Solubility Ch. 22 (With emphasis on section 2)

What is a solution? ► A mixture that has the same composition, color, density, and even taste throughout. ► A homogeneous mixture ► Contains two parts: 1. solute: the substance being dissolved; usually the substance with the lesser amount 2. solvent:the substance doing the dissolving; usually the substance with the greater amount

Name the solute and solvent in each of the following solutions: Solution solute solvent Solution solute solvent 1. Salt water salt water salt water 2. Coke sugar, CO 2, color water sugar, CO 2, color water 3. Air (pg. 707) O 2, H 2 O, CO 2 N O 2, H 2 O, CO 2 N 4. Sterling silver (pg. 707) copper, (7.5%) silver (92.5 %) copper, (7.5%) silver (92.5 %)

How can I dissolve a solid in a liquid more quickly????? 1. Stir it (agitation) = brings more fresh solvent into contact with more solute 2. Heat the solvent = speeds up the movement of the particles 3. Grind the solute into smaller particles allows more solute to come into contact with the solvent

To dissolve more GAS into a liquid, 1. Increase the pressure (Why do you tap on the top of a can of soda before opening it?) 2. Cool the liquid (Think how “fizzy” a HOT coke is compared to a COLD coke!) The CO 2 stays in solution longer when it is cooler – the particles move more slowly.

Solubility ► Let’s watch a video on solubility before we go further. G:\videos\Solubility.asf

Solubility ► A measure of how much of a solute will dissolve in a given volume of solvent at a given temperature ► As we saw with the NaCl and AgCl, not all substances have the same solubility. ► See Table 2 on pg Which solid has the highest solubility in 100 g of H 2 O? 2. Which gas has the highest solubility in 100 g of H 2 O?

Concentration of Solutions 1. A concentrated solution is one in which a large amount of solute is dissolved in the solvent. (Anything you have to add water to before using or drinking) Ex.: frozen orange juice concentrate Ex.: frozen orange juice concentrate 2. A dilute solution is one that has a small amount of solute in the solvent Ex.: orange juice out of the carton Ex.: orange juice out of the carton

Types of Solutions 1. Saturated : contains all the solute it can hold at a given temperature (A sponge that can not hold any more water – soaked) 2. Unsaturated: can dissolve MORE solute at a given temperature than is in the solution Ex.: making koolaid 3. Supersaturated: contains more solute than a saturated one at the same temperature (See pg. 721)

Particles in Solution ► Why are electrolytes used in sports drinks and batteries????? ► An electrolyte is a solution that contains ions that conduct electricity in water. ► Your body works on electrical impulses. ► The sports drinks have sodium ions and potassium ions that transport signals in the body. ► Batteries contain ammonium ions, sulfate ions, and hydrogen ions that conduct electricity in the battery.

Effects of Solute Particles ► All solute particles affect the physical properties of the solvent, such as freezing point and boiling point. ► Why do we put “antifreeze” in our cars in the winter? ► Well, why do we put “antifreeze” in our cars in the summer? ► How can one substance keep your radiator from freezing up and from overheating?

Lowering Freezing Point ► By adding antifreeze to your radiator, it lowers the freezing point of the water in the radiator. HOW? 1. When a substance freezes, its particles arrange themselves in an orderly pattern. 2. The antifreeze adds solute particles that interfere with the formation of this pattern and “get in the way”, making it harder for the solvent to freeze. 3. The temp. has to be much colder before all the water freezes. See Figure 20 on page 725.

Raising Boiling Point ► By adding antifreeze to your radiator, you can also raise the boiling point and prevent overheating! 1. Evaporation occurs on the surface of a liquid. As the temperature increases, the movement of the molecules increases and leave the surface as a gas. 2. By adding antifreeze, the solute particles in the antifreeze “get in the way” and prevent as many water molecules from getting to the surface and evaporating. (See Figure 21 on pg. 726.) 3. As a result, the temperature has to be HIGHER before the water can all evaporate.

So………………………. ► Antifreeze particles “get in the way” and prevent the water from freezing at 0 0 C. It must be COLDER for the water to freeze. ► Antifreeze particles also “get in the way” and prevent the water from evaporating at C. It must be much HOTTER for all the water to evaporate.

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

► How Does It Work: ► What does the salt do? Just like we use salt on icy roads in the winter, salt mixed with ice in this case also causes the ice to melt. When salt comes into contact with ice, the freezing point of the ice is lowered. ► The lowering of the freezing point depends on the amount of salt added. The more salt added, the lower the temperature will be before the salt- water solution freezes. For example, water will normally freeze at 32 degrees F. A 10% salt solution freezes at 20 degrees F, and a 20% solution freezes at 2 degrees F.

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