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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making tire material [closed]

I was thinking about how to make tire material from home. I know that the materials are rubber, steel, nylon and a few other things. Does anyone know if it would be possible to heat press these ...
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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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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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Is heat a form of energy or is it just a transport of energy, not energy itself?

In every textbook I read, it says that heat is a form/type of energy... but in lecture, my professor said, that there is no such energy as heat and that heat is just a method by which we can transport ...
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How is pumping “Air” into a bicycle make dW (delta work )negative , when in fact there is a increase in pressure and a slight increase in volume? [closed]

Considering that it's an adiabatic process hence $\mathrm dQ=0$, and $\mathrm dU=\mathrm dW$. And since the work is done on the system then $\mathrm dW$ must be positive. (The answer which is in the ...
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Does heating potato starch destroy its resistant starch?

Resistant starch, as found in potato starch, is supposed to have health benefits. There are differing opinions on whether or not heating potato starch destroys the resistant starch in it and thereby ...
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Strange Distillation Behavior

I was attempting a fractional distillation with 1mL water and 1mL propylene glycol, and I’ve been encountering strange behavior with the heating of the mixture. The heating curve shows strange “spikes”...
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Can single molecules of C and O2 react in isolation, and if so how will momentum be conserved?

I am trying to figure out how is it possible to reconcile the reality of exothermic reactions, which means that kinetic energy is transferred to (heats) the surrounding matter, with the principle of ...
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2answers
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How does the calorimeter affect heat released by the system (q)? [closed]

Here are the 2 questions I am pondering about How would the calculated quantity of heat (q) released by a system differ if the calorimeter's heat capacity was taken into account? My thought process ...
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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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Can carbon dioxide be reduced to carbon monoxide and oxygen to produce energy?

There are lots of questions about reducing or burning CO2 to carbon and oxygen to solve climate change, but of course that wouldn't work because it takes a lot of energy. But carbon monoxide is more ...
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How does a change in pH affect the colour of a leuco dye in a thermal paper?

I am investigating the way that a leuco dye is released in thermal paper once heated. I have understood that leuco dyes, when in their colourless state are encapsulated in an acid developer in the ...
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Why does branching increase stability? [duplicate]

The heat of combustion of neo- pentane is lower than n-pentane.This clearly means that neo-pentane is more stable than n-pentane.What is the reason for this?
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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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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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Thermochemistry questions regarding enthalpy [closed]

I have a few questions about heat of combustion. I have two different scenarios that I was to present: Scenario 1: Given heat of combustion in the equation $\ce{CH4 + 2O2 -> CO2 + H2O}$ and $\Delta ...
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Boilling colloidal silver?

I have some colloidal silver that i bought from a shop. It is 18ppm, however, I need a higher PPM and I can't seem to buy it anywhere where I live. If I boil this colloidal silver, would it make the ...
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Re-Fusing (Unsplit) Cracked Glassware

If I heat up cracked glassware (wherein a crack has gone through part of the glass without any glass splitting away) will it cleanly refuse together before the whole piece loses its shape? If so, ...
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67 views

When can you use the direct flame of a Bunsen burner, and when must you boil a beaker of water first?

I'd like to ask when you would do the following: use the direct Bunsen flame to heat a substance; place the substance in a test tube, which is placed in a beaker of water, then boil the water with the ...
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Heat Transfer Coefficient Problem

The Problem An unusual reference gives the formula below for the heat transfer coefficient of an emulsion. $$H = 0.0061\left(X^{0.6} + 0.038T\right)\cdot V^{0.35}$$ In the formula $T$ is the ...
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How can a thermometer ever show the actual temperature of an object if the object loses heat to the thermometer?

We know that when two objects are placed in contact with each other, after a period of time, the two objects will have the same temperature. Thus, if a hot body comes into contact with a relatively ...
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Latent Heat, Vapor pressure and Equilibrium [duplicate]

So after reading about this topic i wanted to share what i learned and i wanted you guys to tell me if what i am writting is correct: A pressure vessel has propane inside and it is pressurized. The ...
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Cis-Trans Isomers Heat of Combustion

Consider the 4 cis-trans isomers for the above compound. In what way would the cis-trans isomers affect their heat of combustion. I think that if the substituents are on alternating sides of the ...
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Gibbs–Helmholtz equation

The Gibbs–Helmholtz equation was developed in the 1870's, while Nernst's heat theorem was developed in the early $20^{th}$ century (according to google/wikipedia). Nernst's heat theorem tells us that ...
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Confusion on when to use mass of entire solution when performing q=mc∆T

I hope you are having a good day. I am studying for the AP Chemistry exam in May 2020. While studying, I encountered a doubt. In Problem 1 (the question on the top), the educator saw that the ...
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Change in temperature if salt is dissolved in water with different initial temperatures

I will mix a salt with room-temperature water and 8 degree Celsius water. Then I will compare the heat of solution with each other. Does the initial temperature of the water affect how much the heat ...
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What exactly is temperature?

I've read at many places that temperature is the average kinetic energy of particles present in an object. I just don't intuitively get how kinetic energy is connected with temperature. And how is ...
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Heat transfer to an ideal gas [closed]

In thermodynamics, why is the heat that is transferred to an ideal gas considered as work that was done on the system for an isothermal process?
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Understanding the term 'heat of hydrogenation'

From Chemistry Libretexts: Heat of hydrogenation (symbol: $ΔH_\mathrm{hydro}$) of an alkene is the standard enthalpy of catalytic hydrogenation of an alkene. Does the heat of hydrogenation include ...
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At what temperature does a polyester release toxic gases?

