Physical Physical ScienceScience

Solutions

1.1. Explain the 3 ways substances can Explain the 3 ways substances can dissolve.dissolve.

2.2. Explain solubility.Explain solubility.

3.3. What ion do acids release?What ion do acids release?

4.4. What is an electrolyte?What is an electrolyte?

1.1. Explain the 3 ways substances can Explain the 3 ways substances can dissolve.dissolve.

2.2. Explain solubilityExplain solubility

3.3. What ion do acids release? What ion do acids release?

4.4. What is an electrolyte?What is an electrolyte?

What is an indicator?What is an indicator? What happened in the demo when What happened in the demo when

the indictor and the base, ammonia, the indictor and the base, ammonia, came in contact?came in contact?

Explain what happens when acids Explain what happens when acids and bases are mixed? What is the and bases are mixed? What is the term?term?

What type of reaction is it when copper What type of reaction is it when copper replaces the iron in an iron nail?replaces the iron in an iron nail?

FeFe(s) + CuSO4(aq) --> FeSO4(aq) + (s) + CuSO4(aq) --> FeSO4(aq) + CuCu(s)(s)

What does the (s) and (aq) mean in What does the (s) and (aq) mean in the above reaction equation?the above reaction equation?

Explain what you know about Acids Explain what you know about Acids and Bases.and Bases.

Put your name on your October Bell Put your name on your October Bell Ringers and prepare to turn them in.Ringers and prepare to turn them in.

Salt Water vs. Regular Water

Which will freeze at a lower temperature?

What is a solution?

A mixture of two substances that have physically combined!!!

Solutions and Suspensions ReviewSolutions and Suspensions Review

A mixture of flour & water

suspension

Colloidal dispersion solution

Suspension - the particles are temporarily suspended in the liquid & are large enough to collectively make the material appear cloudy. They will settle out after a while.

Colloidal dispersion - very small particles spread throughout the liquid which are large enough to reflect light, but not large enough to be seen individually. It may look either clear or cloudy in ordinary room light. The particles in a colloidal dispersion remain dispersed in the liquid and will not settle out.

Solution - will appear clear even when a light is shown through it. The particles are completely dissolved & never settle out.

Colloidal dispersion spreads the light out

Solvents and SolutesSolvents and Solutes SolventSolvent – the part of the solution that – the part of the solution that

is present in the largest amountis present in the largest amount SoluteSolute – the part of the solution – the part of the solution

present in the least amountpresent in the least amount

Parts of a SolutionParts of a Solution

Solutes and Solvents Video Solutes and Solvents Video ClipClip

http://videos.howstuffworks.com/hsw/24664-mixtures-solutes-and-solvents-video.htm

Types of SolutionsTypes of Solutions Solutions can be made from different Solutions can be made from different

states of matter:states of matter:

Dissolving

A solute dissolves into a solvent, normally water.

In order for a solution to form, the attractions that hold the solute together and the solvent together must be overcome.

Particles in solutionParticles in solution Solute particles are separated from each other and are Solute particles are separated from each other and are

surrounded by solvent particles.surrounded by solvent particles.– a. a. Water is polarWater is polar and easily dissolves ionic compounds i.e. and easily dissolves ionic compounds i.e.

NaClNaCl– b. Water can also dissolve many “nonpolar” particles b. Water can also dissolve many “nonpolar” particles

because these particles may have a slight polar side of the because these particles may have a slight polar side of the molecule which allows the polar water to be attracted to molecule which allows the polar water to be attracted to these surfaces.these surfaces.

Because of its polarity, water is the “universal solvent”

3 ways to dissolve:

1. dissociation of Ionic compounds An ionic compound separates into ions as it

dissolves Example – NaCl in water This is a PHYSICAL change!

3 ways to dissolve:

2. dispersion of molecular compounds

Breaking into small pieces Example – sugar dissolving in water

– Both are polar molecules so they attract one another

This is a PHYSICAL change!!

3 ways to dissolve: 3. ionization of molecular compounds

When neutral molecules gain or lose electrons

Example – hydrogen chloride gas and water This is a CHEMICAL change!

H20 + HCl H3O+ + Cl-

Notice that there are NO ions in the reactants, but that IONS are formed in the products.

Animation showing hydrogen chloride gas dissolved in water

Comparing and Contrasting

Section 8.1

a. and b. Physical change and ions are present before and after.

c. and d. Chemical change and ions are present after, but not before.

