Do Now
• Take out your notes packet
• Identify the solute, solvent and solution for
hot chocolate
Solution: What is a solution?
Solute, solvent and solution
• The term ‘solution’ may be one you are familiar
with outside of chemistry, but the definition for it
in chemistry may be different than what you
thought. In chemistry a solution is defined as “A
homogeneous mixture formed from a solute
dissolved into a solvent”. Remember that
‘homogenous’ means that it has the same
consistency throughout the mixture. Solute and
solvent may be new terms for you as well. A
solute is what is being dissolved, and the solvent
is the one that is doing the dissolving. Most of the
time in class water will be our solvent.
• 2. Identify the solute, solvent and the solution
for a pitcher of kool-aid
•
Solute:____________
•
Solvent:________________
•
Solution:____________
What is happening when something is
dissolving?
• Using an example to answer this question will be
helpful. Let’s take a look at dissolving Sodium Chloride
(NaCl), table salt. Salt in the crystal form is really
organized and the ions are locked into place because of
their opposite charges. When these crystals are
introduced to water, which is polar, they begin to
interact. The positive ends of the polar water molecule
are attracted to the negative chloride ion. The negative
ends of the water are attracted to the positive sodium
ions. The water molecules begin to surround the
individual ions and tear them away from the other ions
in the crystal. These ions are kept separated from each
other by the water molecules
Simulator
• This may help
• Online version
Use the image on the previous page
to answer the following questions
• 1. How is the left and right image different from each
other?
• 2. What is the difference between how the water
molecules surround the Na+ ions and how they
surround the Cl- ions?
• 3. Let’s say all the water molecules were ‘busy’
separating the ions from each other. What would
happen if you added more salt?
c)
•
How much ‘stuff’ is dissolved:
Saturated, unsaturated and
supersaturated
There is a limit to how much solute (‘stuff’) a certain amount of solvent (usually
water) can dissolve. At a certain point the solution becomes saturated. An analogy
may help make sense of the term ‘saturated’. A sponge, like a solution, can only
hold so much ‘stuff’ before it cannot hold any more. When a sponge is saturated, it
can no longer hold any more water. When a solution becomes saturated, it can no
longer ‘hold’ (dissolve) any more ‘stuff’ (solute). If you were to add more solute it
would simply sink to the bottom of the solution as an undissolved solid. This
undissolved solute is called the precipitate, hence the saying: “If you aren’t part of
the solution, then you’re part of the precipitate!” (lol). If a solution has dissolved
as much solute as it can possibly hold, it is described as saturated. If it can still
dissolve more solute, then it is described as unsaturated. Sometimes solutions can
be ‘tricked’ into dissolving more solute than it should be able too. This is a special
condition referred to as supersaturated. Rock candy is made from making use of a
supersaturated solution of sugar and water. Carbonated water is another example.
The closed bottle forces more CO2 to dissolve in the water by increasing the
pressure. Once it is opened the CO2 slowly escapes as bubbles. This process can be
sped up by the addition of a nucleation site (such as ones found on a Mentos
candy). Remember, if it is supersaturated, all the ‘extra’ solute is actually dissolved,
and not sitting at the bottom of the solution.
Cool demo
• Supersaturated solution used as a heat pack
• Neat experiments using them
• What happens when salt water starts to
evaporate?
Where is the precipitate
OH NO!!!
Do Now
• Pick up a copy of the lab (for later) (due
Tuesday when we return)
• Take out your notes packet
• Try and come up with a way to remove the
permanent marker on the board with…
Factors affecting solubility; How can
we make more stuff dissolve?
• ‘Like dissolves like’: Why doesn’t water
and oil mix?
•
•
The first factor to be examined for how to make more stuff dissolve can be remembered with the
simple phrase ‘like dissolves like’. It refers to the polarity of a the solute and the solvent. If both are
polar or if both are nonpolar, then the solvent will dissolve the solute. If they are different (one
polar and the other nonpolar) then the solvent will not dissolve the solute. An example of this can
be seen when you mix oil with water. Water is polar, and oil is nonpolar. This will result in neither
dissolving into the other. You may have previously believed that oil and water didn’t mix because of
their different densities, but YOU WERE WRONG! They do not mix because they have different
polarities! The reason why the oil sits on top of the water is because it is the less dense of the two,
but the reason they don’t mix is because of the difference in polarities. PLEASE, correct your friends
and strangers alike from this point forth if they have this misunderstanding.
The idea of ‘like dissolves like’ can also be applied to permanent markers. They are considered
‘permanent’ because you would probably try to clean them with water. The pigments in the marker
are nonpolar, and water is polar. This means that when you try to clean the marker with water, the
water will not be able to dissolve it! If you were a clever science student, you would try a different,
nonpolar, solvent to clean it with (benzene or ethyl acetate AKA nail polish remover). PLEASE NOTE,
before you go marking stuff up, it works best on clean, non-porous surfaces. Also, using these
nonpolar solvents may also damage the thing you are trying to clean, so be careful…don’t ruin
anything!
