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Questions tagged [phase]

An entity of a material system which is uniform in chemical composition and physical state. This tag should be applied to question regarding chemical and physical properties of phases, systems of phases and also phase transition processes.

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22 votes
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Why must both the critical temperature and pressure be exceeded to achieve the supercritical phase?

The characteristics and properties of supercritical fluids and the associated vapor-liquid critical point are well established. One thing that I've always been curious about, though: what is the ...
hBy2Py's user avatar
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20 votes
1 answer
9k views

Why can't helium be solidified at 'ordinary' pressures?

According to the UC Davis ChemWiki Chemistry of Helium, helium has a comparatively unusual property, specifically: Helium is the only element that cannot be solidified by lowering the temperature ...
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15 votes
3 answers
32k views

Why is active mass of a pure solid or liquid always taken as unity?

Active mass is defined as the molar concentration ie. number of Gram-moles per litre. My book then wrote Active mass of pure solid/liquid is always 1 . The book reasoned that Molar ...
user avatar
51 votes
9 answers
518k views

Why does ice water get colder when salt is added?

It is well known that when you add salt to ice, the ice not only melts but will actually get colder. From chemistry books, I've learned that salt will lower the freezing point of water. But I’m a ...
cspirou's user avatar
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28 votes
2 answers
6k views

What happens if you cool water in a container too small for it to freeze?

Freezing a full bottle of water tends to shatter the glass bottle. What if you used something tougher than glass, like diamond? What would happen if you kept dropping the temperature, but restrained ...
tom's user avatar
  • 537
97 votes
7 answers
68k views

Is toothpaste solid or liquid?

My teacher didn't answer this properly: Is toothpaste solid or liquid? You can't say toothpaste is a solid because solid material have a fixed shape but toothpaste doesn't. However, you can't say ...
Simon-Nail-It's user avatar
1 vote
3 answers
25k views

Sublimation of Iodine

Why does iodine sublime? I have researched it myself and I have got the same answer; it sublimes because it directly converts from solid to gas. But why don't bromine or chlorine also sublime?
user247833's user avatar
16 votes
4 answers
146k views

During phase change in matter, why doesn't the temperature change?

I was working on something in school and came across the question: Why does the temperature not change much during a phase change? I'm really not sure why this happens in matter and I couldn't ...
GDP2's user avatar
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7 votes
3 answers
9k views

Is a liquid in a container always in equilibrium with its vapour?

This is essentially a question about the meaning and significance of the term vapour pressure (or vapor pressure if you're American). From what I understand a liquid in a container will have a certain ...
RobChem's user avatar
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28 votes
4 answers
4k views

How many molecules does it take to have a phase?

A single molecule can't be solid, liquid or gas. It's just a molecule. A mole of something can be any of the three. So, how many molecules does it take for phases to be meaningful? I realize that ...
terdon's user avatar
  • 395
27 votes
2 answers
104k views

Why does water evaporate at room temperature?

When water temperature reaches $100\ ^\circ \mathrm{C}$, the molecules get so excited that the hydrogen atoms lose the bonds to the oxygen atom and therefore the water starts to become gas. I get that,...
nFu9DT's user avatar
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16 votes
5 answers
46k views

Difference between state of matter and phase

What is the difference between state of matter and phase? This site said that: Phases are different from states of matter. The states of matter (e.g., liquid, solid, gas) are phases, but matter ...
Joe Academia's user avatar
15 votes
4 answers
3k views

Room-conditions supercritical fluids?

Are there any reasonably obtainable supercritical fluids that I could, say, run my hand through? Wikipedia makes it sound like there are plenty of room-temperature ones, but no room-pressure fluids.
Nathan Ringo's user avatar
4 votes
1 answer
1k views

Why do gases need to be cooled to liquefy/solidify?

My book states: Gases do not liquify on compression only, although molecules come close to each other and Weak forces operate at a maximum. Why is it that we cannot just keep on compressing gas ...
Shivay Vadhera's user avatar
2 votes
3 answers
1k views

melting and boiling ...really equilibrium? [closed]

Why are melting and boiling considered equilibrium processes even though the amount (concentration) of both phases keep changing i.e from solid to liquid and so on?
Oshoo Patel's user avatar
1 vote
1 answer
1k views

When it rains, it puddles. Spilled salt cycles between wet and dry with humidity. Is this akin to a phase change?

I have some spilled un-iodized table salt (NaCl). It is very humid where I live, and when it gets very humid for a few days, the salt absorbs so much water that it becomes a puddle of (probably) ...
uhoh's user avatar
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55 votes
2 answers
13k views

What is the pH of ice?

