solubility

SolubilitySolubility

Ch. 22Ch. 22

(With emphasis on section 2)(With emphasis on section 2)

What is a What is a solutionsolution??

► A mixture that has the same composition, A mixture that has the same composition, color, density, and even taste throughout.color, density, and even taste throughout.

► A homogeneous mixtureA homogeneous mixture► Contains two parts:Contains two parts:

1. 1. solute:solute: the substance being dissolved; the substance being dissolved; usually the substance with the lesser amountusually the substance with the lesser amount

2. 2. solvent:solvent:the substance doing the the substance doing the dissolving; usually the substance with the dissolving; usually the substance with the greater amountgreater amount

Name the Name the solutesolute and and solventsolvent in each of the following in each of the following

solutions:solutions: SolutionSolution solutesolute solventsolvent1. Salt water1. Salt water salt watersalt water2. Coke2. Coke

sugar, COsugar, CO22, color water, color water3. Air (pg. 707)3. Air (pg. 707) OO22, H, H22O, COO, CO22 N N

4. Sterling silver (pg. 707)4. Sterling silver (pg. 707) copper, (7.5%) silver (92.5 %)copper, (7.5%) silver (92.5 %)

How can I dissolve a How can I dissolve a solid solid in a in a liquid more quickly?????liquid more quickly?????

1.1. Stir itStir it (agitation) = brings more (agitation) = brings more fresh solvent into contact with more fresh solvent into contact with more solute solute

2.2. Heat the solvent Heat the solvent = speeds up the = speeds up the movement of the particlesmovement of the particles

3.3. Grind the solute into smaller Grind the solute into smaller particlesparticles allows more solute to allows more solute to come into contact with the solventcome into contact with the solvent

To dissolve more GAS into a To dissolve more GAS into a liquid,liquid,

1.1. Increase the pressureIncrease the pressure (Why do (Why do you tap on the top of a can of soda you tap on the top of a can of soda before opening it?)before opening it?)

2.2. Cool the liquid Cool the liquid (Think how “fizzy” a (Think how “fizzy” a HOTHOT coke is compared to a coke is compared to a COLDCOLD coke!) The COcoke!) The CO22 stays in solution stays in solution longer when it is cooler – the longer when it is cooler – the particles move more slowly.particles move more slowly.


►Let’s watch a video on solubility before Let’s watch a video on solubility before we go further.we go further.

G:\videos\G:\videos\Solubility.asfSolubility.asf


► A measure of how much of a solute will A measure of how much of a solute will dissolve in a given volume of solvent at a dissolve in a given volume of solvent at a given temperaturegiven temperature

► As we saw with the NaCl and AgCl, not all As we saw with the NaCl and AgCl, not all substances have the same solubility.substances have the same solubility.

► See Table 2 on pg. 719.See Table 2 on pg. 719.1.1. Which solid has the highest solubility in Which solid has the highest solubility in

100 g of H100 g of H22O?O?2.2. Which gas has the highest solubility in 100 Which gas has the highest solubility in 100

g of Hg of H22O?O?

Concentration of Concentration of SolutionsSolutions

1.1. A A concentrated solution concentrated solution is one in which is one in which a large amount of solute is dissolved in a large amount of solute is dissolved in the solvent. (Anything you have to add the solvent. (Anything you have to add water to before using or drinking)water to before using or drinking)

Ex.: frozen orange juice concentrateEx.: frozen orange juice concentrate

2.2. A A dilute solution dilute solution is one that has a small is one that has a small amount of solute in the solvent amount of solute in the solvent

Ex.: orange juice out of the cartonEx.: orange juice out of the carton

Types of SolutionsTypes of Solutions

1. 1. Saturated :Saturated : contains all the solute it can contains all the solute it can hold at a given temperature (A sponge that hold at a given temperature (A sponge that can not hold any more water – soaked)can not hold any more water – soaked)

2.2. Unsaturated:Unsaturated: can dissolve MORE solute at a can dissolve MORE solute at a given temperature than is in the solution given temperature than is in the solution

Ex.: making koolaidEx.: making koolaid

3. 3. Supersaturated:Supersaturated: contains more solute than contains more solute than a saturated one at the same temperature a saturated one at the same temperature (See pg. 721)(See pg. 721)

Particles in SolutionParticles in Solution

►Why are Why are electrolyteselectrolytes used in sports drinks used in sports drinks and batteries?????and batteries?????

► An An electrolyte electrolyte is a solution that contains is a solution that contains ions that conduct electricity in water.ions that conduct electricity in water.

► Your body works on electrical impulses.Your body works on electrical impulses.► The sports drinks have The sports drinks have sodium ionssodium ions and and

potassium ionspotassium ions that transport signals in that transport signals in the body.the body.

