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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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2answers
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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 ...
19
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1answer
4k 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 ...
84
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8answers
42k 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 ...
36
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6answers
394k 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 ...
15
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4answers
88k 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 ...
13
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5answers
23k 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 ...
13
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2answers
5k 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 ...
10
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1answer
2k views

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 ...
4
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1answer
505 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 ...
1
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2answers
541 views

Why all objects do not melt and liquefy when heated suficiently?

Certain objects such as metals, glass, plastic, sugar etc. melt when heated above a certain temperature but other materials such as a piece of wood, paper, a piece of rock etc. do not. Why is that?
15
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2answers
36k 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,...
4
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1answer
1k 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 + \...
3
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2answers
981 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 ...
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4answers
5k 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 ...
7
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3answers
3k 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?
5
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4answers
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 ...
4
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1answer
3k 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 ...
3
votes
1answer
916 views

What are the triple point pressure and temperature for pure cyclohexane?

Here is a video that demonstrates the interesting nature of the triple point of cyclohexane, so I tried researching on the internet for a phase diagram, but only found data from a manufacture where ...
3
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1answer
173 views

Reasons for existence of eutectic point for alloy systems

Why does a eutectic point exist for a system of alloy ? Why is it that there is such a definite ratio of composition at which this occurs ?
2
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1answer
171 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 ...
15
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1answer
61k views

What is the melting point of diamond?

Textbooks and the online reference differ about this and there are more than two answers.
9
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1answer
3k 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 ...
5
votes
2answers
518 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
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2answers
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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?
0
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1answer
68 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. Also consider the definition of the ...
28
votes
4answers
1k 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 ...
9
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2answers
17k 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 ...
10
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1answer
5k views

What is melting? Which bonds do we break to melt something?

To melt diamond, we have to break the covalent bonds, which we can consider 'intermolecular' because it is one giant molecule. To melt Methane, we have to break the van der Waals (intermolecular) ...
17
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1answer
8k 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 confuse about molten. For me, molten means melt, which means ...
2
votes
1answer
14k views

Why is the boiling point of water and ammonia so different?

Boiling point of water is 100 degrees Celsius, while boiling point of ammonia is minus 33 degrees Celsius, which makes 133 degrees difference. Now when we discuss value of boiling point, we also say ...
13
votes
4answers
717 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.
10
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3answers
148k views

How can melting point equal freezing point?

I don't understand how melting point = freezing point. For example, if liquid water freezes at 0 °C how can ice also melts at 0 °C?
10
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2answers
1k views

Can I pour a solution into another vessel with no air bubbles?

I have been trying to create a method to create a homogeneous agar solution. What are appropriate techniques to ensure homogeneous solidification of an agar-based aqueous solution? The new solution ...
8
votes
1answer
461 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^...
7
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0answers
330 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 ...
2
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1answer
8k views

What elements and/or substances without water are liquid at room temperature? [closed]

I was thinking about liquids, and I started to wonder theses related questions: 1) Besides mercury, what elements are naturally liquid at room temperature? 2) What naturally found family of ...
12
votes
1answer
394 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 ...
5
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2answers
307 views

Can all substances be supercooled?

With optimal conditions can we supercool any compound or is it that just water and a certain set of others can be supercooled? If not, why?
5
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1answer
128 views

What are appropriate techniques to ensure homogeneous solidification of an agar-based aqueous solution?

I am making a T1 weighted phantom for an MRI project. I'm trying to see if I can calculate how much a persons head heats up during an MRI scan. It consists of distilled boiling water, $\pu{7 g/L}$ ...
4
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3answers
817 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 ...
4
votes
1answer
259 views

Multiphasic liquid “flotation” experiment

I'm trying to create an experiment where two immiscible liquids are mixed and are then separated by density. Most of the container is occupied by the lighter liquid, and the small amount of heavier ...
3
votes
2answers
1k views

At what temperature (in kelvin) are most of the elements on the periodic table liquids?

This question is out of pure curiosity. At what temperature are a majority of the elements on the periodic table in a liquid state/phase of matter? For the purpose of this question, assume the ...
3
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3answers
3k 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 ...
14
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3answers
22k 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 ...
8
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1answer
917 views

Open Database of Phase Diagrams?

Is there some kind of database that has information about phase diagrams of different substances? I'm mostly looking for phase diagrams of elements (silicon, iron, hydrogen, etc.) because I'm trying ...
7
votes
1answer
174 views

Why so few fluid phases?

Taking a look at the phase diagram of water By Cmglee - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14939155 I see ice phases as much as up to 'Ice XI', but only one '...
7
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1answer
5k 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} \\\...
7
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1answer
13k views

Caffeine boiling and melting points

According to both caffeine's pubchem page and chemspider page its boiling point lies at 173°C and its melting point at ~235°C. How can it melt at that temperature if it already sublimated at 173°C? Or ...
6
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1answer
1k views

How does ice melt?

I know that when water freezes, it forms a crystalline structure created by the hydrogen bonds between polar water molecules. Also, I know that during a phase change, the potential energy of the ...
5
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3answers
4k views

Why is ice less dense than water?

I know the traditional explanation, which says that ice has large spaces between $\ce{H2O}$ molecules because hydrogen-bonding gives it an open structure. But what does the open structure have to do ...