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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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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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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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
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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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58 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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Why is it important not to use the Clausius-Clapeyron equation for the transition from solid to liquid

I have to comment the following quote: It is important not to use the Clausius-Clapeyron equation for the transition from solid to liquid My professor hasn't yet introduced this yet, but if you have ...
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1answer
51 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
44 views

Depression of FreezingPoint

Recently we learnt that there is a depression in freezing point when a non volatile solute is added to the solvent. Our teacher explained this phenomenon with a graph where the vapor pressure of the ...
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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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51 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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158 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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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
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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
492 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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1answer
65 views

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
34 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
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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
47 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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Is it possible to have three stable liquid phases in a binary mixture?

With this system, it would be possible to have three liquid phases and two liquid-liquid coexistence regions at various compositions. Similar behaviour is common for solids such as alloys, sometimes ...
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ethanol/water %vol/vol and freezing temperature

Main Question: Where can I find a table (or realistic formula) for isopropanol/water %vol/vol mixes and corresponding freezing temperature with public access? Background: Trying to get the freezing ...
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Carbon properties [duplicate]

Can carbon in the form of graphite melt or even boil? Under what experimental conditions? I ask this question because I found in a very serious book (Tables CRM Commission romande de chimie) ...
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1answer
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Is there an actual specific heat for aluminum in its gaseous state? [closed]

I've scourged the internet and I can't seem to find it anywhere although I've found the specific heat values for aluminum in both solid and liquid states. I'm trying to construct a heating curve and I ...
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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 ...
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115 views

Partial molar volume of binary mixture

A 2% (weight %) solution of a salt with Mr = 190.6 g mol-1 was prepared at 25 0C. The density of the prepared solution was 1.00926 g cm-3. The density of water at 25 0C is 0.99707 g cm-3, and the ...
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1answer
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Does helium freeze at absolute zero? [duplicate]

Does helium freeze at absolute zero? In theory, it should, since all random motions of particles stops at absolute zero, right?
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Is it easier to mix a solution that is in the liquid or in the vapor phase?

In the article on dilution, Wikipedia has the following statement: The same direct relationship applies to gases and vapors diluted in air for example. Although, thorough mixing of gases and vapors ...
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The formation of ice crystals on/in frozen food that has been defrosted and then frozen again

I made a mistake. I put my ice cream in the refrigerator instead of the freezer and left it there for a night. I realized my folly the next day. I put it in the freezer. When I took it out, I noticed ...
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Why does diethylmethylamine have such a low melting point?

According to PubChem, diethylmethylamine has a remarkably low melting point of $-196.0\ \mathrm{^\circ C}$. This is substantially lower than the melting points of dimethylethylamine ($-140.0\ \mathrm{^...
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Working out energies of hydrogen bonds by comparing chemical potential of vapour and condensed phase - equation derivation

I want to ask a question about working out the energy of a hydrogen bond between two water molecules, $w_{AA}$ using the chemical potentials of vapour and condensed phases. I was reading K. Dill, ...
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At what pressure will hydrogen start to liquefy at room temperature?

I want to increase a fixed-size object's internal gas pressure by generating hydrogen in it, but I could not find the proper phase diagram for it. So I am wondering how high pressures I can get.
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1answer
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Why is change in internal energy not equal to zero during a phase transition? [closed]

Many books state that when there is no change in temperature $\Delta U$ is equal to zero. Why is this not applicable for phase transitions? I have had this question for a while now and have been ...
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297 views

Why is the temperature graph sigmoidal in simple distillation of components with very different bps?

I'm writing an organic chemistry lab report on distillation and I thought I understood this, but the more I look at my lab textbook, I realize I don't. My textbook 1 explains that the temperature of ...
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1answer
56 views

Brittleness of Ice?

I am curious as that I know that various materials can be subjected to fragility from ductile-brittle transition via temperature, where an item is more likely to fracture of shatter such as increase ...
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1answer
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Formulations for wax thermostatic element for effect in alternative temperature range

Wax thermostatic elements are used automobile cooling systems and anti-scald mixing valves to control flow rates or to adjust mixing of flow inputs. These devices operate on the principle of thermal ...
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Does fractionation use enough heat to destroy nutrients in Coconut Oils when seperating the MCT oils?

We have recently been giving MCT (medium-chain triglyceride) oil to our dogs in place of Coconut Oil as from what I understand the majority of the benefits of Coconut Oil comes from the MCT's ...
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1answer
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Place cooling bath apparatus in freezer to speed up the process?

As part of an at-home lab, my chemistry class is creating cooling baths to measure the freezing point of different solutions. We have to determine the molar mass of the solutes in these solutions by ...
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148 views

Does the temperature during ice melting change? [duplicate]

I did an online test for physics and one of the questions was: Salt was added to ice. Because of it the ice melted. What was happening with temperature DURING the process of melting? The right ...
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105 views

Freezing point of solution of Water, Ethanol and Sugar (aka, Limoncello)

I'm looking for a diagram of the freezing point of a water solution depending on its content in sugar and ethanol. More colloquially, I want to know how to balance alcohol and sugar so that my ...
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1answer
89 views

Predicting sign of enthalpy of allotropic transition of phosphorus

How to predict the sign of enthalpy during the transition $$\ce{P(s, white) -> P(s, red)}?$$ $\ce{P(s, red)}$ is more stable than $\ce{P(s, white)}$ due to release in angle strain. Since during ...
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264 views

Latent heat of vaporization/evaporation

It's the amount of heat required for liquid ---> gas phase change of a substance at it's Boiling point. But my question is, does providing energy equivalent to latent heat of vaporization to a ...
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2answers
239 views

Internal energy for Phase Transitions

Can we justify that "For sublimation of a solid at 1 atm $\Delta U>0$ at low temperature and $\Delta U<0$ at high temperature?" I read several answers and came to know that $U=f(T)$ ...
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Why is the molar entropy of hexane lower than that of butane?

Entropy is dependent on the complexity of the molecule. Due to this, I expected entropy to increase as the complexity of the molecule increased. According to p 918 of Atkins' Physical Chemistry (9th ...
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74 views

Molality of solution to be used when finding water separated from solution as ice

Question $\pu{1 kg}$ of a solution of cane sugar is cooled and maintained at $\pu{-4 ^\circ C}$. How much ice will separate out if molality of solution is $0.75$? $K_\mathrm{f} \ \text{(water)} = 1....
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1answer
50 views

What is happening at the various boundaries of a phase diagram? [closed]

Hoping to clarify a few questions I have that the textbook doesn't address. Lets just say I have a piston (at equilibrium) with 100 moles of gaseous compound that looks like this: And here is the ...
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Aluminium oxide phase diagram

I have been looking for the phase diagram of alumina or Aluminium oxide, could it be that there is not something like that? thank you

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