Let me show you
• Water and oil in slow-mo
Temperature and pressure: Why does
soda go flat?
• Other factors that affect how much solute can dissolve in a solution are
temperature and pressure. Temperature can have different effects on
different types of solutes. For solid solutes, generally speaking, the higher
the temperature, the more solute can be dissolved. This can be seen with
salt and water. If you had some salt water with salt sitting undissolved at
the bottom, you could heat the water up and more salt would dissolve.
For gases, generally speaking, as temperature increases its solubility
decreases. Think about what happens to soda once it gets warm…it goes
flat. The water cannot hold as much carbon dioxide gas and it loses its fizz!
• - Pressure only affects gaseous solutes, and has no effect on solids. Gases
become more soluble with an increase in pressure. You can think of it as
the pressure is pushing more of the gas into the liquid. This is also why,
once you open the pressurized soda bottle, the gases start to bubble out,
there is now less pressure!
• On the axis to the side, draw a solid line showing the relationship between
temperature and solubility for solids, and a dashed line for gas.
Solid line =
solids
Dashed =
gases
Practice problems
• 1. Nuclear power plants produce a lot of
uncontaminated warm water which gets
dumped into rivers. Why would this be a
concern for the fishes that live in the water?
• 2. Scuba divers use pressurized tanks to store
air so that they can dive deep underwater and
still breath. The further down they go, the
greater the pressure there is on their body.
How would this affect the amount of air that
would dissolve into the divers body?
• 2b. OH NO! AN EMERGENCY! RISE! RISE! RISE!
A scuba diver experiences a problem and must
immediately surface after spending a bit of
time swimming very deep. What would
happen to the amount of gas that could be
dissolved in their blood when they surfaced?
2c. Why might this cause some issues
for the diver?
For the solutes below, If temperature is
If temperature is
If pressure is increased,
dissolved in water:
increased, the solubility decreased, the solubility the solubility of this
of this solute will:
of this solute will:
solute will:
NH3 (g)
KCl (s)
Draw the structures of the compounds Is the solute polar or Will this solute dissolve
If they are molecular.
nonpolar or ionic? in water or benzene?
CH4
H2S
Do Now
• Take out the quarterly review you picked up
on Friday
• Work on it
• Questions? Throw a hand up
Major Topics
• -Periodic table
• Organization of periodic table (atomic number, groups
vs. periods, principle energy levels, valence electrons)
• Chemical properties based on location on periodic
table
• Classifying elements on the PT (metals, nonmetals,
metalloids, noble gases) (you wont have your PT for
the quarterly)
• Calculating parts of the atoms (protons, neutrons,
electrons, mass etc..)
• Various models of the atom (Dalton, Bohr, etc..)
Major Topics
• Bonding:
• Determining types of bonds (END, metals and
nonmetals, etc.)
• Determine bond polarity
• Determining molecular polarity
• Calculating: gfm, converting to and from
moles, %composition
Major Topics
• Equations
• Balancing chemical equations
• Determining type of reaction based on
equation
• Stoichiometry: using balanced equations to
solve stoichiometry problems
How Mr. Donohue Would Study
• Read through each notes packet as a refresher
– Came across stuff I totally didn’t remember:
–
Rewrite it out “Periods go across = PEL”
• Redo the homework problems
– Cover the answers, check them
– Not sure what the answer is…
–
Do some research and find out the right
answer
• Retake the test(s) and see how I did
For right now
• I’ve put together some practice problems
• Do them, check the answers, consult a friend
then me if you can not figure out the right
answer
• Finished? Read over the notes packets, redo
the homework packets/tests. Keep studying
(20% of your grade is kind of a big deal)
Do now
• Pick up a copy of the lab and read it over
• Homework: Finish the lab
• Read the next topic in the notes
– C. Solubility Curves
• TEST Friday after regents week (start reading
the rest of the packet)
• DIDN’T TAKE LAST UNITS TEST: itll be a zero if
you don’t make it up…
Safety
•
•
•
•
Goggles
Pretty safe lab…don’t do anything silly
No rough housing
No squirting each other with water…
The Story
• Someone stole my Pez Dispenser!
• Luckily they left a ransom note
• The ink from the note will be analyzed and
compared to the pens found in the 4 suspects
offices
Big Idea
• Markers are a mixture of different pigments, some
of which are really polar and some of which are
really nonpolar
• This difference will be used to separate the
pigments
– Polar pigments will dissolve in and travel with the water
– Nonpolar pigments will stick to the nonpolar filter paper
• This will allow us to examine the pigments in
different pens and ID the pen used to write the
ransom note
GO DO IT!
