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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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 ...
J.Doe's user avatar
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-2 votes
1 answer
51 views

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 ...
Camel Camel's user avatar
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3 answers
88 views

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_\...
Sai's user avatar
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1 answer
50 views

How to measure heat transfer and heat dissipation in a kitchen?

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 ...
Joselin Jocklingson's user avatar
0 votes
0 answers
44 views

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 ...
Sherry Zakhari's user avatar
-1 votes
1 answer
70 views

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 ...
Peter's user avatar
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-2 votes
1 answer
80 views

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 ...
Clinfosfito's user avatar
0 votes
3 answers
178 views

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 ...
Lim Min Kang's user avatar
1 vote
3 answers
170 views

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 ...
DoTheMath's user avatar
1 vote
1 answer
160 views

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 ...
kamikaze's user avatar
2 votes
0 answers
67 views

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 ...
Andriy's user avatar
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5 votes
1 answer
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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 ...
Cara Loibl's user avatar
1 vote
2 answers
125 views

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 ...
RMS's user avatar
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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 "...
James Bowery's user avatar
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1 answer
329 views

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, ...
Aditya Mukherjee's user avatar
-4 votes
1 answer
76 views

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 ...
InfoDaneMent's user avatar
-3 votes
1 answer
72 views

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 ...
aiman's user avatar
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0 votes
0 answers
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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 ...
Andreas's user avatar
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2 votes
0 answers
30 views

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.
artist_and_not_EE_by_training's user avatar
-4 votes
1 answer
148 views

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?
ToLearn's user avatar
-4 votes
1 answer
58 views

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?
Emanuel Landeholm's user avatar
-4 votes
1 answer
69 views

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 ...
Authentic Melody's user avatar
1 vote
0 answers
167 views

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 ...
Adrien Hingert's user avatar
0 votes
0 answers
40 views

How is Clausius statement violated for reversible heat engines that are assumed to have different efficiencies?

I'm trying to verify that all reversible heat engines have equal efficiencies by using this diagram. Here, the second heat engine (HE2) is assumed to has higher efficiency than the first heat pump (...
asdfasdfasdf's user avatar
0 votes
3 answers
667 views

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 ...
Sanjay's user avatar
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1 answer
138 views

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 ...
Jay's user avatar
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0 votes
0 answers
65 views

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 ...
Fee's user avatar
  • 11
-1 votes
1 answer
100 views

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 ...
Weirdo's user avatar
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0 answers
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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 ...
CaptainAmerica Whyso's user avatar
0 votes
0 answers
62 views

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 ...
Gary Aitken's user avatar
1 vote
2 answers
3k views

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 ...
Shashank j's user avatar
0 votes
2 answers
65 views

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 ...
Shashank j's user avatar
-5 votes
1 answer
168 views

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_\...
Aditya's user avatar
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-6 votes
2 answers
122 views

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 ...
Atharv Zope's user avatar
1 vote
0 answers
66 views

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 ...
Hendrix13's user avatar
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0 votes
0 answers
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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) -> ...
itisyeetimetoday's user avatar
0 votes
0 answers
236 views

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 ...
Kjara's user avatar
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2 votes
2 answers
582 views

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, ...
Sid's user avatar
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1 vote
0 answers
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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 ...
Red's user avatar
  • 11
2 votes
3 answers
145 views

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 ...
Max0815's user avatar
  • 323
1 vote
2 answers
392 views

How does carbon dioxide in the atmosphere keep heat trapped?

In the classic description of how greenhouses gases are increasing the temperature of Earth's surface, shorter wavelengths of light like visible and ultraviolet (UV) penetrate the atmosphere, hit the ...
SteveRodgers43's user avatar
5 votes
1 answer
105 views

Is there any transparent see material that can endure temperatures of 2000 °C?

I was wondering if there is a transparent material that can endure temperatures up to 2000 °C without deforming or degrading. This material doesn't have to be glass, it can be plastic or a weirdly ...
Sayan Chowdhury's user avatar
4 votes
2 answers
3k views

How do you calculate the heat capacity ratio for a multi-compound gas?

Let's say I have a heat capacity ratio of 1.4 N2 and a heat capacity ratio of 1.2 for O2 (just random placeholder values no significance), and I wanted to calculate the heat capacity ratio of their ...
one two's user avatar
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0 votes
1 answer
365 views

How would one calculate the Heat Capacity Ratio for a multiple compound Gas?

So I'm attempting to calculate the heat capacity ratio (known also as adiabatic index) of a gas with several concentrations of different compounds such as N2, H2O, CO2, CH4 etc. And while I have an ...
one two's user avatar
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3 votes
4 answers
544 views

Is there a heat-based alternative to photosynthesis?

I can imagine one main disadvantage of a process using sunlight to metabolize sugars would be that wherever there is little/no sun (nighttime), plants don't grow. Heat is more abundant than sunlight ...
0x6869's user avatar
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-3 votes
1 answer
441 views

What does it mean when we say an atom has infinite energy levels/shells? [closed]

My chemistry teacher told that an atom has infinite energy shells according to Bohr model , where electron reside according to its angular momentum and energy. But in lower classes/ grades I have ...
Shinchan Nohara's user avatar
-1 votes
1 answer
447 views

Does the boiling point of ammonia hydroxide change with the ratio of water to ammonia?

My kids and I are designing a science experiment and we could use help with the ratio of water to ammonia in an ammonia hydroxide mixture. A little bit of background: Initial goal: To convert the ...
thefiddler's user avatar
2 votes
4 answers
971 views

What non-toxic non-corrosive liquids are used for heat transfer?

I have a steel vessel placed concentrically within a larger steel vessel, resulting in air-filled annulus (air gap) between the two vessel walls (figure below). Due to the existing vessel construction,...
Armadillo's user avatar
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-2 votes
1 answer
265 views

Does mayer's equation change for two mole of ideal gases or is it remains same for any number of moles [duplicate]

Mayer's Formula is given by: Cp – Cv = R But is the relation remains same for two mole of ideal gas, or is it Cp - Cv = 2R As, far as i know the number of moles are cancelled out in the derivation. ∆H ...
5 Dots's user avatar
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1 vote
1 answer
97 views

What endothermic reactions can be effectively reversed by electrolysis?

Not only newbie, but total layman here; please be patient with me. Given are either two different elements, two different molecules, or one element and one molecule (chemical A and chemical B). A and ...
Kortelly Zamatosh's user avatar

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