Science Buddies: "Ask an Expert"

Hi Science Buddies,
I carried out the soap making experiment and now my problem is that I am not sure what the PURPOSE of this experiment is or how to write the HYPOTHESIS.
There are a few paragraphs provided on the website about it:

Abstract: "You will carry out the chemical steps needed to transform coconut oil into a usable bar of soap, and purify it with salt to measure how its pH changes with its purity."
Objective: "Make your own soap by mixing coconut oil with sodium hydroxide and demonstrate increased soap purity as you follow steps to purify it with salt (sodium chloride)."

But I am very confused about both of the above passages.

• Is our PURPOSE to demonstrate the process of making soap?
• According to the title, we are going to learn about soap synthesis through experimentation. So is our purpose just to learn about soap synthesis?
• Shouldn't there be a more specific purpose?
• So we are only doing this experiment to help understand and learn what soap synthesis is?

I wrote a purpose and a hypothesis before doing the experiment:
- Purpose: To find the soap that cleanses at the highest level while being gentle.
- Hypothesis: pH 8-10 is the most suitable for soap.

After doing the experiment I found that the experiment did not match the purpose and my hypothesis seemed very pointless and unnecessary.

This is our procedure:
• Place 10 mL of coconut oil and 15 mL of 3-M sodium hydroxide solution into a 100-mL beaker.
• Heat the mixture to a gentle boil.
• Keep stirring it until all of the water has evaporated.
• Remove this beaker from the heat and allow it to cool.
• Using the pH paper, test the pH of the crude soap and record
• Add 15 mL of distilled water to the crude soap and stir it
• weigh 15 g of sodium chloride and put it in a beaker.
o Add 50 mL of water and stir until dissolved.
o Heat the salt solution until it is almost boiling.
• Add the hot sodium chloride solution to the soap mixture.
• Break up lumps of soap
• Cover the beaker containing the soap mixture with cheesecloth and pour the liquid into a clear plastic cup. (Decanting the liquid.)
• Measure the pH of the soap with a new pH paper.
• Record the pH in your lab notebook. Call it Washed 1 time.
• Repeat steps 9–14 two more times.
• Record the pH after each wash. Call the pH readings Washed 2 times and Washed 3 times.
• Repeat the above steps fir different types of soap

I made three soaps, all using coconut oil and sodium hydroxide and sodium chloride. I washed each soap twice with salt and the final result was that all three soaps were at pH 8

Do you have any suggestions for a better PURPOSE and HYPOTHESIS? Or is there a more detailed explanation for this? I really need help, please get back to me as soon as possible, thank you very much!


[Administrator note: Project link: https://www.sciencebuddies.org/science- ... -make-soap ]

Hello,

This sounds like a fun project! Your question about the purpose and hypothesis for this project is very understandable because the procedure as written doesn't have any independent variable. This means you're not testing the impact of changing something in the procedure. It's more of a project than an experiment.

However, the project does provide some suggestions of independent variables you could test such as which oil makes the best soap or how many washes are needed to achieve the desired pH of the soap. For example, you could repeat the experiment using 1-2 other oils/fats besides coconut oil keeping all other things constant and then develop a methodology to test how well the different types of soap clean. In this example your purpose would be "to determine the best oil for making soap" and the hypothesis may be that "coconut oil soap provides the best cleaning performance for marker stains on hands."

Here is a good resources of writing a hypothesis:
https://www.sciencebuddies.org/science- ... hypothesis

Audrey

Thanks a lot!!