Heating also destroys a colloid because it gives colliding particles enough kinetic gives colliding particles enough kinetic energy to overcome the electrostatic forces energy to overcome the electrostatic forces and settle out.and settle out.

Brownian motionBrownian motion

Brownian motion Brownian motion is the erratic movement of is the erratic movement of colloid particles.colloid particles.

Explain how Brownian motion results? Explain how Brownian motion results?

It results from collisions of particles of the It results from collisions of particles of the dispersion medium with the dispersed particles. dispersion medium with the dispersed particles. These collisions help to prevent the colloid These collisions help to prevent the colloid particles from settling out of the mixture. particles from settling out of the mixture.

Colloids exhibit the Colloids exhibit the Tyndall effectTyndall effect. Which . Which happened when dispersed colloid particles happened when dispersed colloid particles scatter lightscatter light

Tyndall effectTyndall effect

TYPES OF MIXTURESTYPES OF MIXTURES 2- 2- HOMOGENEOUS MIXTURES: HOMOGENEOUS MIXTURES: Composed of Composed of

two or more substances and have variable two or more substances and have variable composition composition BUTBUT The particles are distributed The particles are distributed evenly throughout each other evenly throughout each other SO SO

the composition is uniform the composition is uniform the solution appears to be one substancethe solution appears to be one substance When you look at a solution, it is not possible to When you look at a solution, it is not possible to

distinguish the solute from the solventdistinguish the solute from the solvent..

Solutions:Solutions: are groups of molecules that are are groups of molecules that are mixe up in a completely even distribution mixe up in a completely even distribution

• • A solution consists of aA solution consists of a

1- 1- solutesolute: dissolved in a solvent.: dissolved in a solvent.

2- 2- SolventSolvent: substance that dissolves another: substance that dissolves another• continuous phase -salt dissolved in water continuous phase -salt dissolved in water

appears to be a liquidappears to be a liquid

Types of solutions:Types of solutions:A solution might exist as a gas, a liquid, or a A solution might exist as a gas, a liquid, or a solid, depending on the state of its solventsolid, depending on the state of its solvent

Forming solutionsForming solutions

A substance that dissolves in a solvent is said A substance that dissolves in a solvent is said to be to be solublesoluble in that solvent. For example, in that solvent. For example, sugar is soluble in watersugar is soluble in water

Two Two liquidsliquids that are soluble in each other in any that are soluble in each other in any proportion, such as those that form the proportion, such as those that form the antifreeze are said to be antifreeze are said to be misciblemiscible

A substance that does not dissolve in a solvent A substance that does not dissolve in a solvent is said to be is said to be insolubleinsoluble in that solvent. Sand is in that solvent. Sand is insoluble in water.insoluble in water.

Two Two liquidsliquids that can be mixed together but that can be mixed together but separate shortly after are said to be separate shortly after are said to be immiscible.immiscible.

QuestionsQuestions

Q: Distinguish between suspensions and colloids. Q: Distinguish between suspensions and colloids. Suspension particles are larger than colloidal Suspension particles are larger than colloidal

particles. Suspension particles settle out of the particles. Suspension particles settle out of the mixture, whereas colloidal particles do not. mixture, whereas colloidal particles do not.

Q: Identify the various types of solutions. Describe Q: Identify the various types of solutions. Describe the characteristics of each type of solution.the characteristics of each type of solution.

All solutions are homogeneous mixtures All solutions are homogeneous mixtures containing two or more substances. Solutions containing two or more substances. Solutions might be liquid, solid, or gas. Solution types are might be liquid, solid, or gas. Solution types are identified in Table 14.2.identified in Table 14.2.

QuestionsQuestions Q: Explain Use the Tyndall effect to explain Q: Explain Use the Tyndall effect to explain

why it is more difficult to drive through fog why it is more difficult to drive through fog using high beams than using low beams.using high beams than using low beams.

High beams are aimed farther down the road High beams are aimed farther down the road than low beams. Because the fog scatters light, than low beams. Because the fog scatters light, there is less light from the high beams to there is less light from the high beams to illuminate the road than from the low beams. illuminate the road than from the low beams. Also, because the high beams are aimed more Also, because the high beams are aimed more directly into the fog, more of their light is directly into the fog, more of their light is reflected back toward the driver, making it reflected back toward the driver, making it more difficult to see.more difficult to see.

QuestionsQuestions Q: Explain Why do dispersed colloid particles Q: Explain Why do dispersed colloid particles

stay dispersed? stay dispersed? The particles do not settle out because they The particles do not settle out because they

have polar or charged layers surrounding them. have polar or charged layers surrounding them. These layers repel each other and prevent the These layers repel each other and prevent the particles from settling or separating.particles from settling or separating.

Q: Summarize What causes Brownian motion?Q: Summarize What causes Brownian motion? Collisions of particles of the dispersion medium Collisions of particles of the dispersion medium

with the dispersed particles results in Brownian with the dispersed particles results in Brownian motion. motion.

QuestionsQuestionsQ: Make a comparison between solution, colloid and suspension

End of section 14.1