Questions tagged [chemical-compounds]
115 questions
38
votes
2 answers
Why isn't the molecule of water linear straight?
When you see models of water you see something like this:
The hydrogens in the water molecule become negatively charged because the oxygen pulls electrons more. So why don't they repel and move to the opposite sides of the oxygen? Or just form on…
Trevor Blythe
- 499
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14
votes
2 answers
Difference between Reversible and Irreversible processes in Physics vs. Chemistry
In Physics a reversible process is defined as one in which the system can be returned to its initial conditions via the same path (along the PV Diagram), and every point along the path is an equilibrium state. An irreversible physical process is one…
Dhruv Upreti
- 143
14
votes
2 answers
Why exactly does molten NaCl explode, when it is poured into water?
Why does molten sodium chloride explode, when it is poured into water?
$\mathrm{NaCl}$ has high melting point, $1074\,\rm K$ ($801\,\rm^\circ C$). $\mathrm{NaCl}$ has molar mass $58.44\,\rm g/mol$, it has specific heat capacity $36.79\,\rm…
Sami M
- 385
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13
votes
3 answers
Can we call rusting of iron a combustion reaction?
In case of rusting of iron the chemical reaction is not fast enough. The oxygen used is not molecular oxygen from the atmosphere but it is the oxygen from water molecule. The reaction is not rapid and appreciable amount of heat is also not produced.…
Shinnaaan
- 1,455
13
votes
3 answers
What determines the color of a pure substance and is it possible to predict it?
I have always wondered why salt is white, water is clear and gold is, well, gold. What determines the color of a substance? Does it have something to do with the electrons? And is it possible to predict the color of a substance by looking at the…
Paul Houx
13
votes
2 answers
Silicon-based life
My question may not be suitable here, because it's more of astrobiology. Life as we know it is carbon based.
Is life based on silicon possible?
What would the conditions for habitability for silicon based life be?
Can both carbon- and…
user
- 657
10
votes
2 answers
How does stuff glow in the dark?
Many things have glow in the dark properties (glow sticks, paint, toys ..), and I am wondering what is the physics behind them. How do these materials store light energy and emit it later when dark?
What dictates the wavelength(s) of the glow? Is…
John Alexiou
- 40,139
9
votes
2 answers
Is sugar cube polycrystalline and why?
Sugar cube (see photo below) is made from white sugar granules (monocrystals) pressed together. Is it technically a polycrystalline and why? What forces act on neighboring sugar granules from the sugar cube --- are they the same as in naturally…
dust
- 141
8
votes
5 answers
Nano-particle or Molecule?
What's the difference between something being labeled a "nano-particle" or it being called a "molecule"?
cpuguru
- 181
8
votes
1 answer
Why does separating plastic from a cough drop create flashes?
I was tearing open individually-wrapped cough drops in the dark, and noticed that when I pulled apart two adhesive-joined pieces of silvery plastic film, small flashes of light were produced. It was not a reflection--it was pitch dark.
What causes…
ErikE
- 2,996
6
votes
3 answers
Why does a pitcher with lemon juice have foam, while one with pure water does not?
Whenever I pour water into lemon juice (pouring directly from the tap into the pitcher, not quietly along its edge) I get a foam on top:
The same pitcher with water (same water tap, pitcher, time between the water poured and the picture,…
WoJ
- 530
5
votes
1 answer
In chemical compounds, where does the "magic" come from in atomic "magic numbers"?
It is well known that atoms with a full electron shell are more stable, it is one of the first facts taught in a middle school Chemistry course:
"An element whose atoms have no electrons
outside filled energy levels is particularly stable…
user137661
5
votes
1 answer
Why soap bubbles are made of soap?
Why are soap bubbles made of soap? What I know is to have stability in bubble, waterproofing agents should me mixed, but soaps are water wetting agents, and water wetting agents will decrease angle of contact.
Can someone correct me?
Fawad
- 313
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5
votes
3 answers
Why is oil a poor conductor of heat?
Why is oil a poor conductor of heat as compared to metals? It is used in transformers to conduct heat to external fins. But is it ever used for heat insulation?
YJS
- 51
5
votes
1 answer
Density of Solid States of Compounds
One of the wonderful properties of water (as my high school biology teacher would say) is that in its solid form, it is lighter than its liquid form. This means that when temperatures drop below 0 degrees Celsius, the top layer of water on, say, a…
HDE 226868
- 10,934