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].
516 questions
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Is entropy constant when no heat is transferred?
Does entropy remain constant in when no heat is transferred between the system and surroundings?
If I do only mechanical or electrical work to change the properties like the volume of the system, ...
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how is energy conserved during this phase change?
learning about an HVAC system has confused me regarding some basic science principles. if I have a closed container of a fluid in vapor state and this container is at a lower temp than the ...
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Deriving the relationship of Cp - Cv in terms of P, T, V, and H
We're learning the relationship between Cp and Cv. We seem to be doing it a little uniquely because we're looking for equations of Cp - Cv in terms of P, T, V, and U, and in terms of P, T, V, and H
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Entropy change in isothermal reversible expansion
So, this question is of JEE Mains 2023 exams.
One mole of an ideal gas at $350K$ is in a $2.0L$ vessel of thermally conducting walls, which are in contact with the surroundings. It undergoes ...
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How to calculate the specific heat capacity of a non-ideal heterogenous mixture/suspension with four components?
I need to calculate the specific heat capacity of a non-ideal mixture of glycerol (liquid), ammonia (liquid), water (liquid) and biomass (solid). What would be the best way to approximate the specific ...
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Can liquid hydrogen be oriented along a single axis?
I ran into a fascinating little fact I didn't remember hearing before: if H2 is cooled below 60 K, its heat capacity looks like that of a monoatomic gas. It simply doesn't have enough thermal energy ...
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Is there water coloring that will maintain color at 80°C?
I'm building a keg cleaner for my employer. The cleaner has a caustic tank that uses PBW, and a sanitizer tank. The current build is plagued with caustic contamination, so I would like to see ...
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Theoretical justification for the definition of standard enthalpy of reaction
I've been reading the book Chemistry: Core Concepts by Allan Blackman, Daniel Southam, Gwendolyn Lawrie, Natalie Williamson, Christopher Thompson and Adam Bridgeman. They give the following definition ...
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Calculating the heat of reaction between sulfuric acid and sodium hydroxide
For my lab report I have to calculate the theoretical heat of reaction $\Delta H_{\text{rxn}}$ between sulfuric acid $\ce{H2SO4}$ and sodium hydroxide $\ce{NaOH}$ using their heat of formations. The ...
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Two different approaches for calculating enthalpy change for methane + HCl
I know that $\Delta{H}=H_{products}-H_{reactants}$ and also we can use $\Delta{H}=\Sigma{H}_{bonds broken}-\Sigma{H}_{bonds formed}$.
Take the example of methane + HCl. If you calculate the total ...
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Why are internal energy and work mentioned in a question about exothermic or endothermic systems? [closed]
This is a question from my chemistry homework. Note the explanation below.
A 100.0-g bar of gold is heated from 25°C to 50°C during which it absorbs 322 J of heat. The volume of the gold bar remains ...
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Weird jumps in DSC measurements between scans
I have multiple DSC measurements with multiple up- and down-scans and some of the time, seemingly at random, the inflection points will show massive jumps in the heat flow. I have no idea where they ...
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Heating a Single Water Molecule [closed]
From my understanding, phase changes break/form bonds between molecules of the same substance. Assuming this is in a vessel at 1atm of inert gas, if I have one molecule of water with no bonds to other ...
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Definition of Gibbs Free Energy and its interpretation [closed]
RELATIONSHIP BETWEEN $\Delta G$ & $W_\mathrm{non-PV}$
$dU = dq + dw_\mathrm{py} + dw_\mathrm{non-PV}$
for reversible process at constant T & P
$dU+pdV-TdS = dw_\mathrm{non-PV}$
$dH-TdS = dw_\...
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How to measure heat transfer and heat dissipation in a kitchen? [closed]
I am a chemistry beginner just starting to coming to grips with stoves and Bunsen burners.
I would like to know, what kind of instrument can I use to measure the amount of heat transferred from a ...
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Heat capacity of calorimeter
The problem is:
$\pu{30 mL}$ of water at $\pu{24.00 °C}$ were stored in a calorimeter in a laboratory experiment. Then, $\pu{40 mL}$ of water at $\pu{55.00 °C}$ were added to the calorimeter ...
