# Tag Info

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The temperature at the boiling or condensation point remains the same for gas and liquid. 100 degrees Celsius for water at standard conditions. L called the Latent (meaning hidden) Heat of fusion times the mass of Water vapor, m, equals Q the Heat released.

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The Sun heats up the surface that it's light touches and the heat created causes the air to rise and the light hitting the hot air causes a mirage. http://en.wikipedia.org/wiki/Mirage

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The radiation of a body is given by the Stefan-Boltzmann equation: $$E= \epsilon \sigma T^4$$ Which means that if you can measure the radiated power $E$, the temperature is $$T=\sqrt[4]{\frac{E}{\epsilon \sigma}}$$ If the emissivity is lower than you think, it follows that you see less emission that you would expect for a given temperature and you would ...

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The gas gets hotter because the energy has no where to go and it must convert into heat. The molecules bounce back and forth with one another creating more and more energy and less space, so the molecules began to compress through the helical rotors.

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Instability occurring when a heavy fluid is superposed on a lighter one was first studied by Lord Rayleigh in 1883. The nature of this instability does not change when the problem is posed as a lighter fluid accelerating against a heavier one. G I Taylor first investigated it in this latter sense. The second paper in this reply will answer your question in ...

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Yes, I think they would just be horizontal lines. That's how the axes are defined. So, inside the mixed-phase region, pressure & temperature are constant.