Properties of Solutions More Conductive

– NaCl dissociates in water, so the ions conduct electricity

Freezing Points are lower– That’s why we add salt to roads in the

winter

– MgCl2 dissociates and the Mg and Cl ions are attracted to the water molecules and interrupt the freezing process

– This changes the freezing point from 0 to -15 degrees Celsius

Properties of Solutions

Boiling Points are higher than normal– Solutes can raise the boiling points of solvents– Coolant in car radiators is a solution of water

and ethylene glycol (C2H6O2).– At what temperature does water normally boil?– Adding ethylene glycol raises the boiling point– So, does your engine normally overheat on a

hot day?– Would you think ethylene glycol would lower

the freezing point of water?

Effects of Solutes on the Effects of Solutes on the Solvent:Solvent: Increased Increased concentrations of solute in a solution will concentrations of solute in a solution will lower the freezing lower the freezing

pointpoint and and increase the boiling point increase the boiling point of the pure solventof the pure solvent

i. Salt spread over icy roads to melt the ice and turn it into waterii. Salt placed into cooking water will increase the temperature ofthe water before it starts to boil, i.e. decreasing cooking time ofpasta as it cooks in hotter water.

Properties of Liquid Solutions Demo – Let’s look at the

results!!! Materials – 2 trays with sides at least 2 inches deep, ice, rock salt, water, 2 clear plastic containers, thermometer

Will water in an ice bath remain at 0 degrees Celsius as long as the ice still remains?

Will salt lower the temperature of the water?– Fill both trays with ice to a depth of 2 inches– Add rock salt to the ice of one of the trays.– Add water to both trays to a depth of 1 inch.– Add 1-2 inches of water to each plastic

container and place each in an ice bath. – Check temperatures and add more ice as

necessary throughout the class period. What happens to each container of water?

Properties of Liquid Solutions Demo

Doesn’t this seem like a contradiction? You can use Rock salt for fast cooling but also for melting ice and

snow… Why? Salt makes ice melt faster, and drops the temperature to that of

freezing salt water. The heat used to melt the ice is drawn much faster from the surroundings. Since the surroundings lose large quantities of heat to the ice, they cool rapidly and continue to cool until they reach the freezing temperature of melting saltwater ice. This temperature is below the mixture’s freezing point.

Salt dissolving in water is considered an "endothermic" reaction (it absorbs heat), making the water/salt solution (brine) colder as it happens, and helping the ice cream ingredients to freeze into something yummy.

Tray with Ice only was 0 degrees Celsius. Container of water was 2 degrees.

Tray with Ice and Rock Salt was -6 degrees Celsius. Container of water was 1 degree. The plastic container actually froze along the bottom!!!

So, the tray with the ice and rock salt absorbed the heat from the container of water and made it freeze!!!

When salt is used on roads, the slushy stuff is COLDER than 0 degrees!!

Salt Water vs. Regular Water

Which will freeze at a lower temperature?

What happened?

Properties of Solutions Heat of Solution

– During the formation of a solution, energy is either released or absorbed, so the reaction can be endothermic or exothermic!

– Examples: Cold Packs and Heat Packs

– Hot Ice Video Clip

How to make Hot Ice

Rates of Dissolving

Factors Affecting Rates of Dissolving

Surface area– The greater the surface area of the solute, the

greater the collisions between solute and solvent molecules.

Stirring– Allows for more collisions because it moves

dissolved particles away from surface of the solid

Temperature– Allows for more collisions because you speed up

the molecules!

Factors Affecting

Rates of Dissolving

Figure 7

Factors Affecting

Rates of Dissolving

Figure 7

Factors Affecting

Rates of Dissolving

Figure 7

Factors Affecting

Rates of Dissolving

Figure 7

How Stuff Works Solutions How Stuff Works Solutions Video ClipVideo Clip

http://videos.howstuffworks.com/http://videos.howstuffworks.com/hsw/12128-chemical-reactions-hsw/12128-chemical-reactions-solutions-video.htmsolutions-video.htm

Concentration – amount of Concentration – amount of solute presentsolute present

ConcentratedConcentrated – strong solution “more” solute present – strong solution “more” solute present Dilute Dilute – weak solution “less” solute present– weak solution “less” solute present

SolubilitySolubility SolubilitySolubility – the amount of solute that will dissolve in a solvent at a given – the amount of solute that will dissolve in a solvent at a given

temperature. temperature. – 1. Higher temperatures will allow more of a solid to dissolve into a liquid1. Higher temperatures will allow more of a solid to dissolve into a liquid– 2. Higher temperatures will hold less gas in solution than colder temperatures2. Higher temperatures will hold less gas in solution than colder temperatures

3 types of solutions based on solubility:3 types of solutions based on solubility: 1. Saturated1. Saturated – point when no more solute can dissolve into the solvent at – point when no more solute can dissolve into the solvent at

the given temperature (any additional solute won’t dissolve)the given temperature (any additional solute won’t dissolve) 2. Unsaturated Solutions 2. Unsaturated Solutions - have less than the maximum amount of solute- have less than the maximum amount of solute

SolubilitySolubility 3. Supersaturated 3. Supersaturated – contains more solute than it can – contains more solute than it can

normally hold at a given temperature. normally hold at a given temperature.

