Density is defined as the mass per unit volume of a substance.
Questions tagged [density]
1013 questions
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Do the weights of two liquids not add when mixed?
I was given an interesting dilemma today. A co-worker saw me adding a liquid (Diisopropyl ethylamine AKA DIPEA) to a flask filled with another liquid (Tetrahydrofuran AKA THF). I needed to weigh out exactly 5 grams of DIPEA into the THF and so I…
Brian
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Do all black holes have a singularity?
If a large star goes supernova, but not enough mass collapses to form a black hole, it often forms a neutron star. My understanding is that this is the densest object that can exist because of the Pauli exclusion principle: It's made entirely of…
Carson Myers
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Why is jumping into water from high altitude fatal?
If I jump from an airplane straight positioned upright into the ocean, why is it the same as jumping straight on the ground?
Water is a liquid as opposed to the ground, so I would expect that by plunging straight in the water, I would enter it…
Conrad C
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Given that ice is less dense than water, why doesn't it sit completely atop water (rather than slightly submerged)?
E.g.
If we had a jar of marbles or something else of different densities and shook it, the most dense ones would go to the bottom and the less dense ones to the top.
(Image Source)
If I put a cube of lead in water it would sink all the way to the…
K-Feldspar
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Why does carbon dioxide not sink in air if other dense gases do?
Why does carbon dioxide not sink in air if other dense gases do?
We evidently do not suffocate by carbon dioxide sinking to the bottom of the atmosphere and displacing oxygen and yet there are gases that do sink. This is commonly a problem in coal…
chasly - supports Monica
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47
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6 answers
Why do rotten eggs float in water?
My mom told me that one can check whether an egg is rotten by sinking it in a glass of water. If it floats, then it is rotten.
I didn't find any explanation for this phenomenon. If anyone knows one, please answer.
prAnjal
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Will a penny ever stand still in the water at a certain depth?
Let’s say I drop a penny in the deepest part of the ocean having a certain depth. Would the penny become buoyant enough to stand still in the water, since the density of water increases with depth? Since the buoyancy of objects becomes greater as…
Justus Bozzi
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3 answers
Can ants walk on liquid mercury?
I'm not a physicist, but I was wondering:
Can ants walk on dense liquid like mercury and why?
Apolo
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Are black holes very dense matter or empty?
The popular description of black holes, especially outside the academia, is that they are highly dense objects; so dense that even light (as particle or as waves) cannot escape it once it falls inside the event horizon.
But then we hear things like…
Keerthi
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38
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9 answers
Why singularity in a black hole, and not just "very dense"?
Why does there have to be a singularity in a black hole, and not just a very dense lump of matter of finite size? If there's any such thing as granularity of space, couldn't the "singularity" be just the smallest possible size?
Per
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37
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Can I eat myself into a black hole?
This was a humorous thought experiment that occurred while chatting about black holes. The person that I was talking to assumed that a black hole required a specific density to be achieved. I pointed to the formula for the Schwarzschild radius. …
badjohn
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Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?
This is a problem I just started puzzling over, and I felt this would be a good forum to check my reasoning. So here are the relevant observations followed by my question:
Water achieves its maximum density at roughly 4°C. That is, water (including…
Excellll
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10 answers
Are there physical properties that can be used to differentiate stainless steel from copper in a home environment?
So the backstory is that I purchased a reusable drinking straw that is copper coloured, but is advertised to be stainless steel. That got me thinking about whether I could be sure it was one or the other without having access to a laboratory.
I saw…
Kolichikov
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What are some dense elements I can use for a demonstration?
I'm musing about how to give students an intuitive feeling about density by letting them lift a same sized volume of different materials, e.g. 1 liter of water, a $10 {\times} 10 {\times} 10 \, \mathrm{cm}^3$ cube of iron, lead etc. So far, the…
Jens
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How is water heavier than petrol, even though its molecular weight is less than petrol?
Molecular weight of petrol is so much higher than water,
but when it comes to physical property, weight, one litre of water weighs more than one litre of petrol.
How is it possible?
Olivier Lloris
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