Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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].

-1
votes
0answers
22 views

If water vapour is assumed to be a perfect gas… Calculate the internal energy change when 1 mole of water is converted to ice

If water vapour is assumed to be a perfect gas, molar enthalpy change for vapourisation of 1 mole of water at 1 bar and 100 C is 41 KJ/mole. Calculate the internal energy change when 1 mole of water ...
0
votes
2answers
27 views

Is paper aging(oxidation) and paper burning(rapid oxidation) the same thing?

I woke up today with a question of what is fire; looked up the definition and the first response was that fire was rapid oxidation. I was curious what the difference was between rapid oxidation and ...
-3
votes
0answers
33 views

AP Chem Question [on hold]

How many kilojoules of heat are absorbed when 1.25 mol $\ce{H2O}$ is converted from liquid at 15.0℃ at vapor at 25.0℃? The specific heat of $\ce{H2O}$ (l) is 4.18 $\pu{J//g*℃}$. The heat of ...
0
votes
1answer
52 views

Is it safe to heat fluorite (CaF2) to 140 °C?

For the manufacture of the optical system, we need to heat the fluorite ($\ce{CaF2}$) lenses to $\pu{140 °C}$. Is it possible: for some poisonous gas to be emitted? ($\ce{F2, HF}$ or other) for ...
0
votes
0answers
18 views

Specific Heat of Metals

Two solid metal objects are placed into boiling water and allowed to reach equilibrium. Each is then lifted out and immediately placed into separate beakers each containing 1 liter of 10.0°C water. ...
3
votes
1answer
62 views

Why do we use Δ to mean heating?

To express heating, we usually use $\Delta$ over reaction arrows like \begin{align} \ce{CaCO3 ->[\Delta] CaO +O2}. \end{align} Why do we use $\Delta$ to mean heating during chemical reactions? I ...
0
votes
1answer
58 views

Why does the temperature remain constant during freezing?

I know it's the most silly question one could ever ask but why is that so? I am aware of what latent heat means and I also know it has something to do with freezing too. Say I have with me, a mug of ...
0
votes
1answer
53 views

What is the substance with the highest specific heat?

I always learned that water has the highest specific heat, but I recently saw that Hydrogen has a specific heat as high as 14 cal/gC and helium has a specific heat of 5 cal/gC, which would be much ...
3
votes
2answers
52 views

Intuituve reason for the constant of proportionality 2/3 in pv=nRT=(2/3)U

Why is there a $\frac23$ term? I fully understand that it makes sense for pressure to be the volume weighted average kinetic energy. And the equation above shows that this is so (for an ideal gas). I ...
-1
votes
1answer
55 views

Calorific value of a gas in combustion

The Wikipedia article on heat of combustion says: The calorific value [...] may be expressed with the quantities: energy/mole of fuel energy/mass of fuel energy/volume of the fuel ...
2
votes
1answer
57 views

Diluting methanol in water: is it exothermic?

Can someone explain in simple terms why does temperature increase when mixing water with methanol? I do not have a strong background in chemistry, but I usually have to mix both liquids (sometimes ...
1
vote
1answer
36 views

Heat generation in exothermic reactions [duplicate]

Im thinking specifically of N2 + 3 H2 ⇌ 2 NH3. Its an exothermic reaction, therefore heat is generated. Im trying to understand how Chateliers principle interacts with this reaction. I understand that ...
-1
votes
1answer
61 views

Heat transfer problem

For this problem, I'm wondering if the thermos should be involved in the heat transfer because right we have an equation in calorimetry: $q_\text{warm} =-(q_\text{cold} + q_\text{cal})$ A 125 g ...
1
vote
1answer
26 views

Specific heat problems [closed]

I am in need of help for my understanding in specific heat capacity. To be honest, I understand the lesson effectively, However, just a few days ago, I've encountered two similar yet different-in-...
0
votes
0answers
65 views

distillation of aqueous CAN solution for the purpose of a reversible and strong endothermic reaction in cool packs

I know calcium ammonium nitrate (CAN) is used for cold packs. By bending a small metal plate the salt gets dissolved in water (separated pack) and this process is endothermic. I would like to heat ...
11
votes
1answer
1k views

Why would a ~1 cm thick layer of argon be a significantly poorer conductor of heat than air?

