Questions tagged [heat]

For questions about heat - a form of transfer of energy from one body to another or from one body to its surroundings. Also see these tags: [thermodynamics], [enthalpy], [energy], [temperature].

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Is the heat (or work) of the system always equal and opposite to that of the surroundings?

I know energy must always be conserved by the first law of thermodynamics, but is there ever a scenario in which a system say releases some amount of energy as work, and the surroundings gains equal ...
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example of endothermic luminescence?

Someone posed an interesting question to me the other day: is all production of light accompanied by the generation of heat? I have found that the question as posed invites vague answers, so I thought ...
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Enthalpy/Temperature change in a chemical reaction

I was wondering how exactly absolute temperature change in a chemical reaction could be calculated. For example, consider this reaction: 3H₂+N₂→2NH₃, ΔH=-46kJ/mol (298.15K) Assuming the given reaction ...
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Heat of Sublimation of GaAs and SiC

I am trying to find values for the heat of sublimation of GaAs and SiC, but can't find anything. I also tried searching for the heat of fusion and vaporization, to calculate the heat of sublimation ...
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Dry ice sublimation rate in water

As I got some a finger sized of dry ice in water, it started to bubble vigorously as expected and gave off a lot of smoke. But after 3 minutes or so, the rate of sublimation seems to slow down a lot, ...
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What would happen if I increase the pressure and temperature of a gas present in a container

Assume the gas to be a real gas and the container to be made of diamond or anything stronger than that. Take the amount of gas to be 2mL and the pressure is increased with the help of strongest ...
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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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Why is the enthalpy change of an ideal gas a function only of temperature?

While teaching us thermodynamics our chemistry teacher told us that enthalpy change of a real gas is a function of temperature, pressure etc. but the enthalpy change of an ideal gas is only a function ...
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What can happen to overheated aluminum cookware?

I accidentally overheated an aluminum espresso maker, to around 250-300° C in my estimation, but it might be even higher - I didn't measure, though. After research, I found that the material used is ...
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Double boiler apparatus with no loss of water?

Is there an apparatus that operates like a double boiler, but loses no steam? In other words, in a normal double boiler the steam is allowed to escape, so energy is lost and the boiling pot must be ...
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How to thermally insulate beaker glass on hotplate?

I bought a magnetic stirrer with a hot plate almost identical to this one. I am trying an experiment where I need to heat the beaker/mixture to about 100 degrees C. However the mixture/beaker is ...
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189 views

Is it possible to increase the internal energy of an ideal gas in an isothermal process?

Ideal gas is the one in which there are no attractive or repulsive forces acting and hence its internal energy is due to kinetic energy of its molecules. We may then say, for an ideal gas internal ...
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Constraints on pyrotechnic explosives that won't detonate spontaneously at 500 °C when landing on Venus?

The Space Exploration SE question Premature detonation of explosive bolts when landing on hot Venus? explains the need for and widespread use of pyrotechnic fasteners and cable cutters for Mars ...
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Heat released at constant pressure and temperature and heat released at constant density and temperature

Is there a relation between heat released at constant pressure and temperature and heat released at constant density and temperature? I was reading some books on propulsion and combustion, and the ...
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Entropy change during electrolysis of water

Consider the electrolysis of water reaction: $$\ce{H_2O -> H_2 + 1/2O_2}$$ At room temperature and atmospheric pressure, the change in enthalpy of this reaction is $\Delta H = \pu{+286 kJ mol-1}$. ...
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Calculate Specific Heat given initial temp, final temp and equilibrium temp [closed]

I would appreciate if someone could enlighten me on this question. Question: A metallic object with a mass of 2 kg at 50ºC is placed in 10 L of water at 20ºC. When the thermal equilibrium the ...
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How does the surface to volume ratio of ions and their distribution in solution compare to that of suspended nanoparticles in nanofluids?