The pH of pure liquid water depends on temperature. It is about pH = 7.0 at room temperature, pH = 6.1 at 100 °C, and pH = 7.5 at 0 °C. What happens to the pH (or to the ion product) of pure water ...
Horatio's user avatar
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17 votes
1 answer
88k views

What is the melting point of diamond?

Textbooks and the online reference differ about this and there are more than two answers.
user3286264's user avatar
14 votes
4 answers
4k views

Is it possible to boil a liquid by just mixing many immiscible liquids together?

In open air, when vapour pressure reaches 1 atm, boiling takes place. I read that if we add two immiscible liquids together, the total vapour pressure of the 'mixture' is close to $p = p^*_A + p^*_b$,...
TheLearner's user avatar
  • 1,241
13 votes
1 answer
13k views

Are there any gases more dense than liquids?

Inspired by Is there any type of liquid, other than mercury, that PTFE teflon is known to "float" to the surface in?, are there gases that are more dense than liquids? (So bubbles would sink ...
Gyro Gearloose's user avatar
11 votes
1 answer
7k views

Significance of phase of atomic orbitals

I am learning about orbitals and bonding and antibonding MOs. So far, I know that when you combine s orbitals, you form both bonding and antibonding MOs- bonding when the wavefunctions are added in ...
Meep's user avatar
  • 1,697
9 votes
3 answers
224k views

How can melting point equal freezing point?

I don't understand how the freezing point of a substance is the same temperature as the melting point of the same substance. For example, if liquid water freezes at 0 °C how can ice also melts at 0 °...
jaykirby's user avatar
  • 689
8 votes
4 answers
5k views

Is glass an amorphous solid or supercooled liquid?

I have been informed that glass is a super-cooled liquid and is also considered to be an amorphous solid. Can it be both and, if not, what category does it fall into?
Prabhdeep Singh's user avatar
8 votes
3 answers
1k views

Can precipitation occur in states of matter other than liquids?

This answer to Are precipitation and crystallization both analogous between chemistry and meteorology? discusses the history and use of the term "precipitation" in chemistry. From what I ...
uhoh's user avatar
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7 votes
1 answer
8k views

Why does color of halogen deepens and the boiling point decreases down the group?

Why does the color of the halogens deepens as we go down the group? also why there is a change in physical state of halogens down the group? \begin{array}{c|c} \mathbf{Gas} & \mathbf{Color} \\\...
Nilay Ghosh's user avatar
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7 votes
2 answers
704 views

What happens to boiled (BMIM)PF6?

[BMIM]PF6, or 1-butyl-3-methylimidazolium hexafluorophosphate, is commonly used as an ionic liquid. As has been shown by the accepted answer to this question, sodium chloride that has been made to ...
user73910's user avatar
  • 1,264
6 votes
1 answer
1k views

Phase abbreviations for non-aqueous solutions

When writing a chemical equation, how do you indicate that a chemical is dissolved in a non-aqueous solvent? For example, it would be inappropriate to write X (aq) when X is dissolved in benzene, ...
Sam Lewis's user avatar
5 votes
1 answer
3k views

Boundary lines in phase diagrams and the lever rule

My first question is: What exactly happens on a point situated on a line? Or on a point such as E in this figure? Does point E mean that the $\delta , \gamma + \delta , \delta + \epsilon , \gamma + \...
DLV's user avatar
  • 813
5 votes
4 answers
2k views

Phase diagram for first 10 elements

I've been looking on the net for a reference which shows a phase diagram for elements at least from $\ce{H}$ up to $\ce{Ne}$. Specifically, I'm looking which of these elements can be solid or liquid ...
lurscher's user avatar
  • 199
5 votes
1 answer
639 views

Is it possible to have only liquid in a closed container?

I recently read an answer by Aman Rusia for this question: Is a liquid in a container always in equilibrium with its vapour? In it, they say that You can't have a container filled with only ...
Cyclopropane's user avatar
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4 votes
2 answers
924 views

Contact explosion of nitrogen triiodide

Nitrogen triiodide, on slightest physical contact, explodes to evolve dense purple fumes of iodine. Why does this phenomenon occur? video link - https://www.youtube.com/watch?v=2KlAf936E90
Nilay Ghosh's user avatar
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4 votes
1 answer
5k views

What defines matter's phase at room temperature?

