Light absorption Explosions Corrosion Geological Energy Barrier in Reactions AUMSP Module Chemical and physical reactions have energy barriers or an activation energy E a that must be overcome to permit reaction ID: 913679
Download Presentation The PPT/PDF document "Kinetic Time Scales AU-MSP Module" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Kinetic Time Scales
AU-MSP Module
Light absorption
Explosions
Corrosion
Geological
Slide2Energy Barrier in Reactions
AU-MSP Module
Chemical and physical reactions have energy barriers, or an activation energy (
Ea), that must be overcome to permit reactionUnassisted reaction
Diet Coke bottle left open for several daysCatalysts act to lower this energy barrier and enhance speed
Mentos (and other additives) can be considered catalysts for the physical reaction in which dissolved CO2 changes to gaseous CO2Catalyzed reaction much faster than unassisted reaction (control)
Slide3Mentos as a Catalyst
AU-MSP Module
http://www.stevespanglerscience.com/experiment/original-mentos-diet-coke-geyser
Slide4Mentos as a Catalyst
Contributing factors
Rough surfacesPromotes nucleation, or formation, of CO2 bubbles from dissolved CO2Rapid descent of “catalyst” particlesLow friction from surfactants and shapeRelatively heavyRapid reaction in large bottles
AU-MSP Module
Coffey, T. S.,
Am
. J. Phys. 2008, 76, 551.
Scanning
Electron Microscope (SEM) image of Mentos candy surface
Scale
bar is 20
μ
m long
(20 millionths of a meter)
Slide5Table Salt as a Catalyst
AU-MSP Module
SEM
images of table salt Scale bars are (a) 2.0 mm; (b) 100 µm; (c) 50 µm; and (d) 20 μm long
Contributing factorsRough surfacesSlower descent into bottleSmaller particlesSlower reaction in larger bottle
High surface area-to-volume ratioAlong with surface roughness, promotes rapid reaction in smaller scale systems (indoor experiments)
Coffey, T. S., Am. J. Phys. 2008, 76
,
551.