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2nd law of thermodynamics has many almost equivalent formulations. The traditional ones always assume closed system, isolation is not needed - heat and work transfer are assumed to be allowed. One formulation: When thermodynamic system goes from equilibrium state 1 to equilibrium state 2, the entropies of these states obey the relation $$S(2) - S(1) \geq ... 1 Let us understand Brownian motion in liquids before we look at the motion in solids. If you observe a glass of water at rest on a table, it "appears" to be motionless. However, all we need is a magnifying glass to observe the random, incessant motion of water on the surface. This random motion is a manifestation of heat. The same thing happens in a solid. A ... 1 Here's a way to get a decent distance estimate for solids, liquids or gases.: for solids or liquids, you can get the number density, n, of atoms or molecules (as needed), from the density, Avogadro's number (6.02E23) and the molecular weight (\rho,N_a,W:$$n = \frac{\rho N_a}{W}$$for a gas with pressure, temperature and the boltzmann constant ... 1 If you have a path on p-V diagram that is p=F(V), then using$$ dU=\delta Q-pdV \implies \delta Q=dU+pdV $$NOTE MINUS SIGN as pdV is work done BY the system. Q is the total heat received by the system (it is negative if system releases heat). Assume we are dealing with an ideal gas with f degrees of freedom per particle (f=3 for monatomic gas). ... 1 Air pressure exists because if we place something in a gas, then the molecules/atoms flying around will keep banging into it, and in this way produce a net constant force per unit area. As explained by @Chris2807 in the neat formula P=n k_{B} T, this is proportional to how many particles there are (since this is proportional to the amount of "banging" in ... 2 When you put the pot on the stove, the heat from the stove is somehow getting to the pot, which gets hot. The pot and the stove are obviously in contact with each other. Therefore conduction plays a role here. If you have an old pot, with a warped bottom, it will heat up slower, because the contact surface between pot and stove is smaller. When you hold ... 0 By just adding on another volume (the attic space), you wouldn't really be applying Charles' Law since you've increased the amount of gas. The temperature would go down though, since you're effectively diluting the hot gas with cooler gas from the attic space. Charles's Law is simply that for a fixed mass of gas at a constant pressure, V and T are ... 1 Here's a simple mental picture to have of a how a burner on a stove heats up water in a pot (which is sitting on the burner). (In what follows, I will use the term "molecules" for both molecules and atoms.) Also, keep in mind that thermal conduction is different than electrical conduction. One (electrical conduction) concerns the flow of charge, so in this ... 4 In some sense yes. Let me explain a little. If we were to take a sealed container of gas and put it into free space far away from other bodies so that the gravitational force on the box is negligible would you agree that there would still be some pressure in the container? If we assume we have an ideal gas then the pressure is simply given by$$P=nk_{B}T$$... 3 In general, air pressure in the Earth's atmosphere is hydrostatic pressure, caused by the Earth's gravitational field. If there was no gravity then there wouldn't be any centripetal force and all the air molecules would just float away into space. This is why there is no atmosphere on the moon - because it doesn't have enough gravity to sustain one. 1 In thermodynamics, any well-behaved quantity of matter generally has a temperature (a measure of average internal energy) associated with it. Therefore, the sole addition or removal of matter from a volume is not accompanied by a change in the energy contained in that volume if and only if the matter transferred has zero temperature; transferring matter at ... 1 I was simply confused by the sign convention in the first law of thermodynamics. The most convenient way to write it is Q=\Delta U + W where W is the work done by the system. Hence the answer to my question becomes clear after this. 2 Check out the description of Charles' law on wikipedia. Charles' law relates the temperature and volume of a single body of gas at constant pressure. If you're mixing two bodies of air at different temperatures by punching a hole in the wall between them, you're not changing the volume of a body of gas at constant pressure, you're combining two bodies of ... 0 No, I don't think you have the correct entropy. I think the temperature is incorrect in the numerators, it should be (328 - 313) and (313 - 283). 1 Stoves and other hot objects heat up, but don't burn. Burning is very different. Burning is a chemical reaction. In the example of stoves, they work by conduction. 3 The thermal energy k_{B} T is really referring to the probability of finding a system in a state of energy E, given that it is in a surrounding enviroment at temperature T. This probability is proportional to e^{-E/(k_{B} T)}. Using this you can derive a great many things, including the Boltzmann/Fermi distributions. The proportionality constant is ... 5 Giving the value simply of k_B T is generally more useful, because I can plug that into anything. Sure, I might need to know the ideal gas energy, and multiply by 3/2. But maybe I need to put it into a partition function, and I just need k_B T. Maybe I'm worried about a harmonic oscillator and I just have the two degrees of freedom. The 3/2 is ... 1 Let me clear a few things up first; the latent heat of fusion is the energy required to convert a substance from solid form to a liquid form. Since water is liquid at room temperature, the latent heat of fusion is positive as energy is absorbed to convert ice to water, just as energy is released when water is converted to ice. It sounds counter-intuitive, ... 18 Mammalian sense of smell is in general exquisitely keen: even though we think of ourselves as an animal having a dull smell sense comapared to that of, say, a dog, a pig or a rat, receptors for certain scents are still triggered by molecules counted in the tens. So the outgassing of volatile wood oils from, say, a table, can still be miniscule and well ... 2 Burning the fuel in car produces less heat than just burning the fuel in an open container because in an engine some of the energy produced by combustion goes into doing work on the car. In an open container all the energy appears as heat. However the energy that goes into doing work on the car ends up as heat eventually because the car dissipates the ... 2 But if heat consists of the speed of the molecule (which is an if) then shouldn't there be an Absolute Infinity as well as an Absolute Zero? This question's "if" is not correct. Temperature (not "heat", as we use this word in a specific technical way) consists of the energy, not the speed, of particles. While these two are obviously related, it's ... 1 You state the second law as : The entropy of the universe always increases. In my college textbook it is stated as : Processes in which the entropy of an isolated system would decrease do not occur, or, in every process taking place in an isolated system, the entropy of the system either increases or remains constant.