Interactions of Matter Notes Chapter 22: Solutions
I. How Solutions Form
a. What is a solution?—a solution is a mixture that has the same composition, color, density, and even taste throughout…a completely homogeneous mixture.
b. Solutes and Solvents—one substance is dissolved in another. The substance being dissolved is the solute. The substance that is doing the dissolving is the solvent. Usually the substance present in larger amounts is the solute. For salt dissolved in water, salt is the solute and water is the solvent. For CO2 gas dissolved in water, CO2 is the solute and water is the solvent.
i. Nonliquid solutions—not all solutions are liquids. Solids can be solutions. Gases can be solutions. Sterling silver is 92.5% silver and 7.5% copper. Brass is a solution of copper and zinc. Solid solutions are called alloys. Most coins are alloys.
c. How substances dissolve—dissolving of a solid in a liquid occurs at the surface of the solid. Like dissolves like. Polar things dissolve polar things. Nonpolar things dissolve nonpolar things.
i. How it happens—dissolving sugar. Sugar molecules are polar. The positive ends of the sugar attract the negative end of water molecules that surround it. As water molecules surround the sugar molecules, the sugar molecule is completely separated from the crystal.
ii. Dissolving liquids and gases—more complex, similar process. Gases in liquids move freely.
iii. Dissolving solids in solids—solid particles do move a little bit…not freely. Solids are usually melted, mixed, then solidified by cooling.
d. Rate of dissolving—Substances for solutions at a rate…some more quickly than others. Several things will affect how quickly something dissolves. –stirring, reducing crystal size (crushing), increasing temperature.
i. Stirring—causes the solute to more quickly come in contact with fresh solvent. ii. Crystal size—greatly increases the surface area. Since dissolving happens at
iii. Temperature—increasing temp speeds up the movement of particles. This way more solvent particles bump into solute particles at a faster pace.
iv. Controlling the process—by combining these techniques you can control how quickly or slowly something dissolves. Combining all three techniques will help something dissolve the fastest. Or by inhibiting each technique, dissolving can be slow…time release medicines do this.
Self Check p. Answers: 1) possible answer: liquid/liquid, solid/liquid, gas/liquid, gas/gas, solid/solid 2)Increasing temperature causes particles to move faster which causes solutes to dissolve faster 3) Metals are melted, mixed evenly, then cooled to form a solid; 4) Yes, one metal acts as the solute which the other metal acts as a solvent. 5) 7cm2; 6) 8.5% increase
II. Solubility and Concentration a. How much can dissolve?
i. Comparing solubilities—solubility is the maximum amount of solute that can be dissolve in a given amount of solvent at a given temperature. The solubility of a substance depends on the nature of the solute and the solvent. A solute is more soluble than another solute if more of it can be dissolved in the same amount of solvent at the same temperature.
1. Idea: What’s more soluble? Sugar or salt. What do you predict? How will we know?
b. Concentration—concentration refers to the amount of something that is dissolved in something else. A concentrated solution has more solute dissolve in solution than a dilute solution. The word ‘dilute’ refers to a solution that does not have a lot of solute in solvent.
i. Precise concentrations—The words “concentrated” and “dilute” are not precise terms. Solutions can be described precisely like this: 10 % fruit juice means 10% fruit juice and 90 % solvent. If you made 100mL of fruit juice at a concentration of 10%, you will have 10 mL of fruit juice and 90 mL of water.
c. Types of
Solutions--i. Saturated solutions—a solution that contains all the solute it can hold at a given temperature. If you increase the temperature, more solute can dissolve.
iii. Unsaturated solutions—“unsaturated” describes a solution that is able to dissolve more solvent.
iv. Supersaturated solutions—“supersaturated” describes a solution that has more solvent dissolved than is capable of being dissolve at a given temperature. This is an unstable situation that usually occurs then a saturated solution at high temperature is cooled to a lower temperature very carefully. A tiny stimulus like a tap on the container holding the solution, could cause it to rapidly crystallize. v. Solution energy—energy can be given off as a solute crystallizes. Also,
sometimes, energy is required as a solute dissolves. Supersaturated solutions of sodium acetate are used as hot packs. As they solution crystallizes, the heat released can be use to heat baby bottles and cold hands. Likewise, the dissolving of ammonium nitrate in water takes energy from the water. The cooling action is used to treat minor injuries that need cooling to reduce swelling.
d. Solubilities of gases—shaking or pouring a gas dissolved in a solvent causes more of the dissolve gas particles to reach the surface of the liquid.
i. Pressure effects—Increasing pressure cause more gas to dissolve in a liquid. Soda is bottled under high pressure causing more gas to dissolve. The cap keeps the pressure high, so the CO2 stays dissolved.
ii. Temperature effects—Cooling a liquid also causes more gas to be dissolved. When a soda is cooled, the CO2 stays in the solution longer. If you open a hot soda, the CO2 will rush out more quickly.
