Science Buddies: "Ask an Expert"

Hello,
I have been working on research so I can conduct a science fair project, but have had some difficulties in gathering materials and having the procedure down to the T. Here is my difficulties and my questions:

- How do I obtain both Bacillus subtilis and Pseudomonas fluorescens, culture them, and make a bacteria nutrient broth? I'm thinking I could get them from a probiotic, landfill, or online, but I am not sure what is the best way to obtain them and how to culture them and make the bacteria nutrient broth after I get my hands on the bacteria.
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- For obtaining HDPE (High-Density Polyethylene) and PLA (Polylactic Acid) can I just order sheets of these plastics online or is there a specific way to obtain them?
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- How do you test the plastics for tensile strength?
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- KOH = Potassium hydroxide, correct? If yes, how do I obtain .5 M of this, and how do I measure the M, which I assume means mol?
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- How and where do I isolate the plastic samples filled with topsoil and the bacteria nutrient broth?
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- How do I clean the plastic samples, and get them massed?
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- How do I titrate the KOH with .005 M HCl?
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- HCL is Hydrochloric acid, correct? If not, what is it?
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- How do I determine the amount of CO2 produced per mg of a plastic sample by titrating the KOH with .005 M HCl?
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- When it states ".005 M HCl" does this mean .005 mols of HCl?
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- If I use the t-test to test tensile strength, how do I conduct this?
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- Can the preparation of the bacteria nutrient broth, the culturing of the bacterias, and the whole process of this experiment/science fair project be done in my home?
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- I am assuming there would need to be security or safety precautions when done at home, so what would I need to ensure I am kept safe from any pathogens or harmful materials, and also to disinfect or clean the areas in my home when the experiment is done?

I know it's a lot, but this is something I have done a bit below the surface research into, and I am just so passionate about this project and would love to execute it.

Hello!

This sounds like a really interesting project! Can you give me an overview of what you are trying to find out from this experiment and write out the steps of the procedure that you have worked out so far? That will help me answer all of your questions better!

In terms of supplies, you can get both Bacillus subtilis and Pseudomonas fluorescens on the Carolina Biological website. The product page tells you what type of media the bacteria grow best in and what temperature to grow them in.

Bacillus subtilis:
https://www.carolina.com/browse/product ... ubmit=true

Pseudomonas fluorescens:
https://www.carolina.com/browse/product ... irect=true

You can grow the bacteria at home as long as you follow the proper safety precautions. Before you throw away the bacteria, you should soak it in 10% bleach (1 part bleach and 9 parts water) for at least 2 hours to make sure it’s dead. You should wash your hands thoroughly after handling the bacteria and clean your work space with 70% ethanol, 10% bleach, or a household antibacterial cleaning solution.

In terms of the plastics, the HDPE should be pretty easy to buy on Amazon. The PLA, on the other hand, is very expensive and harder to get because it’s a special biodegradable kind of plastic. PLA might not be the best option for an at home experiment.

You are correct that KOH is Potassium hydroxide and HCl is hydrochloric acid. You could get both of them on homesciencetools.com, but keep in mind that these are toxic and potentially dangerous chemicals so you would have to handle them extremely carefully. Titrating these chemicals at home might also be difficult. You would have to buy titration equipment, which can get expensive, and the procedure is hard to perform if you’ve never done it before and you don’t have an experienced scientist to help you.

After you send me more information on the goal of your project and the procedure you have written out so far, I can help you modify your experiment to make it easier for you to perform at home!

Hi, I just wanted to chime in regarding your questions about 'M' when you see it in reference to solutions. The M stands for molarity, and it means moles per liter.
So in order to make a 1 M solution of say, KOH, you need to know how many grams are in a mol of KOH. To do this, you need to know the molecular weight (grams/mol) of KOH.
Find a periodic table, and look at the atomic weights of the atoms in your chemical.

K weights 39 g/mol, O weighs 16 g/mol and H weighs 1 g/mol. Together, this means that one mol of KOH weighs 56g. (I have rounded these numbers, but you're unlikely to have a scale at home that can measure 0.01 g).

So, to make a 1M solution of KOH, you'd weigh out 56g of the KOH powder, mix it into some water, and then bring the volume of water to 1 liter total.
To make a 0.5 M solution, you'd use 28g of KOH in 1 liter.

Also, you can scale this down depending on how much you need. You could add 5.6 g to water and bring the total to 0.1 L, and that would still be 1 M KOH. (I just divided both amounts by 10). I hope that helps, looking forward to hearing more about this project.