In yesterday's new Periodic Video, Argon (new) - Periodic Table of Videos, after about 07 min 00 sec, Sir Martyn Poliakoff says: The final, and I have to admit perhaps slightly boring application ...
0
votes
1answer
39 views

Flexible & thermally conductive materials? [closed]

Quick question: Are there any common or easily obtainable materials that are thermal conductors, but also flexible? By flexible, I mean along the lines of a plastic bag, with similar or greater ...
1
vote
0answers
126 views

What is the specific heat and latent heat of an ethanol-water mixture?

How do I find the specific heat and latent heat of ethanol-water mixture? Let’s say the mole fraction of water is 0.3 and ethanol is 0.7. I am working on a project and needed values for these and ...
0
votes
0answers
35 views

Extraparticle transport limitations in het. catalysis: Varying Damköhler without affecting the external prater number (and vice versa)

Solving a question for exam preparation; In the lecture script it is asked: 1. When both external MT and HT limitations exist, derive a solution from the general mass and energy balances in terms ...
1
vote
1answer
61 views

Heat of Combustion

Methanol ($\ce{CH3OH}$) is regarded by many chemists as a possible liquid fuel for the future. The combustion of methanol occurs according to the equation: $$\ce{2CH3OH(g) + 3O2(g) -> 2CO2(g) +...
0
votes
0answers
61 views

Are there alternatives to sodium acetate?

I am wondering if there are any non poisoning alternatives to sodium acetate, which is used in those self-heating pads, that reaction can be kicked off by clicking a small metal plate? Specifically ...
-1
votes
2answers
194 views

Why do aluminum and air have low specific heats?

According to Wikipedia, ...specific heat capacity is a function of the structure of the substance itself. In particular, it depends on the number of degrees of freedom that are available to the ...
1
vote
3answers
565 views

Why are calorimeters often made of materials with low specific heats?

When building calorimeters, a material with a low specific heat is often used (such as Styrofoam, aluminum, etc.). However, why would a material with a low specific heat be preferred? My thought ...
0
votes
1answer
41 views

Where can I find the total enthalpy and heat of dissolution in water of a given components?

I don't really have a background in chemistry but I'm actually studying in aerospace engineering, sorry if this question may seem trivial. I am interested in the decomposition process of the hydrogen ...
1
vote
1answer
37 views

Predicting the temperature of an object using the heat of its surroundings after a certain amount of time?

how would you predict what the temperature of something would be if it spends a certain amount of time exposed to heat from its surroundings? is this possible? ex. what temperature would a hot ...
4
votes
1answer
78 views

How do you stop a Pharoah's Serpent reaction?

I am a novelist and working on a book. I have been searching google for an answer to the above question. How does one stop a Pharoah's Serpent reaction? Thanks!
-1
votes
1answer
250 views

Calculate Heat of Atomisation [closed]

What is heat of atomisation of P4O6(s) Given heat of sublimation of P4O6 is x kJ/mol & P–O bond energy is y kJ/mol. What is heat of atomisation of P4O6(s) Given heat of sublimation of P4O6 is x ...
0
votes
1answer
35 views

Can air inside a high temperature (1300C) Kiln cause an explosion?

I saw many kiln designs that lack an opening for hot\pressurized air to come out , or any pressure valve. But when air is heated to such a high temperature (1300C) inside a closed chamber (the kiln), ...
1
vote
2answers
54 views

Sign of work done by the system in first law of thermodynamics equation

In the equation, $\Delta E = q - W$, according to my book, $W$ is positive when it is done by the system and negative when it is done on the system. But in this problem: $\pu{3600 kJ}$ heat is ...
3
votes
0answers
137 views

The sign of enthalpy of formation of magnesium oxide

I'm currently doing a lab to calculate the enthalpy of formation for $\ce{MgO}$. However at the moment me and my lab partner are having a disagreement. We've both calculated and agreed upon the same ...
2
votes
1answer
56 views

Is there any difference between “autoignition temperature” and “ignition temperature”? [closed]

Is there any difference between the "autoignition temperature" and the "ignition temperature" of a substance?
0
votes
0answers
44 views

Is there a direct relationship between specific heat and either thermal conductivity or heat transfer?