Self Check p. Answers: 1) No; you can find out how much solute dissolves in something by doing experiments to see. 2) 203.9 g; 3) solute z 4)unsaturated; 5) by staying capped, CO2 stays in solution longer, keeping it “fizzy”. 6) Making it is cheaper. If you were making 1,500 mL of orange dirnk you would need 150 mL of orange juice @ $1.49/1,500mL= 14.9 cents per 150 mL; 150mL of syrup @ 1.69/1,500mL = 16.9 cents per 150mL. So, to make 1,500 mL of drink you need only 14.9 + 16.9 cents = 31.8 cents of ingredients per 1,500mL of drink.
III. Particles in a Solution
i. Ionization—when compounds made of neutral atoms (like HCl) form charged particles, ionization occurs. For example:
HCl + H2O H3O1+ +
Cl1-ii. Dissociation—when compounds made of ions (ionic compounds) separate in water. Example. NaCl is an ionic compound made of Na1+ and Cl1- ions. When in water, the negative part of the water molecule is attracted to the positive part of the NaCl compound (the sodium is the positive part…AKA the cation). The negative part of the water molecule is attracted to the negative ion (the Cl1-anion). The NaCl is split apart. The ions move freely in the solution and the solution can conduct electricity.
b. Effects of Solute Particles—solute particles will affect the physical properties of the solvent that they are in.
i. Lowering of freezing point—solute particles decrease freezing point. When something freezes, the particles will orient themselves into orderly patterns called crystals. Crystals form when the order is established. When the pattern is disrupted by a solute, the crystals need to get to a much lower temperature to form.
ii. Animal antifreeze—animals have chemicals in their bodies that help them withstand freezing. Fish have glycoprotein. We put ethylene glycol in our car radiators to keep the water from freezing.
iii. Raising of boiling point—solute particles can also get in the way of evaporating particles when temperature increases. In other words, the temperature of a solution needs to be higher than if the liquid were pure.
iv. Car radiators—antifreeze has two benefits, lowering the freezing point and increasing the boiling point.
Chapter 23: Acids, Bases, and Salts I. Acids and Bases
a. Acids
i. Properties of acids—an acid is a substance that produces hydrogen ions in solution. The hydrogen ions interact with water molecules (H2O) to make an
special ion called a hydronium ion (H3O1+)
1. They taste sour (many should not be tasted), acids are corrosive, some acids react with metal (eating away at the metal as they produce a gas), acids react with indicators in a predictable way.
2. Indicators are organic compounds that change color when they come in contact with an acid or a base. The indicator, litmus paper, turns red in the presence of acid.
ii. Common acids—our textbook mentions some important acids that we eat and several that are used in various industries.
b. Bases—we don’t eat too many bases—baking powder is a base, amines in some foods are bases. Soap is basic. They feel slippery, they are used in cleaning, and have industrial uses. A base is any substance that form hydroxide ions (OH-) in water. Another way to say it is that a base accepts H+ ions from acids forming H2O.
i. Properties of bases—bases can be considered the opposite of acids. They are slippery, they are bitter tasting. Bases can be corrosive. Bases react with indicators. Litmus paper turns blue in the presence of a base.
ii. Common bases—usually found in cleaning products (table shows some and their uses)
c. Solutions of Acids and Bases
i. Dissociation of Acids—acids dissociate in water. The dissociated H+ ion interacts with water to produce hydronium ions. This is why acid reactions are considered ionization reactions because new ions are generated in the water. ii. Dissociation of Bases—bases also dissociate in water. They produce OH- ions
that do not generally interact with water. Unlike the H+ ion in acids, the OH- ion
does not interact with water to produce a new ion.
iii. Ammonia—a special base, is NH3. When NH3 reacts with water, it causes water
to form OH- ions and an NH4+1 ion. This seems like an ionization reaction to Mr.
should never be placed near cleaners that contain chlorine (sodium
hypochlorite). The resulting gases, hydrazine and chloramines can permanently damage lung tissue.