Factors Affecting Solubility Factors Affecting Solubility Polar and nonpolar solventsPolar and nonpolar solvents

– (like dissolves like, so polar and nonpolar don’t (like dissolves like, so polar and nonpolar don’t usually mix)usually mix)

TemperatureTemperature– Solubility increases as temperature increases Solubility increases as temperature increases

(when solids dissolve in liquids).(when solids dissolve in liquids).– Note that gases usually become less soluble as Note that gases usually become less soluble as

the temperature of the solvent increases.the temperature of the solvent increases. PressurePressure

– Increasing the pressure of a gas increases its Increasing the pressure of a gas increases its solubility in a liquid.solubility in a liquid.

a.the maximum amount of solute that dissolves in a given amount of solvent at a given temperature

b.What factors affect solubility? c. and d. How is the concentration of a solution expressed? percent by volume,

percent by mass, molarity

Solubility of Some Common Substances

If you add 40 g of salt to 100 g of water at 20 degrees and it dissolves, what type of solution would you have?

If you add 40 g of sugar to 100 g of water at 20 degrees and it dissolves, what type of solution would you have?

What type of solution do you have when you add 9.6 g of baking soda to 100 g of water at 20 degrees?

Solute Concentration Activity

You will be provided with five clear beakers, colored drink mix, measuring spoons, and water. Copy the table below onto a piece of paper. Label the beakers 1–5. In each of the beakers, dissolve the given amounts of solute into the corresponding amounts of solvent according to the table.

Solute Concentration Activity

CupSolute Amount

Solvent Amount

Color Intensity Rating

1 ½ teaspoon 200 mL

2 1 teaspoon 200 mL

3 2 teaspoons 200 mL

4 4 teaspoons 200 mL

5 1 teaspoon 100 mL

1. Rate each solution with a number 1–4 that corresponds to the intensity of its color (1 = least intense, 4 = most intense). In the table, fill in the color intensity rating for each solution.

2. Describe the relationship between the amount of solute contained in the solution and the color intensity of the solution.

3. Are there any exceptions to the relationship you observed? Explain

Reading a Solubility Curve Chart

The curve shows the # of grams of solute in a saturated solution containing 100 mL or 100 g of water at a certain temperature.

Solutes whose curves move upward w/ increased temperature are typically solids b/c the solubility of solids increases w/ increased temperature.

Solutes whose curves move downward w/ increased temperature are typically gases b/c the solubility of gases decreases with increased temperature

Any amount of solute below the line indicates the solution is unsaturated at a certain temperature

Any amount of solute above the line in which all of the solute has dissolved shows the solution is supersaturated.

Solubility Curves of Pure Substances

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0 10 20 30 40 50 60 70 80 90 100

Temperature/Celsuis

gra

ms

solu

te p

er 1

00 g

ram

s H

2O

KI

NaNO3

KNO3

Ce2(SO4)3

NH3

KClO3

NH4Cl

KCl

NaCl

Do Solubility Curve wkst in Do Solubility Curve wkst in groups!!groups!!

Acids and Bases

Witch’s Brew Demo

The Dissociation of waterWater can actually “dissolve” itself by pulling a proton (Hydrogen atom w/out its electron) off of one water molecule

When proton can be transferred from one water molecule to another, resulting in the formation of one hydroxide ion (OH-) and one hydronium ion (H3O+).

It will often do the reverse, change a hydronium ion & an hydroxide ion back into water. The equation goes both ways until equilibrium is found.