• Homework: Finish the lab
• Read the Rest of the notes packet over the
next 9 days…
Do Now
• A bit-o-review
• Solute – Solvent – Solution…
• To increase solubility of a solid solute you
_________ temperature
• To increase solubility of a gaseous solute you
can ___________ temperature OR
__________ ______________
• CSI Lab due tomorrow
c)
Solubility curves
Go Ahead
and take
out your
RT + Notes
packet
c) Solubility curves
• Solubility curves show the solubility of different solutes in water at
different temperatures. The lines represent how much of that solute can
dissolve in 100. grams of water at the given temperatures. Don’t let the
unit ‘g solute/100.g H2O’ throw it off. Remember, if we used more water
we could dissolve more solute, therefore we need to pick a specific
amount of water used to dissolve the solute. 100. Grams is a nice round
number. If you used 200. grams of water instead, you would be able to
dissolve twice as much solute. If you used 50. g instead of 100 g, then you
could only dissolve half of the solute indicated on the graph.
• You also need to be able to use this chart to determine if a solution is
saturated, unsaturated or supersaturate. Remember, the lines represent
saturation, so if you were given a point and it fell directly on the line, then
that solution is saturated. If your point fell below the line, that means
more solute could be dissolved in the solution, making it unsaturated. If
your point fell above your line, then that solution is holding more solute
than it is supposed to be able to hold and is supersaturated.
• Example:
• How many grams
of NaNO3 are
required to make
a saturated
solution in 100 g
of water at 30oC?
• Start at 30oC,
move up to the
NaNO3 line.
Scoot across to
Solute (g).
• 96 grams can be
dissolved in 100 g
of water at 30oC.
• How many grams
of NaNO3 are
required to make a
saturated solution
in 50 g of water at
30oC?
• Since in the last
question, it was
determined that 96
grams of NaNO3 can
be dissolved in 100
g H2O, since 50 g is
half as much water,
only half as much
NaNO3 can be
dissolved.
Therefore, 96/2 =
48 g of NaNO3 can
be dissolved in 50 g
H2O.
• What is the
solubility of HCl
in 100 g of water
at 70oC?
•
• Start at 70oC, up
to HCl and
across: 52 g HCl
in 100 g H2O @
70oC
• What kind of
solution do you
have if 80 grams of
KClO3 are dissolved
in 100 g of water at
40oC?
• Start at 80 grams,
and 40oC. See
where the lines
intersect with
respect to the KClO3
line. They intersect
far above the KClO3
line. At 40oC, the
solubility of KClO3 is
only 16 grams in
100 g of water. This
solution is
supersaturated.
• For the above
solution, what can
you do with
temperature and
amount of KClO3 to
make the solution
saturated?
• If you want to
dissolve 80 g of
KClO3 in 100 grams
of water, the table
says you need to
heat the solution to
75oC (adding an
additional 35oC to
the current
temperature of
40oC).
Practice in the notes
• Your turn!
• 1) As the
temperature
decreases, the
solubility of
gases
• 2) As the
temperature
decreases, the
solubility of
solids in liquids
• 3) Which of the
salts on Table G is
the least soluble
at 90oC
• 4) Which gas on
Table G is most
soluble at 60oC?
• 5) Which salt on
Table G shows the
least change in
solubility
between 30oC
and 70oC?
• 6) 108 g of KNO3
at 60oC
•
• 7) 20 g of NH4Cl
at 30oC
• 9) What is the
solubility of
NaNO3 in 100
grams of water at
40oC?
• 10) How many
grams of KClO3
can be dissolved
in 1000 g of water
at 30oC?
• 11) What is the
solubility of NaCl
in 50 grams of
water at 70oC?
• How many
grams of solute
must be added
to a solution
containing 30 g
of NH4Cl in 100
g of H2O at 90oC
in order to make
it a saturated
solution?
• A solution
contains 80 g of
KNO3 in 100 g of
H2O at 80oC. To
what
temperature
must the
solution be
lowered in order
to make it a
saturated
solution?
• Consider a
saturated
solution of
NaNO3 in 100 g
of H2O at 70oC.
If the solution is
cooled to 20oC,
how many
grams of solute
will precipitate?
• 15) How many
grams of solute
will precipitate if
a saturated
solution of
NaNO3 in 50. g
of water at 30oC
is evaporated to
dryness?
• 16) At what
temperature do
KCl and HCl have
the same
solubility?
Do Now
• TURN IN YOUR CSI LAB
• Take out your notes packets and reference
tables
• Open your notes to page 8/9
• Leave them open for now
• Notes check on this periods stuff before you
leave
Neighbor Practice
• Using R.T. G, answer the following regents
questions.
