Science Buddies: "Ask an Expert"

Hello so I am struggling on this specific project (https://www.sciencebuddies.org/science- ... #procedure) and was wondering if anybody could help me or answer some of my questions.
1. In step 3 it states" Pour a small amount of your your first solvent (water) into the 100 mL beaker". I wondering if the amount that I pour for the first solvent should be the same when I pour the other solvents?
2. how do I determined which one is best combination? Is it based on the how many color there are?
3. I have not been taught the Rf value yet in school and was wondering if anyone is willing to explain to me. I am having trouble understanding it.
4. For step 7 part a when it says to measure the distance the solvent what does it exactly mean? How would I measure the distance the solvent travel? And it also tells me to measure how far the component traveled. Would I measure from the 2cm mark or from the end?

Thank you to anyone in advance that answer my questions :D

Hello,

This looks like a fun project!

1. The amount of solvent in the 100ml beaker is not very important as long as there is enough for the chalk or paper to soak up. If the beaker was dry before the solvent reached the top of the chalk or paper it would effect your results.

2. To determine which combination of solid phase and solvent separated out each marker brand the best you would compare the Rf values. A higher Rf value would indicate better separation.

3. There is a nice explanation of Retention Factor (Rf) on the Background page (https://www.sciencebuddies.org/science- ... background). It is a calculation that shows how far your ink component traveled up the chalk/paper relative to how far the water has travelled up the chalk/paper. A high Rf value indicates that the ink component traveled further up the chalk/paper than a lower Rf value.

4. To measure how far the solvent travelled you would use a rule to measure the distance between your 2cm pencil line and the solvent front. To measure how far the component travelled you would measure the distance between your 2cm pencil line and the component dot. There is a diagram on the Background page (https://www.sciencebuddies.org/science- ... background).

I hope this helps and have fun testing!

Audrey

Thank you so much for replying. I was wondering what would be a good way to show my data that I gathered from this project?

Tiffany

Hi Tiffany,

Since you'll be repeating this experiment for each brand of marker three times you could calculate the average Rf value for each combination of marker brand, stationary phase (paper or chalk) or different solvents (water, isopropyl alcohol, acetone) and chart these to show which combination had the best separation. You could then use what you know about polarity to draw conclusions about the different marker components.

Audrey