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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Does water expand on freezing more than any other known substance?

Several substances expand on freezing. Gallium expands 3.1% and bismuth 3.3%. However, both of these are much less than water which expands 9%. Is there any substance that expands more than 9% on ...
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-1 votes
2 answers
46 views

Spontaneity criterion for phase transformations and chemical reactions [closed]

Why is the Gibbs free energy (G) considered a spontaneity criterion for phase transformations and chemical reactions? Why are other thermodynamic parameters such as enthalpy (H), entropy (S), and ...
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-1 votes
3 answers
152 views

Why does equilibrium of ice and water only exist at 273K at normal pressure?

I am a high school student and I am a little confused in the concept of spontaneity of a reaction and how equilibrium works for a reaction, I got some confusions: Let's take example of freezing of ...
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10 votes
1 answer
788 views

Are molecules exchanged between a solid and liquid in equlibrium?

In Vapor-Liquid Equilibrium, it is my understanding that molecules exchange between the gas and liquid continuously; even when no difference in temperature or partial pressure exists. Regarding Solid-...
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6 votes
1 answer
250 views

Water getting hotter once frozen?

I packed a fridge with temperature sensors and took over the temperature control in order to have extra cold beer. One of those sensors is submerged in the middle of a container containing a 4.5% ...
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1 vote
0 answers
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What polyatomic substances have the lowest known freezing points at standard pressure?

At standard pressure, helium never freezes, so that's clearly the coldest liquid—but it's also a monatomic substance. Diatomic hydrogen freezes at 13 K. Neon freezes at 24 K. And then the next coldest ...
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-3 votes
1 answer
69 views

Melting and Freezing [closed]

Ok so I needed some help understanding one concept, for eg:- we are in an isolated room that has a room temperature of 0 degrees Celsius. And I bring in some water in the room, so eventually it will ...
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1 vote
2 answers
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Explaining the process of boiling a liquid

I am confused by the thermodynamic definition of boiling. It is stated that boiling occurs when the vapor pressure of a liquid is the same as the ambient atmosphere. Now suppose we deal with an open ...
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  • 114
2 votes
0 answers
42 views

Interpreting Ternary Phase Diagram Stoichiometry

I am trying to locate the lowest-melting mixture in a system of three nitrate salts: sodium, potassium, and calcium nitrate. I have the relevant ternary phase diagram, but I am unsure exactly about ...
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3 votes
1 answer
163 views

Doesn't the eutectic diagram violate Gibbs's phase rule?

EDIT: As the question hasn't attracted any answers, I tried to put in more detail. Gibbs's phase rule for a 2 component system at constant pressure says that $F=3-P$, i.e., that the number of degrees ...
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0 votes
0 answers
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Solubility of multiple solutes and limits of solubility during freezing

I'm interested in modeling the freezing of solutions of water and I'm not really sure what happens in water after the solubility of a given material is reached. I know that as ice crystals form they ...
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  • 217
2 votes
0 answers
48 views

What is the difference between milk and cream that causes disparate result when freezing and thawing?

If you freeze milk and then let it thaw/melt again you just need to shake and it is more or less indistinguishable from unfrozen milk. That is not true for cream - after letting frozen cream (40 % fat)...
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  • 189
1 vote
2 answers
295 views

How does water sublimate at normal atmospheric pressures/conditions (i.e., without a phase boundary between solid and gas)?

I remember my high school chemistry teacher stating that water could sublime under normal atmospheric conditions that would exist in e.g., Lancaster County, PA, where Amish would hang clothes to dry ...
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0 votes
1 answer
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Mechanism of successively melting ice with table salt [closed]

Hi I was reading about how regular sodium chloride in itself can melt ice outside, for example ice on roads during low temperatures. However, I am unsure about the exact details, as I have found some ...
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  • 114
1 vote
0 answers
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Will a liquid-liquid emulsion and the separated emulsion have same volume?

Let's assume that there is no dispersed gas (bubbles). Not sure about dissolved gas; maybe you can tell me if that matters. Ordinary liquids (aqueous solution and biological oil). Surfactants are ...
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4 votes
0 answers
172 views

Is ozone paramagnetic?

This answer shows why ozone should be diamagnetic. Still, Wikipedia article says it is weakly paramagnetic, having positive magnetic susceptibility $χ = \pu{+6.7E−6 cm^3 mol^-1}.$ There's a paper ...
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-4 votes
2 answers
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How does part of frozen liquid ( like soup) boil and still be frozen at same time if temperature stays same while melting?

I was reading the following basic question about temperature change during phase change (During phase change in matter, why doesn't the temperature change?), and the answers provided clearly ...
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  • 647
0 votes
1 answer
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What gas particles are formed when diamond turns to gas?

