Slightly off-topic - There Chemistry in its Element podcast is a good listen. 15 mins every week talking about a different compound/element: https://www.chemistryworld.com/podcasts

I had a friend in school that noticed that fresh new batteries are much softer than old dead ones.

All of his devices had batteries with bite marks in them.

Similar neat trick: to tell if an egg has been hard-boiled, spin it on its side. A raw egg will immediately stop rotating, a cooked one won't.

Relevant: https://www.youtube.com/watch?v=HFDHFTffKTc [Spinning Eggs - Mr. Wizard's Supermarket Science]

I thought the trick was you spin the egg, then stop it - a raw egg will continue to rotate because the fluid inside is moving, but a cooked egg won't restart because nothing inside it is moving.

This link shows a hardboiled egg spinning on its end, but otherwise seems to agree with me, though it doesn't quite contradict you: http://www.planet-science.com/categories/experiments/magic-t...

Not sure for which batteries this works. After seeing that YouTube video some time ago, I tried to reproduce it at home with some AAA batteries. Didn't work.

It worked with normal AAAs for me. It's just quite nuanced. When dropping from the right height the empty ones on my wooden table tend to fall over, the full ones stay more still and upright with minimal bounce.

The paper says "zinc alkaline primary LR6 batteries"

> Alkaline AA batteries are one of the most common battery types [...]

Is this really true anymore? I use almost exclusively rechargeable batteries (NiMH & Li-ion & LiFePO4) our my household. Only very low power devices such as clocks run on alkaline batteries.

I buy 4 and 8 packs of rechargeables and 20 and 40 packs of disposables. I handle the rechargeables a lot more, but there are certainly more disposables by count present in my home.

I'm only switching to build-in li-po batteries, which hover seem to take over now.

Probable April Fools joke. Posted on March 31st.

I did blind tests and it totally worked.