• Answers are on the back to check as you go
• Quiz on this stuff tomorrow
• After this, we are going to get into
concentrations, so make sure through page 9
is done in your notes
• HOMEWORK: Make sure to finish the lab,
READ AND DO PAGES 10, 11, 12!
Notes check time
• On solubility
• Can use your notes
Do Now
• TURN IN YOUR CSI LAB (only 7 people did)
• Take out your notes, opened to page 8-9
• Pick up a copy of the lab and read over the
background
Any Questions on The Homework
•
•
•
•
•
Molarity = moles/liter
Dilutions: M1V1= M2V2
Percents?
Ppm?
Quiz tomorrow on it…
TONIGHTS HOMEWORK
• READ AND DO PAGES 10, 11, 12!
• HONORS: Also read pages 14+15
• Lab due Monday
Safety:
• Bunsen burner safety
• Heating things up over the Bunsen burner, be
careful not to burn yourself
• ‘Snowing’ = record the temperature
– Not a couple of particles, but really looks like its snowing
• DO NOT EMPTY ANYTHING OUT BETWEEN TRIALS
– Just reheat it to dissolve it all again…
• Measuring out the correct mass is critical, do a good
job
Big idea
• We have an unknown salt
• We are going to create a solubility curve for it
• Each group will have a different amount of salt
to dissolve
• Collect data as a class
• Compare our graph to the R.T. and ID which it
best matches with
Assigned grams of
salt / 10.0 g of H2O
3.0 g
4.0 g
5.0 g
6.0 g
7.0 g
8.0 g
Average Crystallization
Temperature (oC)
(X-Axis on Graph)
Grams of salt
100 grams H2O
(Y-Axis on Graph)
Assigned grams of
salt / 10.0 g of H2O
3.0 g
4.0 g
5.0 g
6.0 g
7.0 g
8.0 g
Average Crystallization
Temperature (oC)
(X-Axis on Graph)
Grams of salt
100 grams H2O
(Y-Axis on Graph)
Notes Check Time
• Just on Solubility, you may use your notes
• ~9 minutes
Do now
• TURN IN YOUR Magical Mystery Salt LAB
• Take out your notes packet and open to pages
8+9
Concentration of solutions; How do
we measure how ‘concentrated’ a
solution is?
• Being able to quantify how concentrate a
solution is, is very important. There are a
number of different ways to measure this, and
each is easier to use in different situations.
a)
Molarity: Moles of solute / Liter of
solution
• As suggested by its name, molarity has to do
with how many moles are dissolved in a liter
of solution and the unit used to measure it is
called molar. For example, if you had a 1 molar
solution of NaCl (aq), you know you would
have one mole of NaCl for every liter of
solution. This way of measuring concentration
is the most common in the chemistry lab.
a)
Molarity: Moles of solute / Liter of
solution
• To experimentally determine the molarity of a
solution:
•
1) Determine the volume of solution you have
•
2) Determine how many moles of solute are
dissolved in the solution by
•
a) Evaporating off the solvent
•
b) Weighing the solute
•
c) Dividing the mass of the solute by the
formula mass of the solute
•
3) Molarity (M) = moles of solute/L of solution.
Molarity Simulator
• Show values, lets crunch some numbers!
• File
• internet
Practice:
• 1. What is the molarity of a solution if it contains
2.0 moles of KNO3 in 4.0 L of solution?
• 2. What is the molarity of a solution if it contains
2.0 moles of NaCl in 250. mL of solution?
• 3. What is the molarity of a solution if it contains
20. grams of NaOH in 2.0 L of solution?
Practice
• 4. How many moles of NaOH are needed to
make 4.0 L of a 0.50 M solution of NaOH?
•
4b. How many grams of NaOH would this
be?
• 5. How many grams of KCl are needed to make
500. mL of a 0.100 M solution of KCl?
i)
Making dilutions
• Making dilutions is a crucial skill for a chemist,
and is one that I as your teacher use often. For
example, the hydrochloric acid that we order
comes in a concentration of 6.0 molar, or 6.0
M. This is very concentrated and needs to be
diluted for what we do in lab.
i)
Making dilutions
• Before we get into the math, let’s think conceptually
about what is happening when we dilute something. I
pour out a little bit of the 6.0 M HCl into a beaker. As
long as I don’t spill any of this solution, the total
amount of HCl in that beaker shouldn’t change. If I add
more water to it, there is still the same number of
moles of HCl in the beaker, it just makes it less
concentrated. Therefore we know that the moles that
we start with (n1) has to be the moles that we end up
with (n2). To figure out the initial number of moles we
rearrange the molarity equation to solve for moles and
we get;
i)
Making dilutions
• Molarity1 x Liters1 = n1
• Molarity2 x Liters2 = n2
• Since the moles we start with has to equal the
moles we also get:
•
n1 = n2
• Now we can set the first two equations equal to
each other and we get
• Molarity1 x Liters1 =
Molarity2 x Liters2
OR M1 V1 = M2 V2
i)
Making dilutions
• Practice
• 1. You start with 1L of 6M HCl (aq) and dilute it to 6L.