► Batteries contain Batteries contain ammonium ions, sulfate ammonium ions, sulfate ions, ions, andand hydrogen ions hydrogen ions that conduct that conduct electricity in the battery.electricity in the battery.

Effects of Solute ParticlesEffects of Solute Particles

►All solute particles affect the physical All solute particles affect the physical properties of the solvent, such as properties of the solvent, such as freezing point and boiling point.freezing point and boiling point.

►Why do we put “antifreeze” in our cars Why do we put “antifreeze” in our cars in the winter?in the winter?

►Well, why do we put “antifreeze” in our Well, why do we put “antifreeze” in our cars in the cars in the summersummer??

►How can one substance keep your How can one substance keep your radiator from radiator from freezing upfreezing up and from and from overheating?overheating?

Lowering Freezing PointLowering Freezing Point

► By adding antifreeze to your radiator, it By adding antifreeze to your radiator, it lowers the freezing point of the water in lowers the freezing point of the water in the radiator. HOW?the radiator. HOW?

1.1. When a substance freezes, its particles When a substance freezes, its particles arrange themselves in an orderly pattern.arrange themselves in an orderly pattern.

2.2. The antifreeze adds solute particles that The antifreeze adds solute particles that interfere with the formation of this pattern interfere with the formation of this pattern and “get in the way”, making it harder for and “get in the way”, making it harder for the solvent to freeze. the solvent to freeze.

3.3. The temp. has to be much colder before all The temp. has to be much colder before all the water freezes. the water freezes.

See Figure 20 on page 725.See Figure 20 on page 725.

Raising Boiling PointRaising Boiling Point

► By adding antifreeze to your radiator, you By adding antifreeze to your radiator, you can also raise the boiling point and prevent can also raise the boiling point and prevent overheating!overheating!

1.1. Evaporation occurs on the surface of a Evaporation occurs on the surface of a liquid. As the temperature increases, the liquid. As the temperature increases, the movement of the molecules increases and movement of the molecules increases and leave the surface as a gas.leave the surface as a gas.

2.2. By adding antifreeze, the solute particles in By adding antifreeze, the solute particles in the antifreeze “get in the way” and prevent the antifreeze “get in the way” and prevent as many water molecules from getting to as many water molecules from getting to the surface and evaporating. (See Figure the surface and evaporating. (See Figure 21 on pg. 726.)21 on pg. 726.)

3.3. As a result, the temperature has to be As a result, the temperature has to be HIGHER before the water can all evaporate.HIGHER before the water can all evaporate.

So……………………….So……………………….

►Antifreeze particles “get in the way” Antifreeze particles “get in the way” and prevent the water from freezing at and prevent the water from freezing at 0000 C. It must be COLDER for the water C. It must be COLDER for the water to freeze.to freeze.

►Antifreeze particles also “get in the Antifreeze particles also “get in the way” and prevent the water from way” and prevent the water from evaporating at 100evaporating at 10000 C. It must be C. It must be much HOTTER for all the water to much HOTTER for all the water to evaporate.evaporate.

So……….So……….

►Why do we use salt when we make Why do we use salt when we make homemade ice cream?????????????homemade ice cream?????????????

►How Does It Work:How Does It Work:►What does the salt do? Just like we use What does the salt do? Just like we use

salt on icy roads in the winter, salt salt on icy roads in the winter, salt mixed with ice in this case also causes mixed with ice in this case also causes the ice to melt. When salt comes into the ice to melt. When salt comes into contact with ice, the freezing point of contact with ice, the freezing point of the ice is lowered.the ice is lowered.

►The lowering of the freezing point The lowering of the freezing point depends on the amount of salt added. depends on the amount of salt added. The more salt added, the lower the The more salt added, the lower the temperature will be before the salt- temperature will be before the salt- water solution freezes. For example, water solution freezes. For example, water will normally freeze at 32 water will normally freeze at 32 degrees F. A 10% salt solution freezes degrees F. A 10% salt solution freezes at 20 degrees F, and a 20% solution at 20 degrees F, and a 20% solution freezes at 2 degrees F. freezes at 2 degrees F.

►When salt is added to the ice, some of When salt is added to the ice, some of the ice melts because the freezing point the ice melts because the freezing point is lowered. Always remember that heat is lowered. Always remember that heat must be absorbed by the ice for it to must be absorbed by the ice for it to melt. The heat that causes the melting melt. The heat that causes the melting comes from the surroundings (the comes from the surroundings (the warmer cream mixture). By lowering warmer cream mixture). By lowering the temperature at which ice is frozen, the temperature at which ice is frozen, you were able to create an environment you were able to create an environment in which the cream mixture could freeze in which the cream mixture could freeze at a temperature below 32 degrees F at a temperature below 32 degrees F into ice cream. into ice cream.

solubility

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