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Spontaneity of endothermic reactions [closed]
I see the Gibbs Free Energy explanation everywhere, but is there an intuitive explanation of how endothermic reactions can happen spontaneously? It seems intuitively reasonable that heat flows from ...
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Why potassium carbonate breaks glass when heated? [closed]
I have been studying about desiccants for a while and testing some inorganic salts, including calcium chloride, sodium sulfate and potassium carbonate. When they get enough moisture from air, I ...
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Possible error in textbook question? (Heat transfer)
I am dealing with either (a) a severe misunderstanding of the question, or (b) a wrong textbook answer.
Here is question verbatim:
A jacketed vessel is used to heat a water stream using steam
...
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How can I model the melting of ice as a function of time?
How much time it will take for a ball of ice at 0 °C and radius 3 cm submerged in 1 l of water at 100 °C to completely melt? (Assume the ice melts completely uniformly and treat it as a shrinking ...
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Calcium oxide in self-heating packs [closed]
I've read some articles on the internet about self-heating meals. Heat released from an exothermic reaction is used to heat up the food. In fact, several reactions are recommended for this purpose ...
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Can heat cause the excitation of argon
Can argon be excited by heating? I work with a process that involves heating titanium to 500c-1000c in an argon environment. On our camera, the material looks purple when heated, the same shade as ...
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Can a colorant be mixed into zirconia powder?
I’m wanting to color zirconium dioxide into beads after it is fired but I would like to get more colors than just white and the high temperature black oxide. Can I mix other metal oxides to zirconium ...
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Understanding the Role of Gibbs Free energy and Enthalpy as the energy required to drive a reaction
I was looking at the enthalpy change for water-splitting reaction:
$$ \Delta H^o_R = [\Delta H^0_{H_2(g)} +\frac{1}{2}\Delta H^0_{O_2(g)}]-\Delta H^0_{H_2O(l)} = \pu{285.83 kJ/mol}$$
According to ...
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Is the "heat or UV" necessary for PVC10 + Cl => CPVC10 catalytic or endothermic and if endothermic how much energy?
Production of Chlorinated PolyVinyl Chloride (CPVC) from PVC and chlorine requires incorporating about one part chlorine in 10 PCV to achieve around 63% chlorine mass CPVC. This reaction is "...
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Why is there internal energy change in a bomb calorimeter?
In a bomb calorimeter, the reaction occurs at a constant volume, hence we say that the heat absorbed by the water in the surroundings is equal to the change in internal energy for the reaction. But, ...
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Is the liquid in this question water? How can one know for sure? [closed]
I have been studying and there is a question in my book asking:
A faulty thermometer reads freezing and boiling point of a liquid as -5°C and 95°C respectively on the Celsius scale. What is the ...
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calculation of enthalpy change
So for for the calculation of $\Delta{H}$,we have two formulaes in our book:
$\Delta{H}=E_{2}-E_{1}$
where $E_{2},E_{1}$ are the internal energies of the product and reactants respectively.
Now this ...
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Does seawater foam more when its warm? And if so, why
I work at an oil rig out in the sea.
We are pumping seawater into the rig, and back out again after it has gone through the system.
Its really warm outside now, and when we are pumping seawater into ...
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Is heat treatment the only way to increase grain size in steel?
Heat treatment is a well-established method for increasing grain size in steel. Is there any other approach known to man? I cannot seem to find anything via web search.
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Can we mix non polar and polar molecules by providing heat? [closed]
Polar molecules don't dissolve with non polar molecules because of difference in forces of attraction between them. But if we provide enough heat will they mix?
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Why do lipids decrease in viscosity with increasing temperature? [closed]
Is the answer simply that the carbon bonds break up and that the molecules get smaller?
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What factors determine the distribution of chemical energy between work and heat in a chemical reaction? [closed]
In the context of a chemical reaction, what factors determine the allocation of chemical energy between performing pressure–volume work and generating heat? Are there any key parameters or variables ...
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Chemical equation of wood to charcoal pyrolysis
The equation for the perfect burning of wood is approximately:
$$\ce{C_xH_yO_z + VOCs + O2 -> CO2 + H2O + volatiles + heat}$$
Where $\ce{C_xH_yO_z}$ represents the cellulose and lignin and VOCs are ...