What is the concentration of this new solution?
•
• 2. How much .1M NaCl (aq) solution can you make
from 100.mL of 2M NaCl (aq)?
•
•
• 3. How many milliliters of 6.0 M HCl (aq) are needed to
make 100.mL of .1M HCl (aq)?
c) Percent by volume: (volume
solute/volume solution) x 100
• Just like percent by mass, except you use the volumes
of solute and solution. This is used for liquid solutes,
like alcohol. The percentages of alcohol on alcoholic
beverages are given by volume. Generally speaking, if
something is 50% alcohol by volume it is flammable.
This is where the term proof comes from…back in the
old days, a bartender might water down the whiskey to
save money. Whiskey was supposed to be at least 50%
alcohol by volume. If a patron demanded proof that
the whiskey wasn’t watered down, a sample had to be
touched with a flame. If it wouldn’t burn, the
bartender might be shot! Or just run out of busines
Public Service Announcement: Do not
drink underage, or at all! Alcohol is a
poison
d) Parts per million: (mass of
solute/mass of solution) X 1 000 000
• This unit is similar to percentages. Percentages
give you the part out of 100, whereas ppm gives
you the parts out of 1,000,000. It is used to
determine trace amounts of dissolved ions in
drinking water. Established toxic threshold levels
are reported in ppm or sometimes ppb (parts per
billion) if it is a particularly nasty toxin. It is also
used to measure the concentration of
particulates in the air. Air pollution is measured
in parts per million, as is dust in a clean room at
an electronics manufacturing plant.
d) Parts per million: (mass of
solute/mass of solution) X 1 000 000
• What is the concentration, in ppm, of lead
ions in 100. g of tap water with 0.0000450 g of
lead ions dissolved in it?
• ppm = (g of solute / grams of solution) X 1 000
000
•
= {(0.0000450 g) / (100. g)] X 1 000 000
•
= 0.45 ppm
Concentration Practice
• 1) A sample of tap water is analyzed and
shown to contain 0.015 grams of lead ions per
10 grams of solution. Calculate the
concentration, in ppm, of this solution.
Concentration Practice
• 2) Lead is a heavy metal that is
found in car batteries. If they are
disposed of in the dump, they can
leach the lead out and
contaminate the ground water.
The EPA has been called in to test
the water around one particular
dump and found that every 1000.
g of groundwater tested contains
0.00027 grams of lead. The EPA’s
legal limit on lead concentration is
0.015 ppm. Does the dump site
break the legal limit? Show your
work.
Concentration Practice
• 3) Calculate the percent by mass of a solution
that contains 35.8 grams of Na2SO4 in 136.3
grams of solution.
Concentration Practice
• 4) Calculate the percent by volume of a
solution that contains 4.55 mL of ethylene
glycol in 7.83 mL of solution.
Do Now
• Pick up a copy of the notes check and get
started
• treat it like a quiz (done individually)
• You will have 10 minutes from the bell
• Bonus: Which of the following 1 molal
solutions will have the LOWEST BOILING
POINT:
– NaCl
C6H12O6
K3PO4
Cu(NO3)2
4) Conductivity; Electrolytes vs.
nonelectrolytes
• Electrolytes: Most ionic compounds and many acids dissolve well in water.
These are called electrolytes, because they cause the solution to conduct
electricity due to the free-moving ions. They ionize 100% in water to yield
ions in a reaction that resembles a decomposition reaction. The reaction is
called dissociation, and it is a physical change, not a chemical change. The
more ions a solute breaks up into, the more conductive it can become (as
well as the higher the boiling point and the lower the freezing point of the
solution will be).
• NaCl (s)  Na+1 (aq) + Cl-1 (aq)
• One mole of sodium chloride dissolves to form one mole of sodium ions
and one mole of chloride ions (2 moles of dissolved ions total).
• CaBr2 (s)  Ca+2 (aq) + 2 Br-1 (aq)
• One mole of calcium bromide dissolves to form one mole of calcium ions
and two moles of bromide ions (3 moles of dissolved ions total)
See how they break up
• http://phet.colorado.edu/en/simulation/solub
le-salts
• File
• Conductivityfile
• http://phet.colorado.edu/en/simulation/sugar
-and-salt-solutions
My conductivity tester
Practice:
Ionic Compound
KHCO3
Fe(C2H3O2)2
Mg(OH)2
CaBr2
# of and identity of CATION # of and identity of ANION Total # of Ions
Nonelectrolytes:
• Substances formed from covalent bonding (nonmetals
bonded together) do not dissolve into ions upon entering
the water. These include polar molecules that dissolve, but
do not ionize. These include sugar (C6H12O6, C12H22O11),
antifreeze (CH2OHCH2OH ) and alcohol (C2H5OH). These
have less impact on the melting and boiling point of a
solution than ionic compounds do, because they do not
break up any further.
