Here is the link to a Bellingham teacher’s website who has posted Properties of Matter student sheets and reading questions in a PDF format.
http://wwwfms.bham.wednet.edu/Staff/boriss/propertiesOfMatterPart1.htm
Here is the link to a Bellingham teacher’s website who has posted Properties of Matter student sheets and reading questions in a PDF format.
http://wwwfms.bham.wednet.edu/Staff/boriss/propertiesOfMatterPart1.htm
Several SPS science teachers collaborated in 2005-2006 to align the chemistry content students learned in Middle School and High School. As a result, this working document was created describing lessons from the Properties of Matter module that could be changed, skipped, altered, augmented, etc.
How much red dye is left in each cup when you dilute the 10% solution seven times, each by a factor of 10?
One misconception that students can develop from this lab is that there is no red dye left in the cups where it can’t be seen. They calculate the concentration of red dye in each cup, and see on the EPA charts that even a 1PPM concentration can be harmful to organisms’ health depending on the chemical.
So how many molecules of FD&C Red #40 are in each cup? To find out, I started with the assumption that 10 drops of food coloring is 1mL and has a mass of 1g. You can adjust the following data by whatever % necessary to correct for any error in this assumption.
Water’s molecular mass is 18 (2 H, 1 O). 1 mol of water has a mass of 18g, so 1g of water has 3.34444×10^22 molecules (calculated by dividing Avogadro’s number, 6.02×10^23 by the molecular mass of 18).
FD&C Red #40 has a formula mass of 496, so by the same calculation, 1 g of Red#40 has 1.21371×10^21 molecules. That’s 1.2 sextillion molecules, in 10 drops.
In 1g of the solution of 10% Red#40, which is what Solutions and Pollution provides, there are 1.21371×10^21 particles of the molecule. If that is the mass of 10 drops, the cups have the following numbers of molecules of FD&C Red#4:
1: 1.21371E+20
2: 1.21371E+19
3: 1.21371E+18
4: 1.21371E+17
5: 1.21371E+16
6: 1.21371E+15
7: 1.21371E+14
8: 1.21371E+13
9: 0 (control)
The solution generally becomes colorless around cup 6, and students may think that it therefore has no red left in it. If you evaporate the water, though, you can see traces of the red in cup 6. These traces represent 1.2 quadrillion molecules, which illustrates just how small a molecule is.