Hot answers tagged

45 votes

Could one perform a test to determine whether water was warmed by a microwave rather than over a flame?

No, and this is one of the important facts about thermodynamics: Once a system has reached equilibrium, its "thermal history" (how it got heated in the first place) has been erased and ...
niels nielsen's user avatar
30 votes
Accepted

Since water is a molecule, can the aerosol sprayed through double slit form interference pattern?

No, not with a spray. The reason for this is that "sprays" are not isolated molecules. They are fine droplets, and the individual droplets are still vastly larger than a molecule - a ...
The_Sympathizer's user avatar
26 votes

Could one perform a test to determine whether water was warmed by a microwave rather than over a flame?

I agree with niels nielsen's answer at the spherical cow level, but I can see two factors that will be different in the real world. Whether they can be measured or not I do not know. Both come down ...
Loren Pechtel's user avatar
22 votes
Accepted

Can water at absolute zero still be liquid?

The phenomenon is called supercooling: A liquid crossing its standard freezing point will crystalize in the presence of a seed crystal or nucleus around which a crystal structure can form creating a ...
Roger V.'s user avatar
  • 58.2k
18 votes
Accepted

Will just the increase in height of water column increase pressure or does mass play any role in it?

At first, the conclusion seems absurd. You have a tank, which is open at the top of the pipe, that is comfortably holding 1000 L of water. Then you add just 1 L more, albeit in an unusual shape, and ...
Scott McPeak's user avatar
13 votes

Could a fish swim out of a sphere of water in a zero-gravity environment?

The experiment has been done. Zero gravity is not required. Fish are observed to jump out of bodies of water on Earth.
John Doty's user avatar
  • 20.1k
12 votes

Why isn’t $\rm H_2 O$ a primordial element?

The only chemical elements created in during the Big Bang are hydrogen (H), helium (He) and lithium (Li). This phenomenon is called Big Bang nucleosynthesis and current theories predict very well the ...
Mauricio's user avatar
  • 4,957
11 votes

Since water is a molecule, can the aerosol sprayed through double slit form interference pattern?

The deBroglie wavelength of a droplet of water can be calculated like any other particle: $$\lambda = \frac{h}{mv}$$ Where $h = 6.62607015×10^{-34} \frac{J}{Hz}$ - at $100 \frac{m}{s}$ a 1000 nm ...
Yakk's user avatar
  • 4,273
10 votes

Why does more ice melt slower than less ice?

Water has heat of fusion about $ H_{fus} =80~\text{cal/g}$, this means that for melting 1 gram of ice you need about 80 calories of heat. Obviously having more ice (monolithic piece or fragmented ...
Agnius Vasiliauskas's user avatar
9 votes

How would the volume of a drop of water (from a dropper) on the Moon and other bodies compare to one on Earth? (indoors of course!)

As per your comment below, there could be two aspects to your question, so I'll address both. According to this article, In the pendant drop test, a drop of liquid is suspended from the end of a tube ...
joseph h's user avatar
  • 29.1k
9 votes

Why does more ice melt slower than less ice?

The reason is still basically a variation of the square cube law. A pile or cup of ice cubes have more volume to melt relative to the effective surface area to perform heat transfer compared to if you ...
DKNguyen's user avatar
  • 9,129
8 votes

Could one perform a test to determine whether water was warmed by a microwave rather than over a flame?

According to Yakunov, A. V., Biliy, M. M., & Naumenko, A. P. (2017): There are so-called specific effects of microwaves. The first of them, although they have a thermal nature, cannot be ...
Blackhole's user avatar
  • 185
7 votes
Accepted

Breaking apart the surface tension of a water droplet

Such a capillary bridge will break when either surface tension overcomes adhesion or when gravity overcomes them both. For water, we expect the bridge to break before it separates by a distance ...
David Bailey's user avatar
  • 10.7k
5 votes

Will just the increase in height of water column increase pressure or does mass play any role in it?

The 1 liter pipe only encompasses a tiny fraction of the lid area of the tank. But is has caused a pressure of 972 kPa at the lid, and the lid is pushing downward on the liquid inside the tank with ...
Chet Miller's user avatar
  • 33.3k
5 votes

Why does water come out of a bottle in waves?

