Physical Science
Solutions
1.
Explain the 3 ways substances can
dissolve.
2.
Explain solubility.
3.
What ion do acids release?
4.
What is an electrolyte?
1.
Explain the 3 ways substances can
dissolve.
2.
Explain solubility
3.
What ion do acids release?
4.
What is an electrolyte?
What is an indicator?
 What happened in the demo when the
indictor and the base, ammonia, came in
contact?
 Explain what happens when acids and
bases are mixed? What is the term?


What type of reaction is it when copper
replaces the iron in an iron nail?
Fe(s) + CuSO4(aq) --> FeSO4(aq) + Cu(s)

What does the (s) and (aq) mean in the
above reaction equation?
Explain what you know about Acids and
Bases.
 Put your name on your October Bell
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 Review
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.
A mixture of flour & water
suspension
Colloidal
dispersion
solution
Colloidal dispersion
spreads the light out
Solvents and Solutes
Solvent – the part of the solution that is
present in the largest amount
 Solute – the part of the solution present in
the least amount

Parts of a Solution
Solutes and Solvents Video Clip

http://videos.howstuffworks.com/hsw/246
64-mixtures-solutes-and-solventsvideo.htm
Types of Solutions

Solutions can be made from different
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 solution

Solute particles are separated from each other and are surrounded by
solvent particles.
– a. Water is polar and easily dissolves ionic compounds i.e. NaCl
– b. Water can also dissolve many “nonpolar” particles because these
particles may have a slight polar side of the molecule which allows
the polar water to be attracted to 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+ + ClNotice that there are NO ions in the reactants, but that
IONS are formed in the products.
Animation showing hydrogen chloride gas
dissolved in water
Section 8.1
Comparing and Contrasting
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 Solvent:

Increased concentrations of solute in a solution will lower the
freezing point and increase the boiling point of the pure solvent
i. Salt spread over icy roads to melt the ice and turn it into water
ii. Salt placed into cooking water will increase the temperature of
the water before it starts to boil, i.e. decreasing cooking time of
pasta 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!
Figure 7
Factors
Affecting Rates
of Dissolving
Figure 7
Factors
Affecting Rates
of Dissolving
Factors
Affecting Rates
of Dissolving
Figure 7
Factors
Affecting Rates
of Dissolving
Figure 7
How Stuff Works Solutions
Video Clip

http://videos.howstuffworks.com/hsw/121
28-chemical-reactions-solutions-video.htm
Concentration – amount of
solute present
Concentrated – strong solution “more” solute present
 Dilute – weak solution “less” solute present

Solubility

Solubility – the amount of solute that will dissolve in a solvent at a given
temperature.
–
–
1. Higher temperatures will allow more of a solid to dissolve into a liquid
2. Higher temperatures will hold less gas in solution than colder temperatures
3 types of solutions based on solubility:
 1. Saturated – point when no more solute can dissolve into the solvent at
the given temperature (any additional solute won’t dissolve)
 2. Unsaturated Solutions - have less than the maximum amount of solute
Solubility

3. Supersaturated – contains more solute than it can normally
hold at a given temperature.
Factors Affecting Solubility

Polar and nonpolar solvents
– (like dissolves like, so polar and nonpolar
don’t usually mix)

Temperature
– Solubility increases as temperature increases
(when solids dissolve in liquids).
– Note that gases usually become less soluble
as the temperature of the solvent increases.

Pressure
– Increasing the pressure of a gas increases its
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
Cup
Solute
Amount
Solvent
Amount
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
Color
Intensity
Rating
1.
2.
3.
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.
Describe the relationship between the
amount of solute contained in the
solution and the color intensity of the
solution.
Are there any exceptions to the
relationship you observed? Explain




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
150
140
KI
130
120
110
NaNO3
100
grams solute per 100 grams H2O

Reading a Solubility
Curve Chart
90
KNO3
80
70
NH4Cl
NH3
60
50
KCl
40
NaCl
30
20
KClO3
10
Ce2(SO4)3
0
0
10
20
30
40
50
60
Tem perature/Celsuis
70
80
90
100
Do Solubility Curve wkst in
groups!!
Acids and Bases

Witch’s Brew Demo
The Dissociation of water
Water 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 Acids

Properties of Acids – compounds that:
– Release free Hydrogen ions into solution (H+)
– Reacts with metals and carbonates
– Turns blue litmus paper red
– Tastes sour (never taste)
– Are corrosive, eating away
Properties of Bases
–
–
–
–
–
–
i. Bases are compounds that:
1. Release hydroxide ions (OH-) into solution
ii. Has a bitter taste (never taste any solution unless told to do so)
iii. feels slippery
iv. Reacts with indicators like litmus by turning red litmus blue
v. has a pH greater than 7.0
Acids and Bases in Solution

Acids in Solution
– Acids are made of a H+ ion and an Anion (a
negatively charged ion)
– In water, acids dissociate (breakdown) into H+
and anions
 1. HCl  H+ + Cl-

Bases in solution
– Most bases release hydroxide ions into the
water
 1. NaOH  Na+ + OH 2. NH3 + H2O  NH4 + OH-
Acid / Base Reactions

When Acids and Bases are combined a
Neutralization reaction produces water
and a salt
– 1. Hydrochloric Acid and Sodium Hydroxide
yields water and Sodium Chloride
 a. HCl + NaOH  H2O + NaCl
 B. H+ + Cl- + Na+ + OH-  H2O + NaCl
– 2. Salt is an ionic compound formed from an
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 concentration
Which 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?

A base with a pH of 8 vs. 12?

An acid with a pH of 6 vs. 2?

An acid with a pH of 5 vs. a base with a
pH of 9?
Figure 15
Common Acids and Their Uses
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
Figure 17
Common Bases and Their Uses
Aluminum hydroxide
Al(OH)3
Deodorant, antacid
Calcium hydroxide
Ca(OH)2
Concrete, plaster
Magnesium hydroxide Mg(OH)2
Antacid, laxative
Sodium hydroxide
Drain cleaner, soap production
NaOH
Figure 19
Common Salts and Their Uses
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 sodium
Potassium 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
Section 8.4
Comparing and Contrasting
a. ionizes almost completely when dissolved in water
b. is a strong electrolyte
c. dissociates almost completely when dissolved in water