I am currently teaching high school chemistry, but my background is in physics. Our curriculum states that specific heat capacity is the amount of thermal energy required (or released) per 1 gram of a ...
0
votes
2answers
53 views

Fried potatoes absorbing oil [closed]

Suppose we bring a pan and put in it some oil and turn on the heat, before the oil could get very hot and nearly boiling, we put on the potatoes that start frying. Someone told me that if the ...
0
votes
1answer
39 views

What would happen if you heat volatile/flammable material in a vacuum? [closed]

Fire is an oxidizing chemical reaction, in the simplest sense it needs oxygen and fuel to burn in order to stay alight. But what reaction would you observe from a flammable substance like gasoline or ...
0
votes
1answer
60 views

Can heat capacity at constant volume for a gas decrease as temperature increases? [closed]

I found a function for the $C_V$ of a gas which is being heated under constant volume,but the function shows that the $C_V$ is decreasing. I was wondering if this is possible for any gas since I know ...
5
votes
1answer
63 views

slow down ice melting in water

Having to separate freshwater crabs for commercial fisherman while on the boat, we dump the crabs in ice water, as crabs aren't as aggressive and bite less when cold. There's only so much room on the ...
1
vote
2answers
85 views

Why don't we consider VΔP when we define Q?

We only define $Q = \Delta U + W_\text{exp}$ (expansion work = $-P\Delta V$). If heat can cause $\Delta U$ and work, why work is defined only as expansion work in the first place where there are other ...
-1
votes
1answer
63 views

Thermodynamics energy balance question help

I made the following attempt to solve this question.However I don't know how to find final pressure.I don't know how to find final temperature for both sides.Can you give me a hint?
-4
votes
1answer
50 views

Enthalpy of formaton [closed]

today I was doing a set of HW problems regarding enthalpy and stumble upon one problem that I found confusing.It was the standard enthalpy of formation for CaCO3 is -1207.6 kJ mol when 30.7 g of ...
2
votes
0answers
71 views

Does specific heat capacity of the container have an effect on the exactitude of a calorimetre?

I'm doing a lab on what is the best material for a calorimetre. I chose glass, aluminum, styrofoam cup, paper/cardboard cup and a plastic cup. I've found that the cardboard cup was the best followed ...
4
votes
1answer
140 views

Why might copper have a lower heat capacity than lithium according to the Shomate Equation?

I've learned that according to Condensed phase thermochemistry data, according to NIST, the functions of heat capacity, enthalpy, and entropy can be predicted by the Shomate Equation: $$\begin{align} ...
1
vote
1answer
172 views

Material that changes color when changing phase from solid to liquid [closed]

I was asked and am wondering myself, what are materials that change color when molten? I could not find any examples online, but it really interests me. I would to get some examples which have one ...
3
votes
2answers
102 views

Can the change in the entropy of the surroundings always be obtained by dividing heat transferred by the temperature at which the transfer occurs?

Consider $\pu{1 mol}$ of an ideal monoatomic gas going through reversible isochoric heating from $\pu{100 K}$ to $\pu{1000 K}$. Calculate $\Delta S_\pu{sys}, \Delta S_\pu{surr}.$ $$\Delta S_\pu{...
3
votes
2answers
4k views

Why 'Enthalpy change' (Delta H) is equal to 'Heat transfer at constant pressure' (Qp)? [closed]

Why 'Enthalpy change' (∆H) is equal to 'Heat transfer at constant pressure' (Qp)? ∆H = ∆U + ∆pV, here only expansion work done by the sustem is added. If non expansion work is done on the system then ...
0
votes
0answers
16 views

If a reactor made up of alloy has ceramic coating inside, can the temperature inside be raised to 500C?

I would like to get a reactor fabricated for plastic pyrolysis. The temperature would maintained around 520C. The material processed would be Waste Polypropylene and Polyethylene. With the ceramic ...
-1
votes
1answer
58 views

When boiling a liquid, how vapour pressure and ambient pressure get equal? [duplicate]

When boiling a liquid, how vapour pressure and ambient pressure get equal? As vapour pressure will increase, it will lead to increase in ambient pressure also. let, Initially there would be some ...
-2
votes
1answer
28 views

Heat capacity determination

Since heat capacities are determined in a calorimeter taking advantage of the known heat capacity of water, how was the heat capacity of water originally determined?
0
votes
0answers
79 views

dq/T vs. CdT/T for measuring absolute entropy

In principal one could determine absolute entropy for a substance by integrating dq/T from 0K to the temperature of interest. However, I've seen this done using heat capacities, integrating CdT/T ...
4
votes
1answer
233 views

Thermochemistry - zero heat energy

We were just wondering in our chemistry class: is there any reaction which is neither exothermic nor endothermic?
-1
votes
1answer
29 views

Won't gas thermometers break on using fixed volume of gas?

From the ideal gas equation, PV is proportional to T. Now if V is kept constant, we'll get Gay-Lussac's law. Now my question is: According to observations, we know that substances undergo a change ...