Chemical Demonstrations

1
Chemical Demonstrations

• ETnMSP - 2008
• Terry Bunde
• Maryville College

2
Methanol Cannon

• Ten milliliters of methanol is added to a one
  liter polyethylene bottle with a piezo igniter.
  The bottle is shaken to fill the bottle with
  methanol vapor and the excess methanol is drained
• A rubber stopper is fitted to the top of the
  bottle and the igniter sets off a methanol-air
  explosion sending the cork into the air

3
Construction of a Methanol Cannon
4
Whoosh Bottle

• Twenty milliliters of methanol is added to a 5
  gallon polyethylene carboy and the carboy is
  shaken to fill the bottle with methanol-air vapor
  mixture. A lighted stick is brought to the top
  of the bottle and the methanol fumes are ignited.
  The burning methanol flashes back into the
  bottle and causes a whooshing sound, the pitch is
  determined by the diameter of the bottle neck.
  This demonstration is very impressive if a clear
  plastic (PETE) bottle is used in a darkened room

5
Whoosh Bottle
6
Burning Gummy Bear

• A test tube with a small amount of potassium
  chlorate (KClO3) is slowly heated with a burner
  until the salt melts
• A Gummy Bear is added to the test tube and a
  violent reaction starts as the sucrose reacts
  with the potassium perchlorate to form carbon
  dioxide and water vapor. The chlorate salt
  serves as a source of oxygen gas to fuel the
  combustion which is a highly exothermic process.

7
Reaction

• 2KClO3 heat ? 3 O2 2 KCl
• C12H22O11 12 O2 ? 12 CO2 11 H2O
• As the tube cools the potassium chloride
  remaining after the reaction solidifies as a
  white salt.

8
Gummy Bear Combustion
KClO3
9
Elephants Tooth Paste

• About twenty milliliters of 30 hydrogen peroxide
  is added to a 1000 mL glass graduated cylinder
  along with several milliliters of liquid dish
  washing detergent.
• Red and Green food coloring is dripped along the
  walls of the cylinder and a few grams of
  potassium iodide is dumped into the cylinder as a
  tube of colored foam erupts from the cylinder
• The foam is VERY hot and extreme care should be
  taken to avoid contact while conducting the
  demonstration

10
Reaction

• 2 H2O2 ? 2 H2O O2
• H2O2(aq) I-(aq) ? OI- (aq) H2O(l)
• H2O2(aq) OI-(aq) ? H2O(l) O2(g) I-(aq)
• The oxygen is produced in a violent reaction and
  trapped in the detergent foam which erupts from
  the cylinder along with steam. A glowing splint
  pushed into the foam clearly shows that the foam
  contains oxygen gas as the splint reignites and
  burns

11
Elephants Toothpaste
12
Exploding Egg

• A large bird egg (ostrich or emu) has two holes
  placed in the long ends and contents of the egg
  removed
• The egg is dried in air and a small piece of
  sticky tape is placed over the top hole in the
  narrow end of the egg
• Hydrogen produced from the reaction of mossy zinc
  and hydrochloric acid is allowed to flow through
  a narrow plastic tube into the bottom of the egg,
  displacing the air with hydrogen
• The tape is removed and the hydrogen ignited with
  a candle taped to a meter stick

13
Exploding Egg Explained

• As the hydrogen burns from the top of the egg,
  air is pulled into the egg through the bottom
  hole
• When the air entering reaches a critical
  explosive mixture of air and hydrogen, the flame
  flashes back into the egg causing it to explode
  into many small pieces or even dust with a very
  loud retort (you may want to have people plug
  their ears to avoid any temporary hearing loss)

14
Burning Towel

• A cotton dish towel is soaked in 70 rubbing
  alcohol (isopropanol) and placed over a ring
  attached to a ring stand.
• The alcohol is ignited and flames will clearly be
  seen coming from the towel, but the cotton is not
  consumed
• The water left over after the alcohol is
  combusted in air prevents the towel from burning

15
Burning Steel Wool

• Very fine steel wool is first cleaned in hexane
  to remove any oil applied to prevent rust. The
  steel wool is removed and allowed to dry in air
• A small steel wool sample is fluffed up and hung
  from a ring on a stand and a flame is brought
  near the edge (in an alternate approach, a 9 volt
  battery can be touched to the steel to start a
  fire)
• The steel burns in air (especially if air is
  directed right at the burning surface)

16
Composition of AirPercentage of Oxygen

• Cleaned steel wool can be pushed into the bottom
  of a clean test tube
• The tube is inverted in a water bath and the
  steel fibers allowed to rust over several days.
• The volume of the air in the two is reduced
  causing the water to rise in the tube, the volume
  is approximately 20 of the volume of air
  indicating the percentage of oxygen in air
• This demonstration can be extended to fill tubes
  with nitrogen, hydrogen, helium and have students
  predict what will happen. Oil can be applied
  (WD40) to the steel wool before it is placed in
  the test tube and the results observed.

17
Composition of AirPercentage of Oxygen

• The chemistry of the oxidation of steel is very
  interesting. The product is ferric oxide (Fe2O3)
  and the mass of the combustion product is greater
  than the steel wool sample that you started with
• The oxidized steel wool can be massed before and
  after oxidation and the stoichiometry of the
  reaction determined

18
pH Indicators in Nature

• Purple cabbage can be extracted in 70 isopropyl
  alcohol by placing leaves in the alcohol and
  heating them in a microwave. This solution can
  be stored for several months without any
  bacterial degradation
• A series of common household products is placed
  in the wells of a white egg carton and the colors
  noted.

19
Common Products Used
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)