It doesn't always. But in general, if you get into a situation where more of it flowing causes less to flow, it's likely to come in waves. You have an air space. If you tilt the bottle enough that the ...
J Thomas's user avatar
  • 2,960
5 votes

Number of fog droplets in the air

Well the easiest solution is to say $L$ is inversely proportional to $n$ and $d^2$, so: $$ \frac 1 L \propto nd^2$$ or: $$ n \approx \frac 1 {d^2L} = 10^{10}\,{\rm m^{-3}}$$ and be done. A more ...
JEB's user avatar
  • 32.7k
5 votes

Since water is a molecule, can the aerosol sprayed through double slit form interference pattern?

They have performed interference experiments with big molecules, but not in forms of sprays, since then collisions and interactions between the particles would lead to their decoherence and loss of ...
drgetwrekt's user avatar
5 votes

Could a fish swim out of a sphere of water in a zero-gravity environment?

Some fish species are famous for swimming in free-falling water. a random video of salmon swimming up waterfalls If the body of free falling water is in a standstill with respect to the observer, this ...
fraxinus's user avatar
  • 7,876
5 votes

Conservation of water?

The number of water molecules is certainly not constant, because chemical reactions can create or destroy water. A simple example is metabolism of Glucose, which creates water. $C_6H_{12}O_6 + 6O_2 \...
Allure's user avatar
  • 20k
4 votes

Will just the increase in height of water column increase pressure or does mass play any role in it?

Can someone explain how just 1 litre of water exert so much pressure. Put succinctly, pressure (compressive equitriaxial stress, with the free surface serving as a reference) is exactly the ...
Chemomechanics's user avatar
4 votes

Bubbles formed in standing water in glass

It is more like bubbles coming out of fizzy water than boiling. Water often has air dissolved in it. If you let it sit, it can come out of solution. This happens at the surface, where the water ...
mmesser314's user avatar
  • 37.7k
4 votes

Why does the water go from left to right in this question?

The 'pressure' in Bernoulli's equation is the pressure at a point in a fluid. Any single fluid element exerts an outward pressure. The total pressure at a point is due to all the surrounding elements. ...
Sid's user avatar
  • 307
4 votes

Enthalpy of formation function of temperature

Doesn't the enthalpy of formation stay constant, while the sensible enthalpy of a species only changes with temperature? The temperatures in the table are the saturation temperatures (boiling points) ...
Bob D's user avatar
  • 70.3k
4 votes

Would seawater flow be affected by a magnet?

There will be weak diamagnetic and Lenz's Law effects, and a small Faraday voltage will be generated across the stream. Magnetic flow meters work by measuring this voltage. The flow velocity might be ...
David Bailey's user avatar
  • 10.7k
4 votes
Accepted

Why does water warm gradually when a faucet is opened?

Usually, the water stays in the pipe for hours before you open the tap. This would make the water stored in the pipe pretty cool. Now when you turn on the heater, all the water stored inside the ...
Dev Not Taken's user avatar
4 votes

Do high powered lasers refract differently than other light?

Lasers are light, so they refract the same as light. However, when light is travelling in a medium it might affect the medium. There are so-called non-linear self-lensing affects where the presence of ...
Jagerber48's user avatar
  • 13.6k
4 votes

Conservation of water?

You might have observed in a Science class at school a simple example of the number of water molecules changing , the electrolysis of water. An electric current is passed through water and oxygen gas ...
Farcher's user avatar
  • 94.9k
3 votes
Accepted

Why is this the "no bubbles" condition?

I think what the author might be implying is that if the surface integral of $\vec{\psi} \cdot \vec{n}$ ($\vec{n}$ denoting the unit normal) over the small sphere is non-zero, the sphere has expanded (...
kricheli's user avatar
  • 3,206
3 votes

What is the physical reason for why hot air holds more water vapour, and how does this relate to saturation vapour pressure?

It is correct, though the idea that air has a 'holding' rôle is, I think unhelpful. The air simply gives a background partial pressure. Consider first a liquid evaporating into the space above it in a ...
Philip Wood's user avatar
  • 35.3k
3 votes
Accepted

Bubbles formed in standing water in glass

Air in pits and crevices in the glass walls act as nucleation sites for the exsolvation of air in water. Air is less soluble in warm water than cold, so as the water warms up it becomes ...
niels nielsen's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible