We’ve all been subjected to silly, inane conversations in our life, often over a few drinks and usually at a bar. These conversations usually involve one person who claims that something that is clearly fiction is actually a fact, and no matter what, you just can’t convince them otherwise. The one example that comes to my mind is hearing someone declare that ten pounds of iron is heavier than ten pounds of cotton. No matter how many times you explain to your friend that a pound is the same weight no matter the substance, they just can’t seem to get it through their stubborn head.

But occasionally you’ll hear something that sounds really wrong, only to discover that it is actually true. This is the case with the sound of water. Yes, it’s true. It turns out that hot and cold water actually make different sounds when they are being poured.

I didn’t believe this myself when I first heard it from my friend at a bar several years ago, but it turns out he was right.

Hot water produces a higher-pitched sound when poured into a glass than cold water. The science behind this phenomenon relates to the viscosity of water. You’ve probably heard the term “viscosity” before in relation to the oil in your car, but it actually refers to the “thickness” of any liquid.

Yes, even water has a thickness.

Heat changes the viscosity of water, and all liquids for that matter, by energizing the molecules and making the liquid flow more, giving it a different sound when it splashes in a glass or cup. This is easier to see in other non-water liquids. Let’s go back to oil, for instance. Motor oil is somewhat thick when it comes out the can, but when it’s in your car being heated it’s transformed into a more fluid substance, which produces a different sound.

This is the kind of scientific fact that can be proven just about anywhere, even at the bar.