# Tag Info

0

My quick read of a few articles on Q, the reaction quotient, suggest that it's generally rather small. Thus $ln(Q)$ is negative, so $- T * ln(Q)$ is positive and the potential difference increases with temperature.

3

The light that we see coming from the Sun is mainly due to black body radiation at its surface. The spectrum of black body radiation is statistical in origin, and as long as there are enough processes contributing to it the black body spectrum is independant of the microscopic details and depends only on the temperature. There is a discussion of this in the ...

0

An important note to the other answers so far: the actual mass of a single particle (the rest mass as it used to be commonly referred to) does not change if the temperature rises (by temperature I mean that of the environment since temperature is a macroscopic quantity). The (rest) mass of a particle is the $m$ in $$E = \sqrt{|\mathbf{p}|^2c^2+m^2c^4}.$$ ...

-1

photon has very light mass almost negligible amount, so temperature does not effect mass of the object, but you take large object with high temperature it indicates measurable amount of mass change. example sun.

1

The Verdet constant is a coefficient which sums up the magneto-optical properties of the medium. So, the temperature and wavelength dependence are wrapped up in it. Fundamentals of Photonics by B.E.A. Saleh expresses the Verdet constant in terms of the wavelength as $$V\simeq-\frac{\pi\gamma}{\lambda n}$$ where $\lambda$ is the wavelength of the light ...

1

I believe the 'urban legend' you are referring to is about cooling a bottle when you do not have a refrigerator. On a hot and windy day you could store your bottle in the sunlight, but it would be better in the shade, but if you really wanted to cool the bottle by a few more degrees, the 'myth' says wrap it in wet paper or cloth. During the time when the ...

2

It may actually work, as evaporating liquids need heat to evaporate, and water will somewhat evaporate even in the fridge. I am not sure it works in practice, because the paper also causes an adverse effect, it provides insulation, Hard to tell which effect is dominant. I'm pretty sure that the balance of both effects depends in a very large part on the ...

2

Yes - you can have a state where increasing the pressure would create a supercritical fluid See Phase Diagram

0

The relation between energy and temperature is $$E = k T$$ with possibly something like $\frac{3}{2}$ in front, depending on the atoms or molecules we are talking about. Plugging in the numbers, we get $2.68 \cdot 10^{9} K = 2.68 \cdot 10^{9} C$ (no conversion needed for an approximation, as $10^9 - 273 \simeq 10^9$) Why some cases you get ...

0

Most campuses have a ceramics section to the art department. Gas and electric kilns are great for this. At the temperatures called "cone 9" and "cone 10" everything inside the kiln becomes invisible. It is just red-orange inside. The light bulb is a terrible example. The filament in an insulating chamber with a tiny hole is OK as long as the whole chamber ...

0

let's say the trace is the expectation value. the action will be invariant so by calculating the expectation value of the action one would expect a minima on the path taken by a particle. This would be independent of time, the same physics will describe the dynamics tomorrow. hence, periodicity in the temporal direction is a way of saying that if something ...

2

See this explanation from here: Right at the heart of the Earth is a solid inner core, two thirds of the size of the Moon and composed primarily of iron. At a hellish 5,700°C, this iron is as hot as the Sun’s surface, but the crushing pressure caused by gravity prevents it from becoming liquid. Surrounding this is the outer core, a 2,000 km thick layer of ...

2

The boiling temperature of a liquid is not the temperature at which it can enter the gaseous state. Rather, it is the temperature at which the saturation vapor pressure $e_s$ is equal to ambient atmospheric pressure. This is why, for example, water boils at lower temperatures at higher altitudes. Furthermore, water is always evaporating. It is also ...

0

All water moleucles contain energy, in accordance with the temperature. Hot water has enough energy to escape the liquid as vapour. Even though a body of water is below boiling point, the molecules with more energy (relative to the body of water),rise to the top and can escape, as vapour Tis easy!

-1

In Science class, my teacher put a flask of water on his worktable, covered it with a glass dome with a rubber rim on it so as to seal the dome to the desk. He then hooked a hose to the dome, the other end to a vacuum device and proceeded to remove the air from the dome creating a very low pressure zone within the dome... as the pressure dropped, the water ...

3

Imagine spinning a roulette wheel, but instead of dropping in one ball, you drop in 100. They all rattle around at different speeds, like the molecules in water. You can cool them down by spinning the wheel slower, so they bounce about less; heat them up by spinning faster so they bounce more; you can freeze them by stopping the wheel and waiting till ...

0

These answers account for the kinetics of the process. Thermodynamics provides an alternate picture, well suited for any question involving phase transitions. For the system of liquid plus empty volume, the free energy can be lowered by trading some enthalpy (to take molecules from the liquid into the gas phase) for the increase in entropy (all the states ...

6

Temperature is a measure for how much kinetic energy the molecules in a substance have. If the temperature is high, they are moving pretty fast, if the temperature is low, they are moving a lot slower. If molecules are moving slow, they bundle up and you get a solid. Once you heat it up a bit, the substance starts to become liquid. When you heat it up even ...

0

It can also be understud by the idea of partial pressure. Water will evaporate in an atmosphere until its partial pressure has reached the vapour pressure given for the ambient temperarture (relative humidity of 100%).