If you heat up diamond away from oxygen (air completely) until the solid diamond is now gaseous, what are the gas particles made of? Just the element carbon without a charge?
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4 votes
2 answers
171 views

At constant temperature, can the solid phase be more stable than the gas if pressure decreases?

In a phase diagram, the triple point is the point at which the three phases can coexist. If we consider, for example, CO2 If we go below the triple point by decreasing pressure and keeping ...
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0 votes
0 answers
71 views

Does the 1s orbital have two different phases? [duplicate]

How can the 1s orbital (in H atom for example) interfere both constructively and destructively (to give rise to bonding and antibonding molecular orbitals) with another 1s orbital, if the 1s orbital ...
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11 votes
2 answers
149 views

Peak in beer freezing temperature plot

I left an open beer in the freezer while monitoring its temperature. The first minutes works as expected. But after the plateau, at about −8 °C, a peak appeared: I thought it was an artefact because ...
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1 vote
1 answer
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Why does boiling occur when vapor pressure equals ambient pressure?

Here is my understanding of the boiling process: pressure of the atmosphere is pressing down on the liquid and this pressure is propagated throughout the liquid. That is, pressure everywhere inside ...
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0 votes
1 answer
122 views

Boiling of ammonia water [closed]

L̶e̶t̶'̶s̶ ̶m̶a̶k̶e̶ ̶i̶t̶ ̶s̶i̶m̶p̶l̶e̶.̶ ̶I̶ ̶h̶a̶v̶e̶ ̶a̶ ̶p̶o̶o̶l̶ ̶o̶f̶ ̶a̶m̶m̶o̶n̶i̶a̶ ̶w̶a̶t̶e̶r̶,̶ ̶a̶n̶d̶ ̶w̶h̶e̶n̶ ̶I̶ ̶h̶e̶a̶t̶ ̶t̶h̶e̶ ̶a̶m̶m̶o̶n̶i̶a̶ ̶w̶a̶t̶e̶r̶,̶ ̶a̶m̶m̶o̶n̶i̶a̶ ...
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  • 19
2 votes
1 answer
45 views

Is it possible to have non metallic lithium

I have heard that hydrogen under extremely high pressure and cold temperatures can enter a metallic phase (or just ungodly amounts of pressure and high temperature) Can the inverse of this be applied ...
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1 vote
1 answer
111 views

Does the vapor pressure of a substance depend on the presence of other gases?

The Clausius-Clapeyron equation (CC equation) can be used to find the (saturated) vapor pressure of a substance ie. the gas pressure at which the two phases (vapor + liquid or vapor + solid) reach ...
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2 votes
0 answers
61 views

Raising melting point of water at STP (using disolved impurities)

Typically, water experiences melting point depression when it is impure. The more impure it is, the lower the melting point, up to a point. I understand you could raise the melting point by increasing ...
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  • 157
1 vote
1 answer
141 views

In an open system, can water vapor escape into the atmosphere before reaching the boiling point? [duplicate]

In a closed system, water vapor would have nowhere to go and atmospheric pressure would not be a factor. It would reach dynamic equilibrium with only water vapor. But in an open system, I think that ...
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2 votes
0 answers
115 views

Determining Boiling Point and Melting Point by Graph

This is the plot of $\Delta G^{^\circ}$ vs $T$ for $\ce{Pb-> PbO}$ I understand that the points where there is a sudden change in the slope of the graph, there is a phase change but exactly what ...
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3 votes
0 answers
59 views

Is there a parameter for degree of ‘mixedness’

So I was making coffee this morning and when mixing some milk into the black coffee, I wondered if there was some parameter or value in chemistry which describes how well mixed two liquids (or gases) ...
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2 votes
2 answers
101 views

Phase equilibrium & phase diagram [closed]

Q) Why does phase equilibrium/inter-conversion ONLY occur at boundary lines between phases in phase diagrams? Example: According to water phase diagram, at 200 C and 200 atm ONLY liquid water ...
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  • 29
3 votes
3 answers
271 views

What does the state of a substance at a specific T and P mean?

From the phase diagram of water, we see that water is a liquid at 20 °C, 1 atm. The state of the water at 20 °C, 1 atm is liquid. But there is actually also water vapor in equilibrium with liquid ...
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  • 169
0 votes
2 answers
133 views

Finding freezing temperature and osmotic pressure of an ethylene glycol and glycerol solution in water

A water solution is prepared by mixing $\pu{200 g}$ of a ethylene glycol (ethan-1,2-diol; $\ce{C2H6O2}$) solution (20% by weight) with $\pu{500 g}$ of glycerol (propan-1,2,3-triol; $\ce{C3H8O3}$) ...
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0 votes
1 answer
125 views

Phase of reaction between glucose and potassium cyanide to form amygdalin

I'm trying to write a detective-fiction novel, and I was wondering if potassium cyanide reacts with sugar only if the glucose for the amygdalin to form is dissolved in liquid or does it react even if ...
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0 votes
1 answer
146 views

Methanol-water mix freezing points - clarify contradictory online data > 60% w/w?

