Science Buddies: "Ask an Expert"

Hello everyone. You can call me "scienceonfire". I'm one of those pour souls who don't come up with novel ideas for science fair projects in a flash.

Anyway, I decided on the topic "Do acidic compounds have any effects on hair?", but I'm in a rush, for the project is due in about two to three weeks, and the topic is due in two days.

I'm planning to put a strand of hair in a cup of the acidic compound (such as vinegar), a strand of hair in a cup of a control liquid (water), and a strand of hair in a cup of base liquid (such as soap water). I may need three of each cup. After that, I just let the cups lie while I record data.

But here's my problem. Can you give me ideas on how to see how the liquid a strand of hair is in is affecting it? This is an aspect in the topic that I'm not confident at (which results in no approvals from my parents, and boy, do they want novel science fair projects).

So... can anyone be of help? I'm in a desperate situation here. Thanks.

You might already be beyond this stage, but we have a topic selection wizard which can be helpful:
https://www.sciencebuddies.org/mentorin ... _guest.php

As for the experiment you mentioned, it sounds pretty good to me. You might want to change the title - it only mentions acidic compounds, but the experiment uses acids and bases. The bases might be more interesting to people, because everyone washes their hair and they might be curious about all those claims that shampoo companies make (thicker, stronger hair etc etc etc). You could measure the dry weight of the hair before and after soaking. You could also measure the strength of the hair before and after by measuring how much weight a single strand can support before breaking.

Hi scienceonfire,

I would also add that if you have light microscopes available to you at your school, you could also check to see if the structure of the hairs are affected by the different solutions. You could microscopically examine the hairs before and after your experiment and see what differences - if any - you observe.

This would require you to do a bit of background reading on what the structures of hair are - but this should be relatively easy to find.

The strength testing that ChrisG mentioned is an excellent idea.

Good luck with your experiment, and please keep us informed of your progress.

Best wishes,
Geoff.

Okay. The Science Fair is coming up in a week, and the project is due next Monday. The experiment's finished... and I had to switch to string, since it was a little easier to experiment with (especially if you use spring-scales). Anyway, I have to start my research, and I don't know where to start. I kind of distrust search engines, for they never provide real help. So, here's the question that I hope you can provide websites with the answer for:

Why is it that acidic and basic liquids weaken string more than water does?

BTW, I used hydrochloric acid for acid and bleach for the base. The results showed that acid and bleach weakened string more than water did, although the results did not prove that acid weakened the string more than the basic liquid did, and vice versa.

Thanks.

Hi - glad to hear that you've made progress on your project.

What kind of string did you use (for example, cotton or nylon)?

Very generally: acids and bases contain highly reactive ions (H+ for acid and OH- for bases) that tend to change the structure and composition of organic molecules. These reactions tend to break organized groups of large molecules into unorganized groups of smaller molecules, which weakens the material. Neutral water with a pH of 7 is typically not as reactive with the types of organic molecules that are used in string. (did you test the pH of your water?)

Anyway, the string that I used is made of cotton.

So... while the information is useful, I feel like I could use more. Could I please have a start on what websites to search for?

Glad to hear you're hungry for more. Here is a good place to start reading about the composition of your string and the reactions taking place in your experiment:

http://www.fibersource.com/f-tutor/cellulose.htm

You'll see that cotton fiber is almost pure cellulose, and if you look under "Reactions of Cellulose" you'll find a section on "hydrolysis" which describes the basic details of acid and alkali reactions with cellulose.

If you want more info than that, try searching in google for web pages with terms like "cellulose hydroloysis." You'll find that there are some interesting commercial applications for those reactions.