When equilibrium is reached and Hydronium ions = Hydroxide ions

the solution is NEUTRAL

Properties of AcidsProperties of Acids Properties of Acids – compounds that:Properties of Acids – compounds that:

– Release free Hydrogen ions into solution (H+)Release free Hydrogen ions into solution (H+)– Reacts with metals and carbonatesReacts with metals and carbonates– Turns blue litmus paper redTurns blue litmus paper red– Tastes sour (never taste)Tastes sour (never taste)– Are corrosive, eating awayAre corrosive, eating away

Properties of BasesProperties of Bases– i. Bases are compounds that:i. Bases are compounds that:– 1. Release hydroxide ions (OH-) into solution1. Release hydroxide ions (OH-) into solution– ii. Has a bitter taste (never taste any solution unless told to do so)ii. Has a bitter taste (never taste any solution unless told to do so)– iii. feels slipperyiii. feels slippery– iv. Reacts with indicators like litmus by turning red litmus blueiv. Reacts with indicators like litmus by turning red litmus blue– v. has a pH greater than 7.0v. has a pH greater than 7.0

Acids and Bases in SolutionAcids and Bases in Solution Acids in SolutionAcids in Solution

– Acids are made of a HAcids are made of a H++ ion and an Anion (a negatively ion and an Anion (a negatively charged ion)charged ion)

– In water, acids dissociate (breakdown) into H+ and anionsIn water, acids dissociate (breakdown) into H+ and anions 1. HCl 1. HCl HH++ + Cl + Cl--

Bases in solutionBases in solution– Most bases release hydroxide ions into the waterMost bases release hydroxide ions into the water

1. NaOH 1. NaOH NaNa++ + OH + OH--

2. NH2. NH33 + H + H22O O NHNH44 + OH + OH--

Acid / Base ReactionsAcid / Base Reactions When Acids and Bases are combined a When Acids and Bases are combined a

NeutralizationNeutralization reaction produces water reaction produces water and a saltand a salt– 1. Hydrochloric Acid and Sodium Hydroxide 1. Hydrochloric Acid and Sodium Hydroxide

yields water and Sodium Chlorideyields water and Sodium Chloride a. HCl + NaOH a. HCl + NaOH HH22O + NaClO + NaCl

B. HB. H++ + Cl + Cl-- + Na + Na++ + OH + OH-- H H22O + NaClO + NaCl

– 2. Salt is an ionic compound formed from an 2. Salt is an ionic compound formed from an acid / base reaction (neutralization)acid / base reaction (neutralization)

pH Scale

0-14: <7 acid, >7 base, 7 neutral Strong Acids and Bases- ionize

almost completely in water Weak Acids and Bases- ionize slightly

in water Used as Buffers- which resist large

changes in pH Electrolytes- ionizes completely in

water, conducts an electric current

b.a compound that produces hydronium ions when dissolved in water

d.a compound that produces hydroxide ions when dissolved in water

f. any ionic compound that forms when an acid reacts with a base

The pH Scale

Figure 22

Hydrogen ion concentrationWhich is stronger: an acid with a pH of 2 or a pH of 4?

A pH of 1 has ten times as many hydrogen ions as a pH of 2, 100 times as many as a pH of 3, and 1000 times as many as a pH of 4.

Which is stronger/weaker?Which is stronger/weaker?

A base with a pH of 8 vs. 12?A base with a pH of 8 vs. 12?

An acid with a pH of 6 vs. 2?An acid with a pH of 6 vs. 2?

An acid with a pH of 5 vs. a base with An acid with a pH of 5 vs. a base with a pH of 9?a pH of 9?

Common Acids and Their UsesFigure 15

Acetic acid CH3COOH Vinegar

Carbonic acid H2CO3 Carbonated beverages

Hydrochloric acid HCI Digestive juices in stomach

Nitric acid HNO3 Fertilizer production

Phosphoric acid H3PO4 Fertilizer production

Sulfuric acid H2SO4 Car batteries

Common Bases and Their UsesFigure 17

Aluminum hydroxide Al(OH)3 Deodorant, antacid

Calcium hydroxide Ca(OH)2 Concrete, plaster

Magnesium hydroxide Mg(OH)2 Antacid, laxative

Sodium hydroxide NaOH Drain cleaner, soap production

Common Salts and Their UsesFigure 19

Sodium chloride NaCl Food flavoring, preservative

Sodium carbonate Na2CO3 Used to make glass

Potassium chloride KCl Used as a salt substitute to reduce dietary intake of

sodiumPotassium iodide Kl Added to table salt to

prevent iodine deficiency

Magnesium chloride MgCl2 De-icer for roads

Calcium carbonate CaCO3 Chalk, marble floors, and tables

Ammonium nitrate NH4NO3 Fertilizer, cold packs

Comparing and Contrasting

Section 8.4

a. ionizes almost completely when dissolved in water

b. is a strong electrolyte

c. dissociates almost completely when dissolved in water