Facilitating Communication about Measurement, Exponents, and Scientific Notation 
Part 1
Second video on page
		
Video TranscriptStudent 1: "The question was: a single atom of carbon
weighs approximately 1.99*10-23 grams and about
how many atoms are there in a kilogram of carbon?"Student 2: "What we knew to start to figure out our
column: You said that one single atom weighs
2*10-23 grams and we said that 1000 grams equals
one kilogram."Student 3: "And we took the problem by doing a 1000
divided by 2*10-23 equals 1*103 divided by
2*10-23, which equals .5*1026."Teacher: "So you are comfortable with the fact
where she got the thousand?  Ok, yes?"Student 4: "I was wondering where she got the five
from?"Student 3: "The five is: 1 divided by 2 would equal
0.5."
http://illuminations.nctm.org/reflections/912/Facilitating_Communication/part1.html