Science Buddies: "Ask an Expert"

I am having trouble coming up with a hypothesis for my project, Which type of water is hardest. I am testing distilled water, tap water, and mineral water. I think mineral water is hardest but I don't know to state that and support it in a proper hypothesis. Could you PLZ help me fast.

Hi SirG.
Can you expand on why you are interested in "which type of water is the hardest?" As currently stated, I am not sure that there's a good way to generate a good hypothesis with it.

Please take a look at this:
https://www.sciencebuddies.org/science- ... hypothesis

In your case, the independent variable is the source of the water and the dependent variable is the mineral content (i.e. hardness of the water). However, what do you want to do with this information once you have it? (i.e. what prediction do you want to make with it? Ex. Is "harder" water better for plants? )

Good Luck and please post again if you have any follow-up questions.
Willey

I was using types of water as my IV. And how many soap bubbles form as my DV. I am using the project Shaking for Suds. Sorry for being unclear.

That's great!

To form your hypothesis then, let's try this:
- From the background section, you know that "Hard water interferes or reduces lathering (the formation of suds or bubbles)."
- Since you are testing for soap bubbles, we will put that as part of the expected "results" in the second part:

So, an example hypothesis may be:
"Bubble formations is dependent on the hardness of the water. As the water hardness level increase, the amount of bubbles formed will decrease."

I hope that process make sense. Please make sure to make adjustments to the above to suit your own experiment / hypothesis.
Good Luck!
Willey

Thank you so much. That example gave me a perfect idea.

I am two thirds done with it, but I am still curious about why hard water produces less bubbles than the other softer water types.

Excellent!
The answer, as you probably guessed, isn't quite straight forward. (In fact, I think folks have been using this topic for their PHDs for a long time now ) At any rate, my understanding / hypothesis is that the harder water (with its higher mineral content) makes it difficult for the bubble to maintain surface tension. Here's a couple of additional article / site that you might want to check out:

https://physics.stackexchange.com/quest ... oap-bubble
https://physics.aps.org/articles/v9/21

(Please try these search terms in google as well: "soap bubble physics", "soap bubble surface tension")

It sounds like you have found a great follow-up project!
Good Luck with your experiment and Have a great weekend!
Willey