I've bought a "Shrinky Dinks" printable sheets and now I'm feeling unsure about using it since I've read that heating polyester materials may be very harmful for health, and the final purpose of this ...
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Strong exothermic mixing of two 'safe' liquids

I have read (thanks to Stack Exchange) that mixing water and sulfuric acid is exothermic, as is NaOH and HCl. Are there two 'safe' liquids that can be mixed and produce anywhere near the same amount ...
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Determining the Heat Capacity during a combustion in a bomb calorimeter

The combustion of $\pu{2.350 mmol}$ of $\ce{X}$ caused the temperature of a bomb calorimter to rise from $23.700 °C$ to $26.300 °C$. Assume $T = 25.000 °C$, $H_\text{comb} = -3310 \frac{kJ}{mol}$, and ...
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Regarding the infinitesimal form of the First Law of Thermodynamics

First Law of Thermodynamics is expressed as[1] The internal energy of an isolated system is constant. If $w$ denotes the work done on a system, $q$ for the energy transferred as heat to the system,...
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How to determine the expression of polytropic specific heat and the rule of polytropic transformation? (Thermodynamics)

This is how i manage to solve this question, any feedback is welcome. Also, if you feel that this is not easy understandable, feel free to add comments. I will drop a link to this file in my drive. ...
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Can dissipative work be circumscribed as irreversible heat transfer

My question refers to an article I read yesterday in which the author states that for the calculation of the entropy change for a process (in that case friction, during an irreversible adiabatic gas ...
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Acid-Temperature coagulation of milk

I was making coffee with a cup of boiling milk which was 2 days old. I used instant coffee powder and some sugar for the making of it. Tried to make a very hot coffee but usually prefer medium hotness....
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Enthalpy of formation for Lithium ion in ethylene carbonate

The following link has the enthalpy of formation for aqueous lithium http://nshs-science.net/chemistry/common/pdf/R-standard_enthalpy_of_formation.pdf I am wondering how to get the enthalpy of ...
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Does calcium nitrate decahydrate dehydrate or decompose upon heating to 100 degrees Celsius? [closed]

Consider a sample of $\ce{Ca(NO3)2.10H2O}$. To remove water, I need to heat it to $\pu{100 ^\circ C},$ but will this high temperature decompose it or will I get the anhydrous salt?
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Irreversible isothermal expanison when given final and initial pressure but not external pressure

I'm asking about the second part of the question. So for isothermal, irreversible expansion, w = -Pext *change in volume. I calculated V2 through the fact that p1v1=p2v2 since isothermal. For V2, I ...
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When Cp = Cv + R

So in a physics test question, there was this question when is $C_p$ not $C_V + R$? And I wrote: when number of molecules change. Because the derivation of above formula comes from $nC_p\,\mathrm dT -...
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Will the temperature of a faucet actually be lower than the countertop or will it only feel cooler due to specific heat?

Due to specific heat capacity of metals, they feel cooler because they don't retain as well as other materials. But is their temperature actually lower if it could be measured?
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Clarification required on whether to use $C_v$ or $C_p$ in this question on finding entropy change

$1 \text{ mol}$ of an ideal monoatomic gas at $300 \text{ K}$ is subjected to a reversible isentropic compression process until final temperature reaches $600 \text{ K}$. If initial pressure is $1 \...
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How to calculate the temperature change when CaCl2, NaCl, and water added together at an initial temperature of 298 K?

My question: How to calculate the temperature change when adding $\pu{0.1 kg}$ of $\ce{CaCl2}$ and $\pu{0.1 kg}$ of $\ce{NaCl}$ to $\pu{1 kg}$ water with an initial temperature of $\pu{298 K}$? I ...
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Steam rises when the heat supply stops

When water boils and you suddenly shut the heat off, a lot of steam arises from it just after you shut the heat off. Why this happens, I thought that maybe water condenzes very fast in small droplets ...
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Determining heat capacity of gasses

I need a little help on answering a question which popped into my head while I was reading about gas laws: Suppose that I have three canisters, each holding a different gas of unknown identity [...
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Hess's Law and ΔH

Target equation: $\ce{Mg(s) + 1/2 O2 -> MgO(s)}$ $$ \begin{align} \ce{MgO(s) + 2 HCl(aq) &-> MgCl2(aq) + H2O(l)} &\quad ΔH &= \pu{-1300 kJ} \tag{1}\\ \ce{Mg(s) + 2 HCl(aq) &-&...
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Why could it be assumed that the standard enthalpy change is independent of temperature down to 25 °C?

For the reversible reaction of pyruvic acid to 2,2-dihydroxypropanoic acid, we calculated enthalpy using NMR and extrapolated from area (integration) and peaks etc. We then plotted $\ln K$ vs $1/T.$ ...
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249 views

Why does ice get colder when you add salt? [duplicate]

I know that when you put salt on ice it may turn to a slush and it does feel cold. What is the reason for this?
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Deciding the order of heat of combustion of isomeric alkanes

I'm asked which one of the alkane has the lowest heat of combustion (note: the question says heat, not enthalpy) and according to the answers, the right one is d. I'm trying to understand why d ...

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