# Tag Info

18

Vapor is a much older word alluding to dampness and it was not coined by scientists. It is in use since the 1300s. The actual meaning of meaning of vapor is "Matter in the form of a steamy or imperceptible exhalation; esp. the form into which liquids are naturally converted by the action of a sufficient degree of heat. This is the original 13th century ...

14

The normal use distinguishes "vapour" from permanent gas At normal lab conditions there is a (fairly obvious) distinction between things that could exist as liquids and things where no liquid phase is possible. Oxygen, for example, is a permanent gas, but dichloromethane is not. But the vapour pressure of dichloromethane is pretty high and there ...

10

I don't know if there would actually be oxygen and nitrogen snow. I would think under those circumstances, there might be carbon dioxide snow, but the rest of the atmosphere would probably liquify first, there may be oxygen and nitrogen rain with some hail or sleet, but snow? Not sure it would happen. If it did, oxygen and nitrogen snow would be different ...

10

I'm surprised the OED has such a strict definition for gas. I could not find a strict definition in the IUPAC color books (certainly not in the gold book). Presumably these words are in such common use that their definition is assumed understood or easily found. The analytical compendium (orange book) and physical chemistry book (green book) mention vapour (...

9

There is one importing principle to consider. Air does not store vapor. Space does. Less space means less vapor capacity, no matter how much of air is there. (*) If air is being compressed, the partial vapor pressure increases. It it reaches the saturated vapor pressure at given temperature, water vapor starts to condensate. When air is then expanded, its ...

6

In college, I had a thermodynamics teacher who was awesome. He had a way of explaining things that were accurate and easy to understand. He explained this difference to us this way: A gas will not condense into a liquid with an isothermal compression. (i.e. an Ideal Gas) A vapor will form liquid when isothermally compressed. His example: When you boil water, ...

6

tl;dr– "Gas" and "vapor" aren't mutually exclusive. Generally: a gas is any material that'd fill a volume to its boundaries; and a vapor is a gas-like material that's associated with a condensed-state transition. It's a bit misleading for a state-diagram to label a region "vapor" in a manner that might imply that a vapor's ...

3

Using NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) – NIST Standard Reference Database 23, Version 9, I found the saturation point of nitrous oxide at equilibrium for a temperature of $T=-45.000\ \mathrm{^\circ C}$ at a pressure of $p=783110\ \mathrm{Pa}=7.8311\ \mathrm{bar}$; for $T=-78.000\ \mathrm{^\circ C}$, it is $p=... 3 The background of the topic is, that for the function $$y = \frac {a(T)}{x}$$$y$does depend on$T$, but$x$does not.$\mathrm{pH}$of basic solutions is temperature dependent via$\mathrm{p}K_\mathrm{w}$temperature dependance. Additionally,$\mathrm{pH}$of weak acid/base solutions is temperature dependent via$\mathrm{p}K_\mathrm{a}$or$\mathrm{p}K_\...

3

To succinctly answer your question, yes. However, they are not epoxies, and typically not available to a hobby enthusiast. There is no such thing as a high temperature epoxy. The maximum service temperature of epoxies is around 200 C on a good day. Higher temperature resin systems for 250 a 300 C are typically BMI-resins. These are rigid, thermoset ...

3

You're really asking about the difference between a physical change and a chemical change.* In a physical change, the chemical identity of the substance doesn't change. In a chemical change, it does. Suppose you take cube of sucrose (table sugar) at room temperature. If you heat it up, it will become warmer. But it will still be, chemically, sucrose. It ...

2

Fire or flame is a luminous chemical reaction in the gas phase, i.e, such a chemical reaction is generating heat + light. Not all flames are very luminous e.g., hydrogen oxygen flame is very very light blue...hard to see. Candle flames are yellow because of glowing carbon particles. The blue/purple color comes from small molecules formed by the decomposition ...

2

Your major confusion may be thinking intensive property must be property of material. There are 3 types of quantities, depending how they are related to system scalability: Extensive properties are additive wrt(with respect to) the system scaling. If there is twice as big system, there is twice as big value of an extensive property. Examples are mass, ...

2

Temperature will increase. If system is adiabatic, it doesn't neccesarily mean that temperature of the system can't change because even though system can't exchange energy with surroundings, processes inside can generate heat. In your example, exothermic reaction. Note that, internal energy in your case stays the same even though temperature increased. This ...

