Let’s talk for a moment about reaction rates. There are several ways to increase the rate of reaction – increasing temperature, agitation, and increasing surface area. In regards to this last point, specifically I mean the surface area to volume ratio.
Think about it this way: surface area refers to the stuff on the outside – that’s the part of the substance that can react. But volume refers to all the matter, including the stuff inside that’s still waiting to react. So a large block of ice will melt much slower than crushed ice. On the chemical reaction side, try this experiment:
What to Do:
- Place a whole effervescent tablet (like Alka-Seltzer®) into an empty cup.
- Crush up a second effervescent tablet. I suggest putting it into a folded piece of paper and using a rubber mallet – it makes it much easier to crush and to pour out the crushed matter.
- Pour the crushed material into a second cup
- Pour an equal amount of water into each and watch what happens
A whole effervescent tablet has a relatively low surface area to volume ration with a great deal of the tablet waiting to react on the inside. But, the higher ratio crushed tablet has exposed a great deal more of the inside to the outside, thereby allowing more of it to react simultaneously.
This same idea is one of the core strengths of nanotechnology. Remember that nanotechnology involves the manipulation of materials at the nanoscale to take advantage of these unusual properties, with the nanoscale involving materials around a billionth of meter. For perspective, your DNA is about 2.5 nanometers (nm) wide and your fingernails grow at the rate of about 1nm per second. Yeah, its really, really, really, really small.
But, being really, really, etc. small has benefits in regards to reaction rate, as they have a VERY high surface area to volume ratio. So, the entire substance can react at a much faster pace. If you want to learn more about nanotechnology, make sure to stop by the Super Small Matter Lab in Matter Factory at the Children’s Museum of Houston or visit http://www.nisenet.org/public.
By the way, thanks to my friends at OMSI and the NISE Network for the experiment that inspired this video!