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].
501
questions
0
votes
1
answer
39
views
Why potassium carbonate breaks glass when heated?
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 ...
0
votes
3
answers
165
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
...
- 21
0
votes
1
answer
87
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 0ºC and radius 3cm submerged in 1L of water at 100ºC to completely melt? (Assume the ice melts completely uniformly and treat it as a shrinking sphere)
...
1
vote
1
answer
90
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 ...
- 57
2
votes
0
answers
59
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 ...
- 29
5
votes
1
answer
300
views
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 ...
- 53
1
vote
2
answers
69
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 ...
- 155
0
votes
0
answers
17
views
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 "...
- 211
0
votes
1
answer
157
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, ...
-4
votes
1
answer
71
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 ...
- 103
-3
votes
1
answer
54
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 ...
- 1
0
votes
0
answers
43
views
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 ...
- 19
2
votes
0
answers
29
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.
-4
votes
1
answer
98
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?
- 9
-4
votes
1
answer
53
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?
-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 ...
- 157
1
vote
0
answers
116
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 ...
- 157
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 (...
- 11
0
votes
3
answers
407
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 ...
- 13
-2
votes
1
answer
63
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 ...
- 7
0
votes
0
answers
58
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 ...
- 11
-1
votes
1
answer
71
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 ...
- 7
0
votes
0
answers
52
views
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 ...
0
votes
0
answers
55
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 ...
- 111
1
vote
2
answers
2k
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 ...
- 29
0
votes
2
answers
57
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 ...
- 29
-5
votes
1
answer
124
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_\...
- 11
-6
votes
2
answers
106
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 ...
1
vote
0
answers
65
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 ...
- 490
0
votes
0
answers
42
views
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.
$$\ce{2H2(g) + O2(g) -> ...
- 101
0
votes
0
answers
140
views
Which heat pad content materials will keep me warm the longest?
I am trying to find a good heating pad/bag for myself that keeps me warm for as long as possible (nonelectrical, heated once, then used until it gets cold). The classic is a hot water bottle, and ...
- 1
2
votes
2
answers
433
views
Confused why delta ∆Q and dQ don't make sense for heat Q
In my chemistry teacher's notes, some notations concerning the heat $Q$ are marked as inappropriate.
$Q$: yes
d$Q$: no
$\delta Q$: yes
$\Delta Q$: no
In the second bullet in the screenshot below, ...
- 37
1
vote
0
answers
78
views
Is mass of solute included in calculation of enthalpy of solution? [duplicate]
$$
\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 ...
- 11
2
votes
3
answers
107
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 ...
- 323
1
vote
2
answers
320
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 ...
- 121
5
votes
1
answer
104
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 ...
4
votes
2
answers
2k
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 ...
- 189
0
votes
1
answer
254
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 ...
- 189
3
votes
4
answers
407
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 ...
- 43
-3
votes
1
answer
331
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 ...
-1
votes
1
answer
333
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 ...
2
votes
4
answers
855
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,...
- 187
-2
votes
1
answer
181
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 ...
- 134
1
vote
1
answer
87
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 ...
-5
votes
1
answer
546
views
Can I increase the melting point of paraffin wax over 100 degrees celsius [closed]
Can I increase the melting point of paraffin wax over 100 degrees celsius at room temperature and pressure.
- 99
0
votes
0
answers
125
views
Does heat increase the hydrolysis of urea hydrochloride?
The preparation of ammonium chloride by reacting urea with HCl produce urea hydrochloride the reaction take too much time to get ammonium chloride depending on ratios.
So can heat increase the ...
user123481
3
votes
2
answers
181
views
What does the heat capacity really represent? [closed]
According to Wikipedia, heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature:$$C = \...
- 332
-3
votes
1
answer
388
views
why does sodium chloride in water dissolve/precipitate with little heat, or indeed, at all? [closed]
Sodium and chlorine presumably react together strongly, which is why the solid product is stable and takes a lot of energy to break the bonds formed, and to melt. According to the Wikipedia, melting ...
- 105
3
votes
1
answer
150
views
How can the reaction heat be ignored in an energy balance?
I have received from my professor the following (summarized) problem:
A first-order exothermic reaction $\ce{A->B}$ took place in a typical tubular plug flow reactor (PFR). The tube was cooled to a ...
- 31
2
votes
0
answers
53
views
Prigogine vs. Bronsted and the minimum entropy production principle
I apologize for the length of this question that was asked here prigogine-bronsted but got no reply; anyhow, Bronsted's name is much better known among chemists than among physicists...
Prigogine's ...
- 344