Extending an exploration of windshield washer-fluid choices to freezing points of methanol-water mixes, all web-sources located agreed to within a couple of degrees from 0-60% w/w, yet above this ...
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4 votes
3 answers
133 views

If all molecules have basically the same KE at a given temperature, why do lighter isotopes evaporate more readily?

One of the proxies used for paleoclimate is the ratio of oxygen-18 to oxygen-16 in ice cores and in sedimentary rocks. The idea is that water molecules with oxygen-18 generally evaporate less readily ...
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2 votes
2 answers
70 views

Is ionisation an equilibrium process?

I read in a page that ionisation is an irreversible process. But, as equilibrium is always reversible would that mean equilibrium does not involve ionisation process. And than dissociation is a ...
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11 votes
4 answers
2k views

Why does gas not liquify at a temperature above the critical temperature no matter how much pressure is applied on it? Why? [duplicate]

My textbook says that critical temperature is the temperature above which a gas cannot be liquified no matter how much pressure we apply on it. But why? What is so special about this 'critical ...
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0 votes
0 answers
31 views

How much energy is required to liquify oxygen?

Does anyone know where I can find some documentation of a real-world liquification process, and the energy costs? I can calculate the heat that must be removed from O2 gas to get to liquid, but how ...
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  • 197
2 votes
1 answer
50 views

Why does Sulfur dioxide incompletely freeze when entrained in a helium stream inside tubing dipped in liquid nitrogen?

Background - In a laboratory setting, I use typical elemental analysis (EA) to generate about 50 µg of sulfur in the form of sulfur dioxide (SO2). The EA uses a helium carrier. As an example, a sample ...
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4 votes
0 answers
53 views

Why is the reported melting point of formaldehyde so different from the triple point?

All of the (believable) sources at PubChem and most of the sources at NIST give 181 K for the melting point. The one source I can find for the triple point is NIST, which gives 155 K. There are two ...
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1 vote
1 answer
88 views

Can the enrichment of Uranium be done via manipulating the boiling/melting point difference between differing isotopes of the same element?

I have a Physics question for which I could not find the answer on the Internet, so I would like to see if y'all know the answer to it. I have found that heavy water will have a different boiling ...
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4 votes
1 answer
116 views

What is inside nanobubbles?

A recent article (ACS Omega 2021, 6, 8021−8027) confirms the stability of nanobubbles with theoretical principles. Nanobubbles, having a size in the range of 50-500 nm, are reported to be metastable, ...
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  • 12.6k
1 vote
2 answers
158 views

Triple Point of a compound and critical point

Is it necessary for all compounds to have a triple point? Also, how is the triple point determined? Suppose a substance does not have a triple point, so how do researchers agree on the impossibility ...
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  • 657
3 votes
0 answers
74 views

What is the difference between sublimation and instantaneous fusion+vaporisation?

Sublimation is defined by the IUPAC as The direct transition of a solid to a vapour without passing through a liquid phase. A sublimation equilibrium can occur in two sets of conditions: at a ...
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1 vote
1 answer
70 views

What pressure does liquid nitrous oxide need at −45 °C?

What pressure does liquid nitrous oxide need at −45 °C to remain liquid? How can I calculate its pressure required for other temperatures?
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  • 121
3 votes
1 answer
111 views

Depression of the Freezing Point

Recently we learnt that there is a depression in the freezing point when a non-volatile solute is added to the solvent. Our teacher explained this phenomenon with a graph where the vapour pressure of ...
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  • 31
1 vote
0 answers
66 views

Understanding Pourbaix diagram

I am recently taking courses in environmental chemistry and I was introduced to Pourbaix diagram. I was taught that the lines in the Pourbaix diagrams are equilibrium lines. Lets take as an example ...
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  • 736
0 votes
1 answer
59 views

Equilibrium for the synthesis of methanol

Liquid methanol is obtained with carbon monoxide gas and hydrogen gas in a reactor at $\pu{300 °C}$ and $\pu{250 atm}.$ $K_p = \pu{9.28E-3}.$ Find $K_c.$ With only these data, do I have to use the ...
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  • 201
1 vote
1 answer
165 views

Can vapour pressure be used to 'generate' work for free?

Given a bottle of water, a closed system, some of the water molecules in the liquid phase will have enough energy to escape that phase, forming water vapour, contributing to vapour pressure. Now ...
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  • 1,173
1 vote
0 answers
99 views

Why does vapor pressure of ice decrease faster than water when temperature decreases?

In melting point depression, I have learnt the explanation from the textbook that (e.g. aq. solution): Definition of melting point: ice and water exist in equilibrium (have the same vapor pressure). (...
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