Transcript Collapsing Can

Elephants’ Toothpaste
A tower of foam emerges from a graduated cylinder
Purpose
 To observe the rapid
decomposition of hydrogen
peroxide when treated with a
catalyst
Demonstration
 The hydrogen peroxide had a fewbubble
drops of detergent in it
 When potassium iodide KI was bubble
bubble
added it catalyzed the
decomposition of the hydrogen
peroxide
2H2O2
2H2O
+ O2
 The oxygen gas bubbled causing
the detergent to foam
Concepts
1.
Decomposition Reactions
2.
Peroxides
3.
Gases
1. Decomposition Reactions
 Any reaction of the general form
 AB
A
+
B
 In a decomposition reaction a single
substance breaks into two or more
substances
 We say the original substance has
“decomposed” which means it has
broken apart
2. Peroxides
 A compound which has an oxygenoxygen bond
 Hydrogen peroxide is a common
peroxide
 Chemical formula H2O2
 Chemical structure
H
O
O
H
3. Gases
 Occupy much greater volume than
the solid or liquid substances from
which they are formed
 Expand to fill or escape the
container they are in
 Will foam in the presence of a
detergent as in this demonstration
Conclusions
 Hydrogen peroxide decomposed to
form oxygen gas and water when
treated with a catalyst
 When trapped in detergent, the
oxygen gas bubbles expanded and
a foaming tower was produced
Comments
 Many different peroxides are
known to exist
 Benzoyl peroxide is a peroxide
used in acne medication which
released oxygen to kill facial
bacteria