7
votes
2answers
68 views

Practical (maybe naive) question on boiling water

I put a glass bottle in a big pot, bottleneck up, I fill both pot and bottle with very hot water. The bottle is submerged except a few cm of the bottleneck and filled to the brim so some water ...
50
votes
7answers
6k views

Will a blanket warm you if you are underwater?

Suppose a man falls into very cold water and gets their foot stuck under a heavy rock. Fortunately, his head is above water and someone is able to call for help. The paramedics want to keep him warm ...
6
votes
3answers
385 views

Hot water freezing faster than cold water

This question has puzzled me for a long time. There is already a question like this on Physics.SE. John's answer to the question seems quite satisfying. But when I googled the cause I found this and ...
5
votes
2answers
194 views

Why does evaporation take place? [duplicate]

I was looking at at puddle when I thought that this puddle will evaporate tomorrow but then it occurred to me that the boiling temperature of water (aka to turn into gas) is $100$ degrees under 1 ...
2
votes
2answers
53 views

Reducing the evaporation of water at room temperature

Water drops kept on different surface evaporate after a few minutes. How can I reduce the rate of evaporation of these drops? Can I add some additives which suppress evaporation?
0
votes
1answer
47 views

Exception to weight of hot vs cold water?

I have seen the various posts regarding the comparison of weight of heated and cold water.But is there any contradiction?I live in really hot conditions and as such tap water literally 'boils' ...
14
votes
1answer
330 views

Why does a water drop on a hot plate at $150^o C$ evaporate faster than on a plate at $200^o C$?

I recently read that: "A drop of water landing on a hot plate at $150^o C \:(300 F)$ evaporates in a few seconds. A drop of water landing on a hot plate at $200^o C \:(400 F)$ survives a whole ...
3
votes
1answer
648 views

Behavior of water at temperatures above 100°C

Assuming you have container with heat insulation (something like boiler). You can store water at any temperature below 100°C. At these conditions, you can drill a hole into container and store water ...
7
votes
2answers
341 views

Why is the absolute zero a rational number in Celcius?

From the question "Why is the absolute zero -273.15?" I understood that 1°C is the 100th part of the difference of melting and boiling temperature of water (this is my high school physics, maybe there ...
5
votes
3answers
4k views

Does wrapping a wet paper towel around a glass bottle really speed up the cooling process?

There are claims like this one that you can improve the cooling speed of beverages when you put them wrapped in a wet paper towel inside the refrigerator/freezer. I've just tried it by myself and ...
21
votes
9answers
4k views

How can water evaporate at room temperature? [duplicate]

Boiling point of water is 100 degree Celsius. The temperature at which water in liquid form is converted into gaseous form. Then how it possible for water to evaporate at room temperature?
-2
votes
2answers
107 views

If a planet were cut in half but stayed hemispherical, how hot would the ocean on the flat side be? [closed]

Some time ago I asked a question about gravity on a hemispherical planet. What would gravity be like on a hemispherical planet? Would the water all boil away at first, quickly cooling the core of ...
4
votes
2answers
202 views

Why does my kettle only make a noise when it is turned on

Almost as soon as I turn my kettle on it starts to make the familiar kettle noise, yet very shortly after turning off the power the boiling noise stops and the kettle is totally silent. The ...
1
vote
1answer
121 views

Psychorometric equation : calculation of dew point

I would like to calculate a dew-point temperature having wet and dry bulb temperatures and atmospheric pressure. I have the equation, but this equation uses following coefficients: A: 6.116441 K: ...
0
votes
0answers
41 views

Optimal temperature for Mpemba Effect

Is there an pptimal temperature for the Mpemba Effect? Is there an optimal initial water temperature for speedy freezing? If so, what is it? If a specific example is needed: There is a 100 milliliter ...
27
votes
7answers
3k views

Is it possible to “cook” pasta at room temperature with low enough pressure?

It is known fact, that boiling point of water decreases by decreasing of pressure. So there is a pressure at which water boils at room temperature. Would it be possible to cook e.g. pasta at room ...
2
votes
1answer
1k views

Estimate temperature and pressure of steam in a pot of boiling water

Suppose we have a pot of known dimensions filled to level L with boiling water on a stove, covered by a lid with a vent of known dimensions. Given the steady-state temperature of the stove (bottom of ...
4
votes
3answers
425 views

Why is the absolute zero -273.15ºC?

I can't find an answer of why the lowest temperature is -273.15ºC. Is it deduced theoretically or is it experimental? An explanation is that when any gas volume tends to zero, the temperature will be ...
3
votes
1answer
1k views

Time required for water to freeze

recently I was wondering if there is any specific formula in order to calculate how long it takes for certain liquids to freeze (especially water). I know this depends on: the volume of the liquid, ...
0
votes
1answer
194 views

Does brown but transparent swimming pool water heat significantly faster than western style highly chlorinated pools?

Eastern European swimming pools are often brown tinted water. i was told it was the color of the chemical to keep the pools clean, but who knows. These pools did not smell unsanitary and may have even ...
1
vote
1answer
327 views

Does increasing the density of a solution decrease the rate of temperature change?

I did an experiment to compare whether salt water (5% concentration of salt) or fresh water of the same volume took longer to heat up to a certain temperature. We found that salt water took longer to ...
8
votes
2answers
3k views

273 + degree Celsius = Kelvin. Why 273?

Temperature conversion: 273 + degree Celsius = Kelvin Actually why is that 273? How does one come up with this? My teacher mentioned Gann's law (not sure if this is the one) but I couldn't find ...
5
votes
1answer
253 views

How do I measure the temperature of a tiny water droplet?

How do I accurately (+/- 0.1 degrees Celsius or better) measure the temperature of a small (5 to 50 microliter) water droplet without noticeably affecting its temperature? The mass of a thermistor or ...
2
votes
2answers
2k views

Why I will feel colder when I get out from a swimming pool? [duplicate]

A friend of mine told me that because water heat capacity is higher. He also mentioned that it was similar to alcohol on skin effect. Assume that there are 3 situations. 1. I did not get wet 2. I got ...
30
votes
2answers
5k views

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 ...
1
vote
1answer
289 views

Calculating temperature of water in the freezer

Assuming water volume ($V$), initial water temperature ($T_0$) and environment temperature ($T_e$) are known, what is the easiest way to calculate temperature of water in given time ($T$)? For the ...
4
votes
2answers
2k views

Why are refrigerators 4 degrees and freezers -18 degrees?

I assume that the refrigerator's temperature of 4 degrees has something to do with the fact that water is densest at that temperature. Does that inhibit microbe growth? But what about the freezer, ...
6
votes
1answer
599 views

Why does blowing on someone who is wet feel colder than on someone who is dry?

The title says it all. If I'm standing in the wind and I'm wet, I feel much colder than when I'm dry. This is true no matter how warm or cold the water. Why is this?
1
vote
1answer
921 views

How does liquid convert to gas on getting thermal heat energy?

Say for example, when we heat, water converts to steam gas. How does it happen? What happens underneath giving rise to breaking of bond between molecules in liquid state and spreading them in gas ...
6
votes
2answers
792 views

If you stop water from expanding, will its temperature stop rising?

Water expands when it heats up. If you heat water in a container that prevents it from expanding, will its temperature top out -- maybe around the boiling point? And if not, will it still turn to ...
20
votes
4answers
36k views

How does water evaporate if it doesn't boil?

When the sun is out after a rain, I can see what appears to be steam rising off a wooden bridge nearby. I'm pretty sure this is water turning into a gas. However, I thought water had to reach 100 ...