• C12H22O11 (s)  C12H22O11 (aq)
• One mole of sucrose dissolves to form one mole of
dissolved sucrose. No ions are formed, so no electricity can
be conducted.
Colligative properties: What happens
to the properties of the solution when
stuff is dissolved?
• - COLLIGATIVE PROPERTIES OF SOLUTIONS are
physical properties of solutions that depend on
the concentration of solute in a given amount of
solvent.
• a)Freezing Point Depression: The freezing point
of water decreases as solute is added to it.
• b) Boiling Point Elevation: The boiling point of
water increases as solute is added to it.
Anitfreeze
•
•
•
•
•
Antifreeze. It isn’t just for breakfast anymore. Actually, it never was, as it is a deadly poison. As it metabolizes, it forms
razor-sharp crystals in the kidneys, liquefying them and leading to an excruciatingly painful death. Keep it away from
children and pets. There is an antidote that prevents the crystals from forming, but it has to be administered before it
metabolizes to that point.
It might not be good to drink, but it is excellent at preventing the water coolant in your car’s engine from boiling or
freezing. In hot weather, going up a steep hill, your car’s engine produces a lot of heat. Water flowing through pipes in
the engine carries heat out of the engine, where it passes through the radiator and cooled before being sent back to the
engine. The temperature might reach 100oC, the boiling point of water. If the water is allowed to boil, the pressure of
the steam that is produced might cause the engine to crack. In addition, steam is only half as efficient per gram as liquid
water at carrying heat away from the engine.
This water coolant is still in your engine when the weather is cold. If the car is parked outside in sub-freezing
temperatures, the water in the engine’s coolant pipes might freeze. Water expands when it freezes, and this would cause
the pipes to burst, causing expensive repairs and towing costs.
Adding a solute like antifreeze helps tremendously, because the solute makes it a lot harder for the water to boil or
freeze. Remember, when solutes dissolve, water molecules hold on to the solute particles to keep them apart. To boil,
the water has to be detached from the solute particles, which requires adding more energy than usual. When dissolving
solutes in water, the boiling point increases. The more solute that is dissolved, the higher the boiling point will go.
When a liquid like water freezes, it does so by forming a crystal lattice. The solute particles interfere with this process,
meaning that the solution has to be cooled down to a lower temperature than the normal freezing point for it to freeze.
The more solute that is added, the lower the freezing point will drop. This is why salt is dumped on the roadways during
the winter! The road has snow packed on it. A truck comes along and dumps salt on the snow. When cars drive over the
salted snow, the pressure and friction from the tires causes the snow to melt. The salt dissolves in the freshly melted
snow, and prevents it from refreezing. The salt that is the least expensive to use is crushed halite salt (NaCl). More and
more communities are using a different salt, calcium chloride (CaCl2). This forms round pellets; you may have seen them
on the road or on a walkway. CaCl2 is more effective than halite salt at preventing the water from refreezing. NaCl
breaks up into two ions (Na+1 and Cl-1) when dissolved. Calcium chloride breaks up into THREE ions when dissolved (one
Ca+2 ion and two Cl-1 ions). The more ions that are dissolved in the water, the more they will interfere with water
freezing, and the freezing point of water will drop even further…or the less salt you will need! The more ions that form,
the greater the impact it will have on the melting and boiling points! Also, the more solute dissolved in solution, the
greater the impact on the melting and boiling points.
Antifreeze
• Without antifreeze:
water would boil from
the engine and
pressure would build
until it broke
• Water would freeze in
the winter and break
the pipes and such (ice
expands)
Antifreeze
• Dissolve stuff:
• boiling point increases
(now the water wont
boil)
• Freezing point goes
down: it has to get
REALLY cold for it to
freeze
Salt on the roads
• Dissolving salts  lower
freezing point
• If the ice is at -2oC and you
drop its freezing point by
adding salt to -6oC, its going
to melt!
Questions
• 1. Does adding salt to a pot of water really
make it boil faster? Explain.
• (actually, you would need about 240 grams,
over half a pound, of NaCl in 4 qts of water to
make it boil 2 degrees higher)
Compound Ionic Or
Molecular?
BaBr2
LiF
C2H6O
Fe(NO3)3
Electrolyte or How many
Nonelectrolyte? particles the
compound
breaks up into
Rank in order of which
one affects the boiling
and freezing points the
least to most
1 = affects them least
4 = affects them most
• ______1) Which of the following 1 molal aqueous solutions will have the
highest boiling point?
• a) NaCl (aq)
b) C6H12O6
c) K3PO4
d) Cu(NO3)2
•
• ______2) Which of the following 1 molal aqueous solutions will have the
lowest boiling point?
• a) NaCl (aq)
b) C6H12O6
c) K3PO4
d) Cu(NO3)2
•
• ______3) Which of the following 1 molal aqueous solutions will have the
highest freezing point?
• a) NaCl (aq)
b) C6H12O6
c) K3PO4
d) Cu(NO3)2
•
•
• ______4) Which of the following 1 molal aqueous solutions will have the
lowest freezing point?
• a) NaCl (aq)
b) C6H12O6
c) K3PO4
d) Cu(NO3)2
• ______5) Which of the following aqueous solutions will have the highest boiling
point?
• a) 500 g solute in 1000 g solvent
b) 500 g solute in 500 g solvent
• c) 1000 g solute in 500 g solvent
d) 1000 g solute in 1000 g solvent
•
• ______6) Which of the following aqueous solutions will have the lowest boiling
point?
• a) 500 g solute in 1000 g solvent
b) 500 g solute in 500 g solvent
• c) 1000 g solute in 500 g solvent
d) 1000 g solute in 1000 g solvent
•
• ______7) Which of the following aqueous solutions will have the highest
freezing point?
• a) 500 g solute in 1000 g solvent
b) 500 g solute in 500 g solvent
• c) 1000 g solute in 500 g solvent
d) 1000 g solute in 1000 g solvent
•
• ______8) Which of the following aqueous solutions will have the lowest freezing
point?
• a) 500 g solute in 1000 g solvent
b) 500 g solute in 500 g solvent
• c) 1000 g solute in 500 g solvent
d) 1000 g solute in 1000 g solvent
• D) Based on this chart, to the
right:
• 1) If your cooling system has a
capacity of 14 quarts, how many
quarts of antifreeze will be
needed to protect your car’s
engine down to -28oF?
• 2) Based on the bottom chart,
does dissolving a solute in water
provide a greater protection
against freezing or against
boiling? Explain, using the
information on the chart.
Determine the freezing and boiling
points of solutions
• A) Freezing Point Depression: For every mole of
particles that is dissolved in 1 kg of water, the freezing
point decreases by 1.86oC. Ionic compounds (made of a
metal and nonmetal or polyatomic ion) will break up to
form 2 or more ions in water. For example, a 1 m
solution of NaCl will have a 2 m concentration of
particles (because it breaks into 2 ions). A 1 m solution
of CaCl2 would have a 3m concentration of particles
because of the 1 Ca+2 and the 2 Cl- ions. Molecules
(made of covalently bonded nonmetal atoms,
remember?) do not break up into ions when dissolved.
2 m antifreeze (ethylene glycol) contains 2 m of
dissolved particles.
Determine the freezing and boiling
points of solutions
• Tf = Kfm
• Tf = freezing point depression,
• Kf = freezing point depression constant
(1.86oC/m for water)
• m is the molality (moles solute/kg solvent) of
the dissolved particles, taking into account
electrolytes.
• Ex. What is the freezing point of a 2.0 m solution of
CaCl2 (aq)?
• CaCl2 is ionic, so it ionizes to form three ions (1 Ca+2
and 2 Cl-1).
• 2.0 m of solution has 2.0 X 3 = 6.0 m of dissolved
particles.
• Tf = Kfm = (1.86oC/m) X (6.0 m) = 11 oC
• Since water freezes at 0oC, the new freezing point
will be depressed by 11oC:
• 0oC – 11oC = -11oC
• Ex. What is the freezing point of a 3.0 m solution of
C12H22O11 (aq)?
• C12H22O11 is made entirely of nonmetals, so it is a
nonelectrolyte.
• 3.0 m of solution has 3.0 m of dissolved particles.
• Tf = Kfm = (1.86oC/m) X (3.0 m) = 5.6 oC
• Since water freezes at 0oC, the new freezing point
will be depressed by 5.6oC:
• 0oC – 5.6oC = -5.6oC
B) Boiling Point Elevation:
• For every mole of particles that is dissolved in
1 kg of water, the boiling point increases by
0.52oC.
• Tb = Kb m
• Tb = boiling point depression,
• Kb = boiling point depression constant (0.52oC
for water)
• m is the molality of the dissolved particles,
taking into account electrolytes.
• Ex. What is the boiling point of a 2.5 m solution of
NaCl (aq)?
• NaCl is ionic, so it ionizes to form two ions (1 Na+1
and 1 Cl-1).
• 2.5 m of solution has 2.5 X 2 = 5.0 m of dissolved
particles.