Self Check p. 701 Answers: 1) all reasonable responses are accepted; 2) an organic compound that changes color in acid or base; 3) magnesium sulfate; 4) water; HOH; 5) acetic acid is organic. It has a COOH group; 6) 180.16 g/mol.
II. Strengths of Acids and Bases
a. Strong and Weak Acids and Bases—strong acids completely dissociate in water. Examples: HCl, HNO3, H2SO4. Weak acids do not dissolve completely in water. Examples:
acetic acid (vinegar) and carbonic acid. Weak acids do not conduct as much electricity as strong acids.
i. Strong and Weak Acids—equations for strong acids have one way arrows: HCl (g) + H2O (l) H3O+(aq)+ Cl- (aq)
Because almost all of the acid particles dissolve, the arrow always points to the products. In contrast, weak acids partially dissociate. These equations use two way arrows:
CH3COOH (l) + H2O (l) ↔ H3O+(aq) + CH3COO- (aq)
ii. Strong and Weak Bases—a strong base dissociates completely, a weak base does not completely dissociate in a situation completely analogous to the strong acids and base equation written above.
iii. Strength and concentration—try to not get confused between strong acids and strong bases and concentrated solutions and dilute solutions. Strength of acids and bases only refers to the ability for acids and bases to dissociate, not the concentration. For this reason, it is possible to have a dilute solution of a strong acid or base. Conversely, it is possible to have a concentrated solution of a weak acid or base.
b. pH of a Solution—pH is a measure of the concentration of H+ . The greater the H+ ion
concentration the lower the pH. In other words, the more concentrated an acid solution is the lower the pH. Because neutral water has an equal concentration of H+ and OH- ions, the pH is 7. The maximum pH possible is pH 14…a high concentration of OH- ions. At 25oC, pure water will have a pH of 7. Universal pH indicator paper can be used to
c. Blood pH—the pH of your blood contains buffer that help keep the pH within a narrow range. Sensors in your brain, measure pH and tell your body to start breathing harder and faster to remove excess carbonic acid from your blood.
Self Check p. 705 Answers: 1) The strength of an acid is determined by its ability to produce H+ ions in solution. The strength of a base is determined by its ability to produce OH- ions in solution 2) You can dilute a strong acid by adding a small amount of acid to a large amount of water; 3) an ionic compound breaks into ions, which conduct electricity; 4) 9.1 basic, 1.2 very acidic, 5.7 acidic; 5) for a pH of 8.2 add HCl to lower it, for a pH of 6.9 add Na2CO3 to raise the pH. 6) 100 times more acidic.
III. Salts
a. Neutralization—a chemical reaction between an acid and a base that takes place in a water solution. The acid and base are neutralized, the result is an aqueous salt and water.
H3O+ (aq) + OH- 2H2O (l)
HCl + NaOH NaCl + H2O
i. Salt formation—a salt isa compound formed when the negative ions from an acid combine with the positive ions from a base.
ii. Acid-base reactions—acid + base salt + water
b. Salts—there are many salts…most living creatures need NaCl to live. Yum.
c. Titration—a titration is a method for determining how concentrated an acid or a base is. Titrations are performed by slowly adding acid or base to a solution with indicator added. The titration comes to an end point when the solution is neutral. You know you have reached a neutral solution when you reach the reference color for neutral for the indicator.
d. Soaps and Detergents (unassigned) e. Versatile Esters (unassigned)
Self Check p. 715 Answers: 1) a neutralization reaction is a reaction between an acid and a base. The result is a salt (ionic compound in solution) and water. 2) the indicator changes color when the substance of unknown concentration has completely reacted with the substance of known
(Al2(CO3)3); 6) one molecule of base reacts with two molecules of acid. . For molecules of HCl are needed to produce four molecules of water.
(As mentioned in the unit helper, in the interest of time and other important factors, we will not discuss chapter 24 in detail. During various times this year, students have been presented with concepts from this chapter. Students may wish to read the material in this section for the benefit of the end of course exam in physical science.)
Chapter 24: Organic Compounds I. Simple Organic Compounds Self Check p. Answers: 1)
II. Other Organic Compounds Self Check p. Answers: 1)
III. Petroleum—A Source of Other Compounds Self Check p. Answers: 1)