1

At the boiling point the gas is produced inside the liquid, but at the surface you constantly have molecules going in and out. If the environment is kept quite dry, then few molecules will come back in with respect to the ones that leave. Off course the higher the temperature, the easier will be for a molecule to get enough energy to break free, but this can ...

36

Think of temperature as average kinetic energy of the water molecules. While the average molecule doesn't have enough energy to break the inter-molecular bonds, a non-average molecule does. Water is a liquid because the dipole attraction between polar water molecules makes them stick together. At standard atmospheric pressure (acting somewhat like a vice), ...

0

Think of it as a resistors in parallel problem. You have a heat source inside the room and a constant temperature outside (if you assume that the outdoors is infinite and well connected to the walls. Then you have a thermal resistance/area for the wall, ceiling and floor material. Using the total area you have an overall thermal resistance and a ...

0

It is correct to say that a thermometer cannot measure the temperature of an object accurately.You must reflect deeply on the fact that all the laws and measurements that we have in physics are some sort of approximations .Since matter is made of elementary particles this distinction of thermometer and the body whose temperature is to be measured are itself ...

4

Modern processors are built from CMOS technology. These digital circuits consume relatively little current when sitting in one state or the other. However, there is some inevitable capacitance on every node. When the output of a digital gate changes state, that capacitance is charged or discharged, which means current has to flow. The total average ...

2

Assuming the total heating power entering the system will be constant, the only factor to minimise is the wasted heat leaving by air convection and radiation. To minimise that, you want to keep the pot as cold as long as possible, because all such heat transfer mechanisms are vastly more efficient when the temperature difference (as well as absolute ...

0

Heating up some mass to a certain temperature requires a certain amount of energy no matter how you heat is up. However heat transfer between your hotplate and your pot depends on the temprerature gradient (temperature difference), as well as the efficiency of the heating process. So if you boil your water in smaller protions you work with smaller ...

0

The energy it takes to boil the water is independent of the process: it is equal to the difference in enthalpy between liquid water at 15c and boiling water (assumed to be saturated liquid). To go further you need to make assumptions regarding the heat losses.

1

If you have forced heat flow by lets say an electric stove the temperature increases linearly with time and both ways should take the same time and also same energy (constant power, no heat losses on stove and pot assumed). If heat transfer is driven by temperature difference as with a gas stove ($T(t)= T_{15}+(T_{100}-T_{15})(1-e^{-\frac{k A }{m c_p}t})$, ...

1

I think that you can state that it can not measure the temperature of a substance before it have been test but it can measure the temperature after it have come in equilibrium with the substance. For example, in an experiment that need to push a liquid to T temperature, what you do is heat up the liquid with the thermometer already inside. With this you ...

2

Your description of the disturbance wrought on the system by the thermometer is sound. You may be able lessen the effect with a thermal diffusion model of the thermometer and by calculating what the system's temperature was before it brought the thermometer into equilibrium with itself, but for that approach to work, one must know the system's heat capacity ...

-1

yes, it can, because you can adjust for the mentioned effects, at least in theory.

0

The main problem with your idea is that 'whatever is required' contains data that CANNOT be determined sufficiently due to the uncertainty principle. Funnily, the same thing that would make computation on particle level terribly complex due to the large number of particles involved, works in favor of the statistical approach that is compatible with said ...

2

The velocity distribution is related to the temperature by the Maxwell-Boltzmann distribution. You cannot find the disordered kinetic energy of each particle because they are randomly distributed, however you can use the Maxwell-Boltzmann distribution to calculate what that random distribution looks like.

1

You are absolutely right that the limit in which this approximation holds is $$\beta(\epsilon - \mu) \gg 1 \,,$$ which is not trivially the 'high-temperature limit', and indeed looks rather like the low temperature limit. However, it also looks like the limit of large negative $\mu$. If we want to know how temperature will affect the exponent, we need to ...

2

George Goble won the 1996 Ig Nobel Prize in Chemistry by pouring liquid oxygen on a barbeque containing unlit charcoal briquettes and a smoldering cigarette. It did not put out the cigarette. It melted the barbeque. If he had soaked the briquettes in liquid oxygen first, it would have been the equivalent of lighting the barbeque with sticks of dynamite. ...

4

Just for completeness, when a gas expands its temperature does not necessarily change. The temperature of the gas only changes if it does work on something, for example its container as discussed in Danu's answer. If a gas is expanding into a vacuum it does no work and (to a first approximation) its temperature does not change. This type of expansion is ...

2

Consider a gas in a container. When the container expands, the gas cools down. The crux is in thinking about why the container expands. The reason the container expands is because there are gas particles hitting the walls, pushing them outward: they do work on the walls! This work on the walls costs them some energy, so that they now have less kinetic ...

2

Enthalpy (H) is the internal energy (U) of a material PLUS the product of pressure (P) and volume (V). $H = U + PV$ by definition When something boils, the gas phase takes up more volume than the liquid phase. So unless the boiling is in a vacuum, work is being done by expanding against a pressure, such as atmospheric pressure. This represents a change in ...

Top 50 recent answers are included