Chapter 14 Section 14.1 Types of Mixtures

Types of Mixtures A mixture is a combination of two or more pure substances that are not chemically combined

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

TYPES OF MIXTURES A- Heterogeneous mixture: mixture in which individual substances remain distinct. The different components can be seen as individual substances. We can almost separate the components with our eyes. The particles are visible (bigger particles)

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

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

There are two types of Heterogeneous mixtures: 2- COLLOIDS: is a mixture in which the particles are spread throughout but are not large enough to settle out. Particles diameter is between 1 nm to 1000 nm. Milk is a colloid; Its components can not be separated by settling or filtration The most abundant substance in the mixture is the dispersion medium Colloids are categorized according to the phases of their dispersed particles and dispersing mediums.

Types of colloids Category Example Dispersed Particles Dispersing Medium Solid sol colored gems solid Sol blood, gelatin liquid Solid emulsion butter, cheese Emulsion milk, mayonnaise Solid foam marshmallow, soaps that float gas Foam whipped cream, beaten egg white Solid aerosol smoke, dust in air Liquid aerosol spray deodorant, fog, clouds

Explain why? Explain why The dispersed particles in a colloid are prevented from settling out? because The dispersing medium particles form charged layers around the colloid particles. These charged layers repel each other and keep the particles from settling out.

How? How can you settle colloid particles out of the mixture? 1- If you interfere with the electrostatic layering, colloid particles will settle out of the mixture. For example, if you stir an electrolyte into a colloid, the dispersed particles clump together, destroying the colloid. 2- Heating also destroys a colloid because it gives colliding particles enough kinetic energy to overcome the electrostatic forces and settle out.

Brownian motion Brownian motion is the erratic movement of colloid particles. Explain how Brownian motion results? It results from collisions of particles of the dispersion medium with the dispersed particles. These collisions help to prevent the colloid particles from settling out of the mixture. Colloids exhibit the Tyndall effect. Which happened when dispersed colloid particles scatter light

Tyndall effect

TYPES OF MIXTURES 2- HOMOGENEOUS MIXTURES: Composed of two or more substances and have variable composition BUT The particles are distributed evenly throughout each other SO the composition is uniform the solution appears to be one substance When you look at a solution, it is not possible to distinguish the solute from the solvent.

Solutions: are groups of molecules that are mixe up in a completely even distribution • A solution consists of a 1- solute: dissolved in a solvent. 2- Solvent: substance that dissolves another continuous phase -salt dissolved in water appears to be a liquid

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

Forming solutions A substance that dissolves in a solvent is said to be soluble in that solvent. For example, sugar is soluble in water Two liquids that are soluble in each other in any proportion, such as those that form the antifreeze are said to be miscible A substance that does not dissolve in a solvent is said to be insoluble in that solvent. Sand is insoluble in water. Two liquids that can be mixed together but separate shortly after are said to be immiscible.

Questions Q: Distinguish between suspensions and colloids. Suspension particles are larger than colloidal particles. Suspension particles settle out of the mixture, whereas colloidal particles do not. Q: Identify the various types of solutions. Describe the characteristics of each type of solution. All solutions are homogeneous mixtures containing two or more substances. Solutions might be liquid, solid, or gas. Solution types are identified in Table 14.2.

Questions Q: Explain Use the Tyndall effect to explain why it is more difficult to drive through fog using high beams than using low beams. High beams are aimed farther down the road than low beams. Because the fog scatters light, there is less light from the high beams to illuminate the road than from the low beams. Also, because the high beams are aimed more directly into the fog, more of their light is reflected back toward the driver, making it more difficult to see.

Questions Q: Explain Why do dispersed colloid particles stay dispersed? The particles do not settle out because they have polar or charged layers surrounding them. These layers repel each other and prevent the particles from settling or separating. Q: Summarize What causes Brownian motion? Collisions of particles of the dispersion medium with the dispersed particles results in Brownian motion.

Questions Q: Make a comparison between solution, colloid and suspension

End of section 14.1