• Tb = Kbm = (0.52oC/m) X (5.0 m) = 2.6oC
• Since water boils at 100oC, the new boiling point
will be elevated by 2.6oC:
• 100oC + 2.6oC = 102.6oC
• Ex. What is the boiling point of a 1.5 m solution of
CH2OHCH2OH (aq)?
• CH2OHCH2OH is made entirely of nonmetals, so it is
a nonelectrolyte.
• 1.5 m of solution has 1.5 m of dissolved particles.
• Tb = Kbm = (0.52oC/m) X (1.5 m) = 0.78oC
• Since water boils at 100oC, the new boiling point
will be elevated by 0.78oC:
• 100oC + 0.78oC = 100.78oC
• E) Calculate the phase change points of the following
solutions:
•
• 1) Freezing point of 0.500 m C6H12O6
•
• 2) Boiling point of 3.00 m KCl
•
• 3) Freezing point of 2.00 m Na2CO3
•
• 4) Boiling point of 0.100 m Al(NO3)3
•
• 5) Freezing point of 1.50 m C2H6O2
Do Now
• Turn in Your Magical Mystery Salt Labs
• Pick up a copy of the next units work packet
• Take out your notes pack and open to the
review
Solutions Review
• 1) What is a solution?
•
•
•
• 2) How does a solution form?
•
•
•
• 3) What is solubility?
• 4) Fill in the chart below with either
increases, decreases, or remains the same for
changing the following factors on the
SOLUBILITY of the solute in water:
Solute
CO2 (g)
NaCl (s)
Increasing Decreasing Increasing
Temperature Temperature Pressure
Decreasing
Pressure
5) Using Reference Table G, determine
the solubility of:
o
a) NaNO3 in 100 g of water at 30 C
o
b) NaNO3 in 200 g of water at 30 C
o
c) KNO3 in 100 g of water at 40 C
o
d) KNO3 in 50 g of water at 40 C
• 6) Using Reference Table G, determine if the
following solutions are saturated, unsaturated or
supersaturated. If they are anything but saturated,
list two things you can do to make them saturated
(include numbers).
Solution (in 100g
H2O)
40 g of KClO3 at 50oC
110 g NaNO3 at 45oC
70 g KNO3 at 60oC
70 g NH4Cl at 70oC
Sat, Unsat, Supersat +/- how many oC to
make saturated?
+/- how many g to
make saturated?
7) Calculate the molarities of the
following solutions:
• a) 120 g NaOH in 500. mL of solution
•
•
• b) 3.0 moles NaCl in 750. mL of solution
•
•
• c) 50.0 g of NaNO3 in 2.5 L of solution
8) Calculate the number of grams of
solute needed to make the following
solutions:
• a) 2.00 L of 0.50 M NaBr (aq)
•
•
• b) 250. mL of 3.0 M KNO3 (aq)
•
•
• c) 350. mL of 0.10 M HCl
9) Calculate the following
concentrations:
• a) In ppm, of 0.044 grams of mercury ions in 200.
g of solution
• b) In % by mass, 3.88 grams of NaCl in 10.0 g of
solution
• c) In % by volume, 5.63 mL of ethyl acetate in
7.89 mL of solution
10) HONORS Calculate the melting
point and freezing points of the
following solutions:
Molality of solution:
1.5 m C6H12O6
2.7 m NaCl
3.3 m CaCl2
8 m C2H6O2
Freezing point
Boiling Point
Okay, lets look at concentrations
again…
• What is the ppm of HCl if a solution has 365
grams of HCl dissolved in 3 kg of solution?
Okay, lets look at concentrations
again…
• What is the percent of HCl if a solution has
365 grams of HCl dissolved in 3 kg of solution?
What is the molarity of a solution that
has 365 grams of HCl dissolved in 4
liters of solution?
How much 1.0 M HCl solution can you
make from that?
Any Questions?
P1+7
P3
Topic
Homework (Due at the beginning of
the next period)
2/5
2/5
Acids, Bases and their properties
Read next topic; 2)Indicators + 3)pH.
Do the practice
2/6
2/6
Indicators and pH
Read next topic 4)Acid and Base
Neutralization, Do the practice
2/8
2/7
Acids, bases and indicators lab
2/8
2/7
Acids, bases and indicators lab
2/6
2/8
Acid-Base Neutralization
Finish the lab (due 2 days later)
Read the next topic; 5) Bronstedlowry
Do the practice
2/7
2/12
Titration practice
2/12
2/11
Titration lab
2/12
2/11
Titration lab
Finish the lab (due 2 days later)
2/11
2/13
Bronsted-Lowry Acids and bases
Do the review problems and study
for the test
2/13
2/14
2/13
2/14
Review
Study for the test
Test