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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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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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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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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What state of matter do you find in a gas beyond the "dome" of its PV isotherm graph?

My book says that beyond the shaded dome region of a gas' PV isotherm graph, there is no difference between the gaseous and liquid state, and it's just a dense fluid. Why is this so? What is special ...
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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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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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2answers
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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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The mechanism of discoloration due to changes in the state of CP

I don't know the mechanism of discoloration due to phase change. https://pubs.rsc.org/en/content/articlelanding/2019/cc/c9cc02172h In the above paper, Cu(I) in CP1 (Figure 1 a) has a tetrahedral ...
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1answer
37 views

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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1answer
129 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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53 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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131 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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1answer
71 views

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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1answer
49 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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1answer
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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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1answer
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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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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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1answer
111 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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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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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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2answers
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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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3answers
259 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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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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1answer
74 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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1answer
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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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3answers
108 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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2answers
68 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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4answers
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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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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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1answer
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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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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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1answer
76 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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1answer
111 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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2answers
117 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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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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1answer
61 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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1answer
81 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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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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1answer
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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1answer
164 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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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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1answer
63 views

Freezing point depression and organic molecules

Do organic molecules reduce the freezing point of water in the same way that inorganic salts do? I've recently been swimming in lakes with a high organic content (e.g. mostly tannins. There's a lake ...
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1answer
45 views

Chromatography- why tM is separated from other peaks? [closed]

tM in Chromatography is the time of exist mobile phase. But, the mobile phase exist together with all the compunds that tasted in the process. So, why in the graph of signal to time we can see a peak ...
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3answers
537 views

What does heterogeneous mean?

We say that a homogeneous sample consists of the chemically same type of molecules whereas heterogeneous ones vary chemically, i.e. the molecules throughout are not same and also not uniform. Why do ...
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Does water have properties suggesting it has a phase transition at 50-63 Celsius so it has two phases?

https://www.youtube.com/watch?v=YsQXN-Kh2-w&t=497s In this video, he says that water has four properties (surface tension, refractive index... ) that transition from 50 - 63 Celsius between ...
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2answers
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What is the phase of matter that has flexible volume, but constant shape?

In this YouTube video it argued that: Solids have constant volume, and constant shape Liquids have constant volume, but flexible shape Gases have flexible volume, and flexible shape (in fact they don'...
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1answer
94 views

Definition of enthalpy of vaporization

The amount of heat required to vapourize one mole of a liquid at constant temperature and under standard pressure (1 bar) is called its standard enthalpy of vapourization. The enthalpy of vaporization ...
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1answer
211 views

Comparison of evaporation rate of liquids

Evaporation: Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. When a molecule near the surface absorbs enough energy to overcome the ...
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1answer
118 views

Phase rule for a pure substance in vapor-liquid region

I'm confused with how the Gibbs Phase Rule works for pure substances in liquid-vapor mixtures. According to the phase rule, there should only be one degree of freedom for a two-phase mixture with a ...
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Why does a spur of ice sometimes appear when freezing water in my freezer

From time to time, a long spur of ice grows on one “cube” of my ice cube tray. It’s quite slender, about 3mm or 1/8 inch at the base tapering to about 1mm at the tip, but it’s about 30mm or over 1 ...

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