( F.W.Sears an introduction ... 0 There is a point of temperature called Planck temperature where are understanding starts to break down. Advances in quantum gravity will help us understand this incredibly high temperature and its effects on molecules. 0 When you heat up an ionic crystal, the nuclei oscillate more quickly (increase in kinetic energy) and this causes the atoms to become more spaced apart, i.e. the material expands (increase in potential energy). You can see this effect come out of the virial stress. 0 You're basically describing a car radiator. I can't see any reason why you'd need a more sophisticated heat exchanger. 0 The reason why a gas heats up when it is compressed into a smaller space, is because the ambient heat that the gas possessed in its original volume, has now been confined to a smaller volume—same amount of heat but now more concentrated—the temperature goes up. When the vessel storing the newly compressed gas cools off to the ambient temperature of its ... 0 For an ideal gas, we neglect all intermolecular interactions (except for the trivial case of elastic collisions). \Delta U therefore depends purely on the kinetic energies of the particles. The 'decreasing of intermolecular distances' has no role to play here. However, these things are taken care of to some extent by the van der Waals equation Melting is ... 0 If you compress an ideal gas adiabatically, the average kinetic energy of the particles will increase because collisions with the moving piston will increase the kinetic energy of the colliding particle. For an ideal gas, the intermolecular distances have no bearing on the internal energy. More specifically, suppose the piston is moving inwards at velocity ... 2 It would certainly require a material that allows electron release from energies lower than those of the visible spectrum. The energy of a wave is given by E=hf where h is the planck constant (6.63 x 10^-34) and f is the frequency. The wavelengths of IR light range from 0.001 m to 750 x 10^-9 m. (Hyperphysics.com, infrared) Using this knowledge you can get ... 2 Q = mc(t1-t2), Now, m = (density)(volume), Specific heat of water, c(in joule/gramCelsius) = 4.186, Hence, you can find the energy it would require for this conversion. . And the work you do can be a bit more pertaining to your efficiency. 0 You asked: "Does one imply another?" No. Neither implies the other. However, I think there are benefits to first being clear what the ideas are, particularly since I think each idea actually already assumes an arrow of time. In the first case, you start with an arrow of time that only earlier times affect later times, and then end up strengthening that to ... 2 You are sloppy with units, but the result is correct. To go from 25C to 3C is 22 cal/g. When you multiply by 300 g you have cal and your conversion to kJ is correct. Converting to W-hr is silly, but that is the unit of energy, not W/hr. You have 8.3 W-hr you want to remove. That chills the water assuming no new heat is added, so insulate the water. ... 1 This might be better on the engineering SE site but here is some physics to consider: You are right the the heat you need to remove is the mass of water times the temperature difference times the specific heat capacity. Peltier devices and other heat pumps typically have a parameter called a COP - coefficient of performance. This compares their efficiency ... 0 There is a simple way of looking at this. Would a container of gas have a change in temperature if the container was given a different velocity? For your second question, the vibrating membrane acts like a spring pendulum which transfers energy into the surroundings. The membrane does not have a change in temperature until it absorbs the energy back from ... 1 Water forms close to perfect spheres in zero gravity due to it's surface tension. There's a variety of videos of water in the space station. Ice, assuming you start with one of those balls of water, you have to ask first, would it freeze outside in (say, the temperature of the station is dropped below 0 C), or would it freeze inside-out, say you stick a ... 0 Sound will behave just like on earth provided it has a medium to travel through (Astronauts on the ISS can communicate normally; watch some videos) 0 In first place, the temperature is a quantity that measure thermal equilibrium by the zeroth law of thermodynamics. We have the contact with this quantity by with a thermal equilibrium can do. For example, the Celsius units is constructed by define 0°C as the volume of mercury in contact with freezing water and 100 °C as the volume of mercury in contact ... 0 Since both are at the same temperature, both have the same degree of hotness ie. Temperature, hence similarly cold or hot. The difference is that water and ice both have different enthalpies, Water when converted to ice requires only phase change enthaply(assuming water to be at 273K), the enthalpy of freezing is then, Q(f) = ml 0 First law of thermodynamics is the extension of Law of Conservation of Energy for non-isolated system. There are two forms of first law of thermodynamics(both are actually same): Followed by physicists best suited for dealing with heat-engines:$$\partial E = \partial q - \partial w$$. Here \partial w is the work done by the system. Followed by chemists ... 2 Consider a container containing n moles of an ideal gas. The gas exerts a pressure P on the container and the piston. If P equals the atmospheric pressure, then the piston does not move, as it experiences equal forces from in and out of the container. When you increase the external pressure, the gas in the container is compressed. If the compression of the ... 0 Can anyone help with this derivation? There are N! ways to arrange N different objects, but you don't have N different objects, you have n_0 indistinguishable objects in the ground state, n_1 indistinguishable objects in the first state, and so on. So that means, from your N! different permutations (assuming all the objects are ... -1 Amps travel in a straight line and so must travel inside the wire. Volts travel around the amps and usually outside the wire. So amps will generate heat - because of the atoms and valence electrons create degrees of resistance - while volts , generally, will not. But if you use thick enough wire you will not notice the heat increase. 2 The one that absorbs more heat from you will cool you more, and seem colder. But it isn't entirely straightforward. If you pour water in your hand, water will flow to fit you. An ice cube will not make as good contact. Water in contact with you will warm. It can then flow away and be replaced by fresh cold water. Ice doesn't flow On the other hand, Ice ... 3 The filament will be a reasonable approximation to a black body emitter, so it's spectrum will be given by Planck's law:$$ B = \frac{2hc^2}{\lambda^5} \frac{1}{e^{\frac{hc}{k\lambda T}} - 1}  So just measure the radiance of the light from the filament for a range of wavelengths and do a fit to Planck's law by varying $T$. This will give you an excellent ...

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