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Is q=0 for irreversible adiabatic process?
Well, I am a little bit confused about this question. I learn that reversible adiabatic processes are isentropic. So $\Delta S=0$. Through $\Delta S=\frac{ q}T$, we can say that $q=0$. But if you take ...
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How is the reason for “why neutralizing weack acids with strong bases gives less heat” that the heat is used in ionizing the acid?
In my lab manual this is written but I can’t see how this is true
The heat of neutralization of weak acids by strong bases is less than 13.7 Cal/mole because the weak acid becomes completely ionized ...
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Heat transfer calculation in open tank equalization
Thanks for your replies guys, sorry for unclear and undefined question. Let me try to reparaphrase my question.
Updated info:
This is the way i try to solve this problem.
I calculate the pipe length ...
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Is there any chemical that can react with two different chemicals to generate heat or cold? [closed]
For example. There are three chemicals. Chemical A,B,C
Chemical B react with Chemical A = heat
Chemical B react with Chemical C = cold
Is there any chemical available like this? And is it safe to ...
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Do whey proteins precipitate with heat?
I am currently studying about the biochemistry of yoghurt and when reading about the effect of heat in milk proteins specifically whey, my book says that heat can denature whey proteins.
So after the ...
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Does a higher concentration of Methanol to Water increase or decrease heat absorption?
I have a ground source heat pump with a relatively high concentration of methanol in the ground loop. See this post.
When the system is running, the fluid in the ground loop comes in at about -3.3°C ...
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What is the entropy change in isochoric process
I have studied that entropy increases with increase in temperature and it decreases with increase in pressure but in case of isochoric process both are happening at the same time but still the overall ...
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How exactly is heat supplied in an isothermal process
How exactly is heat supplied in an reversible isothermal process. If the temperature of system and surroundings always remains the same, then how come surrounding is supplying heat?
I studied that T ...
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Is delta S of universe always 0 when an ideal gas undergoes an isothermal irreversible process?
Since for an irreversible process,
$$dS_\mathrm{Surrounding} =-\frac{\text{dq}_\mathrm{irr,sys} }{T_{\text {surr }}}\tag{1}$$
where $\text{dq}_\mathrm{irr,sys}$ is heat exchange of system
and $-dq_\...
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Chemistry Thermodynamics and Sign Convention [closed]
Can anyone pls explain me the sign conventions that we use in chemistry thermodynamics for heat and work...also kindly explain how to identify what will happen to heat in positive or negative work and ...
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How can the heat equation be used to model temperature vs time in a solubility experiment?
Background:
I am doing experiments trying to map the practical solubility of a certain chemical species called an "activator" solution. This solution is essentially a sequential mixture of ...
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Enthalpy and Bond Energy Sign Convention
I read that a negative enthalpy of formation means an exothermic reaction. Does that mean this reaction is true? The enthalpy of formation for $\ce{H_2O}$ is -285.8 kJ/mol.
$$\ce{2H2(g) + O2(g) -> ...
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Which heat pad content materials will keep me warm the longest?
I am trying to find a good heating pad/bag for myself that keeps me warm for as long as possible (nonelectrical, heated once, then used until it gets cold). The classic is a hot water bottle, and ...
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Confused why delta ∆Q and dQ don't make sense for heat Q
In my chemistry teacher's notes, some notations concerning the heat $Q$ are marked as inappropriate.
$Q$: yes
d$Q$: no
$\delta Q$: yes
$\Delta Q$: no
In the second bullet in the screenshot below, ...
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Is mass of solute included in calculation of enthalpy of solution? [duplicate]
$$
\begin{array}{lrrrr}
\hline
& \ce{MgSO4} & \ce{K2SO4} & \ce{KNO3} & \ce{NH4NO3} \\
\hline
m/\pu{g} & 15 & 15 & 15 & 15 \\
M/\pu{g mol^-1} & 120.37 & 174.26 ...
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Intuitive explanation for enthalpy of hydration
In my chemistry course, we were discussing types of enthalpy and the enthalpy of hydration came up. My instructor defined this as
heat associated with adding water to an anhydrous salt.
However, I ...
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