So, a simple question: what makes neon a gas; what makes water liquid; what makes plutonium-238 a solid at room temperature? Of course, the phase is determined by the excitation of the molecules, but ...
Steven's user avatar
  • 151
3 votes
2 answers
1k views

Can water be liquefied or solidified just by adjusting the temperature, regardless of the pressure?

technically the line between liquid and solid phase would go a long way before hitting the y-axis, but the point is it will eventually. So the question remains, can any liquids, including water (with ...
user134789's user avatar
3 votes
1 answer
526 views

What are some examples of pure substances with no liquid state? [closed]

For example, A molecular substance that decomposes before melting, and under pressure can only assume a liquid state that doesn't contain the same molecules, for example a mixture of the elements of ...
Brian's user avatar
  • 1,201
3 votes
1 answer
2k views

Does the density of a liquid and gas phase of a substance(nitrogen or water) converge when reaching critical point

I know that the there is no difference in density in a liquid and a gas phase of a substance after the critical point. But I do want to know if this difference in density is more continuous or if it ...
einstein's user avatar
  • 133
3 votes
3 answers
3k views

Proof of Dynamic Nature of Equilibrium

Here is how my textbook proves that dissolution of solid in liquid is dynamic in nature. It considers the example of a saturated solution of sugar. It says that, Though the solution is in ...
DoubtExpert's user avatar
2 votes
1 answer
341 views

Depression of freezing point [closed]

Recently, I learnt that by adding a non-volatile solute to a solvent, the vapour pressure of the solution is decreased and consequently its boiling point. Facts and definitions freezing point: "The ...
Chemist's user avatar
  • 531
2 votes
1 answer
240 views

Phase stability of alcohols

Tert-butyl alcohol seems unusual among alcohols in that its melting point is high (25°C) while its boiling point is also still low (82°C). I am looking for more materials with phase-unstable liquid ...
ericksonla's user avatar
  • 1,700
2 votes
1 answer
25k views

Equation to calculate the triple point

Is there any equation that can calculate the triple point of a substance? Because a method for calculating the critical temperature and the Boyle temperature of a substance that I posted in another ...
KingChem's user avatar
  • 109
1 vote
1 answer
200 views

Can every chemical compound be melted?

Are there any chemical compounds that disintegrate (without going into other chemical reactions; let's say in a vacuum) before reaching a melting temperature?
piotrek's user avatar
  • 121
1 vote
3 answers
7k views

Why don’t all objects melt and liquefy when heated sufficiently?

Certain objects such as metals, glass, plastic, sugar etc. melt when heated to a certain temperature but other materials such as a piece of wood, paper, a piece of rock etc. do not. Why is that?
SRS's user avatar
  • 119
-2 votes
4 answers
12k views

What happens to the molecules of a liquid when it evaporates?

Let's say I spill liquid on some fabric or on a impermeable material like a countertop. Eventually, the liquid stops being a liquid and we say it has "dried", but what happened to the molecules? Did ...
Nathan's user avatar
  • 113
21 votes
1 answer
430 views

What happens when para-water ice is suddenly melted?

Background (hydrogen) In the case of recently liquified hydrogen (which is quite cold of course) it must be re-equilibrated before loading on to a rocket as fuel to avoid a sudden exothermic ...
uhoh's user avatar
  • 5,898
18 votes
3 answers
45k views

Why are water droplets shaped like that?

With nothing to do, I stared at the droplets that get condensed on the glass panel of my window. Upon examination, these droplets appear to be in some sorta pattern. There are big droplets as well as ...
most venerable sir's user avatar
16 votes
2 answers
12k views

Molten vs Liquid

When I start studying electrochemistry, I learn the words “molten” and “aqueous”. I don't have a problem for “aqueous”, but I'm a little bit confused about “molten”. For me, “molten” means melt, ...
Simon-Nail-It's user avatar
15 votes
5 answers
4k views

Why does liquid water form when we exhale on a mirror?

In the descriptions below, I always assume external pressure to be constant at 1 atm, the condition where daily observations are made. 1) When I exhale on a mirror, liquid water forms on the mirror. ...
TheLearner's user avatar
  • 1,241
14 votes
1 answer
509 views

Is helium-4 a liquid at zero temperature and zero pressure?

As far as I know, for all substances other than helium, if you extrapolate the solid-gas line on the phase diagram, it passes through the origin. That is, no matter how low the temperature is, you can ...
Brian's user avatar
  • 1,201
14 votes
2 answers
7k views

Burns from boiling water and steam

Why is a burn to the skin caused by steam more serious than a burn caused by the same amount of boiling water at the same temperature? The temperature is the same, which implies that the kinetic ...
StopReadingThisUsername's user avatar
12 votes
1 answer
1k views

Freezing point of oxygen-18 water

The freezing points of heavy water (3.8 °C) and tritiated water (4.49 °C) both seem to be well-known. I can't find anywhere that gives the freezing points of $\ce{H2^18O}$, $\ce{D2^18O}$, or $\ce{T2^...
Joseph Sible-Reinstate Monica's user avatar
12 votes
1 answer
865 views

Jahn-Teller Metal : The new state of matter

Recently it came in the news that scientists have discovered a new state of matter called Jahn-Teller metal. I tried reading up on it but couldn't understand it clearly. Please explain in simple ...
Binary Geek's user avatar
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