Non-Dairy Creamer and Surface Area - (Brent Shano)
Author
Brent Shano
Principles Illustrated
Surface area is increased as the particles used for combustion get smaller.
There is an inverse relationship between surface area and rate of combustion
Combustion Reactions in general : HydroCarbon + O2 => CO2 + H2O
Standards
HS-PS1-5 Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.
HS-PS3-3 Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy
Questioning Script
Prior knowledge & experience:
Students know they need to chew their food so they don't get a stomach ache. Big pieces take longer and are harder to digest. Student's know that when you put granulated sugar in beverage like tea over a sugar cube that it dissolves faster.
These concepts of surface area leading to increased absorption are one thing, but using the same concept to illustrate combustion can leave them a little confused. Now bond energy becomes a factor and words like exothermic and endothermic reactions need to be understood in addition to surface area. All these things come together and now combustion becomes the hot topic. Pun intended.
(If you, as the teacher, wanted to you can also give previous knowledge on grain silos catching fire as a segue to the event.)
Root question:
What will happen to the piece of wood block when put in the fire?
(most students think it will ignite quickly and burn)
Target response:
The piece of wood block due to its small surface area will not ignite as fast at students think. Eventually if you were to leave the block of wood in the fire (Bunsen Burner) in the same spot it will ignite and burn. I purposely move the block of wood in and out the flame to prevent this from happening. However, the particulates of the nondairy creamer do not have this luxury.
The increased surface area of the nondairy creamer allows for a very quick ignition to take place and ensures a guaranteed and rather "sugary smelling" combustion reaction.
Common Misconceptions:
Most students think that the block piece of wood will ignite quickly and burn. Plus most students do not know that nondairy creamer is a sugar. As such it is a carbohydrate, and reacts like a hydrocarbon when mixed with oxygen to perform a combustion reaction. The reaction that takes place really shocks them. They enjoy it especially once they learn the science behind it, I find they appreciate the process just that much more.
Photographs