1

Accuracy and precision are determined by the quality of the measurement, not the units used. The units themselves don't limit accuracy or precision, since the measurement can be expressed to whatever number of significant figures are needed, e.g., $\pu{35.4848923 ^{\circ}C}$. As another example, grams are not more accurate or precise than kilograms. If you ...

1

Celsius. The preciseness of the scales are the same. Numbers are numbers. However, upon comparing the methods for obtaining the values, a judgement can be made. Fahrenheit was initially set to zero with the eutectic temperature of a solution of a brine, a mixture of water and ammonium chloride in which water ice forms and is present. The secondary point, by ...

1

@aNoNyMoUs When you say "the solubility of a solid only decreases with the temperature", it is only true for solution of pure compounds. It is not valid for solutions containing more than one compound. For such mixtures, specially if the solutes have a common ion, a different calculation must be done. The solubility has to be calculated by the ...

1

Assuming you want to generate vapors of iodine at ambient pressure, you need to surpass its boiling temperature. Wikipedia's box about iodine's physical properties state about $\pu{184 °C}$ for this phase transition ​(about $\pu{364 °F}$). You intend to use a barrel made of high density polyethylene, HDPE. Wikipedia's entry for a typical specimen of HDPE ...

1

The acoustic wave is accompanied by a temperature oscillation. To a first approximation, the temperature oscillation is adiabatic and reversible in the bulk, but irreversible near solid boundaries. In many cases, boundary losses dominate (for example, in musical wind instruments), but as the frequency increases, and the surface-to-volume ratio decreases, ...

1

You're using the wrong value for the specific heat of water, because we're dealing with kilograms and joules here, and not calories and grams. It should be: $$4184\ {\rm J\over kg\cdot\ ^{\circ}C}$$ and the minus sign goes away because the heat that is lost by the metal is gained by the water, hence $\Delta Q_\text{water} = -\Delta Q_\text{metal}$. Thus, we ...

1

The principle of calorimetry states that in an isolated system such as a calorimeter, the total heat gained by the colder bodies is equal to the total heat lost by the hotter bodies. So since we are calculating heat lost by metal, you should take $$\Delta T = \pu{50 ^\circ C} - \pu{20.64 ^\circ C}$$ What's more, the specific heat of water is $\pu{1 cal g-1 ^\... 1 The easiest way to prove the equality in pressure is by taking a cross-section of the narrow tube and finding the forces acting on it. By extending this, we can prove that the pressures are equal. Take a cross-section area of the narrow tube. We assume this is at steady state and there is no average motion of particles in the entire system. Now, since there ... 1 Vapor (or steam for H2O) can be used for the gaseous form of a particular substance which at normal T and P are solid or liquid. They are all gases although not always ideal (steam is certainly not ideal below its critical T). 1 In a real gas, the internal energy is the sum of the kinetic energy of the molecules and their potential energy of interaction. An ideal gas is the limit of real gas behavior in the limit of large molar volumes in which the potential energy of interaction of the molecules approaches zero. The kinetic energy of the molecules depends only on temperature, but ... 1 The impact temperature has on the pKa of strong acids are in practical terms non existent as the equilibrium at any temperature lays very far to the right. Practically, yes. The impact of temperature on pKa are more significant for weaker acids. Yes. The impact of temperature on pKw is only significant around the point of neutrality. At lower pH's the ... 1 Why does a solution become less temperature dependent the more acidic it is? Basic solutions are extremely temperature sensitive, neutral solution still significant sensitive, but highly acidic solutions don't seem give a damn about temperature. Why is that? Is this statement based on theory or on your own experience? It is my understanding that pKw is ... 1 Well, it works both ways... t[deg C] pKw Solution pH pOH 25 14 0.1 M HCl 1 13 25 14 0.1 M NaOH 13 1 50 13.27 0.1 M HCl 1 12.27 50 13.27 0.1 M NaOH 12.27 1 1 Total entropy and Gibbs energy: An alternative view on the Gibbs energy may help to get some insight: $$\Delta S_{sys} + \Delta S_{surr} = \Delta S_{tot} = -\frac{\Delta G}{T}$$ The second law of thermodynamics tells us that a process is spontaneous only if the total entropy$S_{tot}$does not decrease. The sign of$\Delta G$tells us whether$S_{tot}\$ ...

1

You can use fireplace sealant which can withstand 1500 °C to substitute the resin. This method works with carbon fiber but I don't know about fiberglass. Credits: amazingdiyprojects, Integza (he build a pulsejet out of this material)

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