I am interested in understanding the heat transfer capabilities of fluids. Nano-fluids are suspensions of nanoparticles (1-100nm sized particles) in a base fluid, often water, oil or glycol. These ...
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375 views

A possible reaction of heating Terephthalic acid

There is no reaction of terephthalic acid heating effect on the internet (at least Wikipedia). I have written the most probable reaction possible as per my knowledge. Please tell if it is spontaneous ...
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Change in Enthalpy when Pressure is constant

Okay so let me start from the beginning. I know that $ΔH= ΔU + p ΔV$ ( at constant pressure). Expanding $ΔU$, $$ΔH= q + pΔV + pΔV ~~~~~\text{(q at constant pressure)} \tag{1}$$ Next my chemistry ...
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Why is enthalpy and not heat released by system used while calculating entropy of surroundings?

While finding the sum of change in entropy of the universe and thus defining Gibbs free energy, why is the change in entropy of surrounding the negative of enthalpy of the system divided by the ...
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146 views

Relation between enthalpy and internal energy for chemical reaction at constant volume

Question The combustion of benzene(l) gives $\ce{CO2(g)}$ and $\ce{H2O(l)}.$ Given that the heat of combustion of benzene at constant volume is $\pu{-3263.9 kJ mol-1}$ at $\pu{25 ^\circ C}$; heat of ...
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Does all fire only emit light on its outermost shell?

This question is about light emission, which may overlap with physics, but I am most interested in combustion and types of flame (incandescence, petrochemical fuel flames, nuclear ractions). Consider ...
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Cooling down from −78 °C to −88 °C without cryogenics

Say I have a gas cylinder with nitrous oxide and cool it down to −78 °C with dry ice. Is there an endothermic process/reaction that would extract the remaining heat from $\ce{N2O}$ and bring it down ...
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67 views

What did I do wrong in my temperature change calculations?

I am doing an online assignment where I am being asked to find temperature change but there is something wrong in my calculations as I am getting the answer wrong. Can someone help me figure out where ...
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Cinnabar decomposition by heating optional method?

Is it possible to decompose cinnabar into $\ce{Hg}$ and $\ce{S}$ instead of $\ce{Hg + SO2}$ with roasting and heating. What conditions need to be satisfied in the new method?
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In a heating curve, when it is plateau, where does all the energy go since the temperature does not get higher? [closed]

So between the change of phases within the matter(solid liquid gas), the temperature reaches a plateau, no matter how much heat you add to it, it just stays the same. Where did all those energy go?
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168 views

Why does higher temperature affect the rate of electrolysis?

I understand that more heat energy= higher rate of electrolysis, but can someone explain using higher-level terms why this occurs and if there are any theories or rules that explain this?
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What is non toxic to fish, has a low freezing point, and floats on water?

I am looking for a liquid that floats on water that will prevent the water from freezing (or at least slow it down). The application would be a small area (less than a square foot). It has to be non-...
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Why is the sum of two inexact differentials exact?

From the first law of thermodynamics, $\mathrm{d}U = đQ + đW$, where $\mathrm{d}$ represents an exact differential and $đ$ an inexact differential. Exact differentials correspond to state functions ...
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Any examples of reactions where simpler molecules are combined into more complex ones and are endothermic at the same time? [closed]

Can you name examples of reactions that are endothermic and simple molecules are combined into more complex ones at the same time? Like what plants do they take heat and sunlight and they synthetize ...
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Is incineration of a solid fuel complete or incomplete?

If I have some solid material like biomass and incinerate it at 1000 Celsius degrees for 15 minutes in an oxidized atmosphere within an incineration oven. As an output it gives me ash. Is the ...
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70 views

Why does water splash if you put it into a hot pan? [closed]

I had kept my tea pan on the stove (At high)for about 30seconds . I was making tea and getting the water to put in the tea pan. There was nothing in it before that .After that , I quickly poured some ...
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Verify heat produced by flame using enthalpy of fomation

I'm simulating using a CFD solver a pure oxygen/methane flame. However, I doubt that the combustion model does not produce enough heat. The heat from reaction is defined by $S_h=-\sum_{j} \frac{h_j^0}{...
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464 views

What factors promote honey's crystallisation?

