Torricelli

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Torricelli
Laws of motion Thermometer Telescope Compass
Galileo

• Torricelli served as Galileo's secretary from
  1641 to 1642

Galileo died 8 Jan 1642
Barometer was invented in 1643
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Check homework

• Make sure that you can
• Answer the questions
• Do all the word problems
• Do the word problems on handout 40
• Ideal gas law handout
• Handout 28

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Return papers
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When you first place a molecule in a solution
then if the solution can be dissolved it will go
into solution
unsaturated
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At equilibrium there are as many red molecules
going into solution as there is red molecules
going out of solution
saturated
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At equilibrium the amount of solute going into
solution equals the amount of solute going out of
solution

• Solubility
• equilibrium

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If you cool a substance down or if some of the
solvent evaporates off then a molecule must come
out of solution then it is considered
temporally supersaturated until equilibrium is
again reached
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• Is carbon tetrachloride, CCl4, soluble in water?
• Is dimethyl ether, CH3OCH3, soluble in water?
• Is ethanol, CH3CH2OH, soluble in water?
• Is propane, CH3CH2CH3, soluble in water?
• 
  

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• Keeping in mind that "Like Dissolves Like", which
  of the following compounds would be
• the most soluble in a nonpolar solvent such as
  carbon tetrachloride, CCl4?
• A) H2O
• B) CH3OH
• C) CH3CH2CH2CH2CH2OH
• D) CH3CH2CH2OH

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NaCl 35.7g NaCl in 100 g H2O at 0OC

• NaOH 42.0 g in 100 g H2O at 0OC
• FeCl3 74.4g in 100 g H2O at 0OC
• MgSO 22.0 g in 100 g H2O at 0OC
• C6H12O6 179.2g in 100 g H2O at 0OC

Degree of Solubility g per 100g H2O at a given
temp
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What factors affect how soluble something is

• How hot the solvent is
• Polarity, How easy a block of substance is
  broken by the solvent or goes into solution
• The surface area of the solute

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Solubility curve
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Solubility of sugar in water
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Saturate room temperature water with sugar
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So as the heat goes up then more solute can be
carried by the solvent
Super saturate the solvent (water) with solute
(sugar)

• On the other hand the less heat the less ability
  the solvent has to carry the solute

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As the sugar water solution cools down, what
happens to the sugar?

• The solvent can no longer hold the solute and the
  solute falls out of solution and globs

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So Hot liquids hold more soluteHot liquids hold
less gas

• Rock candy

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• Unsaturated
• Supersaturated
• saturated

Identify the areas that are unsaturatedsupersatu
ratedsaturated
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Who has ever used HEAT product in their gas to
keep water out

• Gasoline freezes at 70 Fahrenheit

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Gases have strange solubility properties Gases
dont glob

• Gases are free moving unencumbered molecules
• Gases do not become assimilated by the solvent
  but move into the spaces between solvent molecule
  because there is room and they happen to be
  floating by

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Gasesare notassimilatedby the solvent
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A solvent is saturated by a gas when the number
of gas molecules floating in equals the number of
gas molecules floating out

• Kind of like kids moving in and out of a store in
  the mall

Equilibrium
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You can force more gas into a solvent with
pressurePressure is adding more atoms by adding
more atoms to the surface of a solution

• Take the pressure off and the gas will leave the
  solution

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Henrys Law

• the solubility of a gas increases as
• the partial pressure of the gas on the surface of
  the liquid increases.

The more atoms or molecules of a gas striking the
surface of a liquid the more gas will go into
solution
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Pressure of the gas over the liquid
Higher pressure greater concentration of gas on
surface so greater number of gas molecules
entering water
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Which do you think holds more gas, Hot water or
cold water?

• Hot Water molecules heat the gaseous molecules
  causing them to move very rapidly and move far
  apart. Therefore less gas molecules will fit in
  the water.
• Cold Water allows the gas already in the water
  to move slowly and stay more condensed in
  solution in greater amounts.

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When you see dead fish on a small lake is it
because the fish got too hot?
Not enough oxygen dissolved in the water
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When you see dead fish on a small lake is it
because the fish got too hot?
Not enough oxygen dissolved in the water
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• Which will explode with more fervor, opening a
  warm coke or a cold coke, Why?

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An electrolyte is a substance that dissolves in a
liquid solvent and provides ions that conduct
electricity.
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In order for an electrolyte to carry an electric
current there must be available charges for the
electron to jump to
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Electrolytes are considered as

• Strong electrolytes completely dissociate into
  ions and conduct electricity well.
• Weak electrolytes provide few ions in solution.

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When we did the electrolysis of water we had to
put acid in the water so the water would carry a
current
How does acid cause water to ionize?
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An acid is an unstable molecule that shoots a
hydrogen atom without an electron loose

• These protons (H) stick to any negative pole
  that is around and create positive ions

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H2O H ? H3O hydronium

• It is hydronium that allows water to carry a
  current.
• Water can also carry a current if NaCl is added
  to the water. Na is the part that can carry a
  current, not Cl-

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But how does the presence of a solute effect the
properties of the solvent.

• Colligative Properties

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We all know that when it gets very cold outside
we put salt on the roads to interfere with the
freezing of water.

• WHY????????

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Normally water freezes at O degrees

• If we add salt to the water the Na and the Cl-
  interfere with the hydrogen bonding of the water
  molecules and prevents the crystallization of
  water.
• Thus salt water freezes not at O degrees but
• 20 degrees C (-4 F).

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Pile of tires and box story
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But is there something especially magical about
salt. What is so special about salt.

• Will
• sugar
• KBr
• MgCl2
• Oil

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Sugar, calcium chloride, almost any polar
substance that would interfere with the
electrostatic attraction of the hydrogen bonds of
the water will decrease the freezing temperature.

• The extent that a polar compound changes the
  freezing point is called the
• Freezing point depression

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Do you think NaCl influences the freezing point
depression to the same degree as MgCl2?
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The addition of a polar substance into water not
only decreases the freezing temperature, it also
changes the boiling point 
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Water boils by individual H2O molecules breaking
loose from the hydrogen bonds of liquid water

• The presence of a solute in the water acts as a
  barrier to the gas from escaping form the water.

Kind of like placing a turnstile in front of the
entrance into a auditorium
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In this monument it would be easy for a group of
people to enter or leave from the building
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If however a red turnstile is placed in the
doorways then the flow of people will be
disrupted and more energy will be needed for the
people to exit
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The solute interferes with the escape of gaseous
water so you need to add more heat to achieve
boiling temperature
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The change that a solute in a solution makes to
the boiling point is called the Boiling point
elevation

• Stack of tires and a few pesky boxes
• Trying to get out of the water when there are
  float toys in the water

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My moms spaghetti

• What examples can you think of
• other than salt
• that is an example of Colligative properties
  where there is freezing point depression and and
  boiling point elevation?

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Antifreeze

• Ethylene glycol

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what do they say about pets and ethylene glycol
sugar
Anti-freeze
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Do you think all substances lower the freezing
point and raise the boiling point the same
amount???? 

• No

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Aqueous means in water
Boiling and Freezing point changes for some
aqueous solutions
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It is the number of particles or ions or
molecules that influence the colligalitive
properties.

• The mass of the particles is not a factor

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There is an equation that allows us to calculate
the temp change

• ?Tb kb x m Kb 0.51 for H2O
• ?Tf kf x m Kf -1.86 for H2O

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Review for the exam