Honey is a complex mixture containing, probably, more than hundred compounds. I understand that the % of those components will affect the crystallisation. However, I am wondering what factors may ...
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105 views

What causes little spikes in a flame? [closed]

I have a lighter at home which everytime I use it, generates little spikes (see picture below) which eventually disappear. The Spikes are not an effect generated by the camera. I can confirm that ...
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1answer
56 views

A lot of confusion in 1st law of thermodynamics [closed]

My sir told me that Total energy of system = K.E + P.E in starting. Then Change in energy = F(External force on body ) * displacement of walls. Then from here , change in energy = W+q. (Don’t ...
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Help in understanding first way of changing the state of system

There is a statement in my book: THERMODYNAMICS One way: We do some mechanical work, say $\pu{1 kJ},$ by rotating a set of small paddles and thereby churning water. Let the new state be called $\...
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1answer
124 views

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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2answers
70 views

Oxygen generator, heat driven, from air

What chemical can be used to absorb $\ce{O2}$ from the air at normal temperature and pressure, then release the $\ce{O2}$ at normal pressure and elevated temperature, below $\pu{900 ^\circ C}$ ($\pu{...
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Searching for a fireproof sponge?

(I know this is a bit off topic, but I don't know where else to ask. If you know a better StackExchange site, please tell me) I'm working on a project, and I want to basically create a "flaming ...
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1answer
61 views

How to break bonds of tea on a curtain? [closed]

If I throw tea on my curtain , it looks as if the curtain has absorbed tea molecules but is it true to say that since matter has spaces between them.So these tea molecules go into that space and stick ...
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35 views

Energy loss in the process for exothermic reactions

Some chemical reactions while producing the product molecules releases heat to the surroundings and such reactions are called “exothermic reactions”. Is it true that such systems must be showing ...
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Question to find increment in total energy of a sample of He gas? [closed]

If a closed rigid wall container filled with 20 gram of Helium gas moving at a constant speed of 10 m/sec is stopped abruptly to stand still, find the increment in temperature of this He sample. Way I ...
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How does heat transfer between molecules happen in deep?

Inside the container is cold water and outside the container is hot water. B is the microscopic view of container walls .W is water And A is hot water. What I have shown is the microscopic view of ...
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237 views

Which has more internal energy, a bucket of hot water or a bucket of cold water

Online answer I found : The bucket of hot water has more internal energy. Internal energy depends on the amount (mass) of substance and the kinetic energy of the molecules of the substance. My ...
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3answers
84 views

What is the difference between fire and warm body? [closed]

A burning body has flames (Candle flame)whereas a hot or warm body (warm utensil or body being hot but doesn’t burn )is just very hot. Keeping hand near a burning body makes you feel hot but not ...
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Does hot water dissolve Copper more than cold water?

I read from WA state dept health https://www.doh.wa.gov/portals/1/Documents/pubs/331-178.pdf that hot water disolves copper more copper than cold water. Use cold water for drinking and cooking. ...
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75 views

Thermodynamics heat, enthalpy, Gibbs

We know the basic Thermodynamic equations are: $$ dU=-PdV+ TdS + \mu dN$$ $$ dH=dU+d(PV)= TdS+ \mu dN + VdP$$ we typically assume constant Pressure for a reaction carried out in air and neglect the dP ...
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Good Hess's Law experiment [closed]

I am doing an Internal Assessment for my IB chemistry class, and I want to do something on Hess's Law, and I'll be doing it simulation based, using this website. With the solutions and equipment on ...
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152 views

Specific Heat Derivation

The specific heat capacity at constant volume and the specific heat capacity at constant pressure are intensive properties defined for pure, simple compressible substances as partial derivatives of ...

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