Heat is a form to transfer energy from one body to another or from one body to its surroundings. It is closely connected to thermodynamics, enthalpy, free energy, change in the state of matter, temperature.

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How to compare the Heat of Combustion qualitatively? [duplicate]

I have been doing practice problems in General Organic Chemistry. I got some questions that asked me to compare the Heat of Combustion of some molecules. I couldn't get any of those questions and the ...
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114 views

Does a microwave oven act on the principle of giving vibrational or rotational energy to water molecules? [closed]

Does a microwave oven act on the principle of giving vibrational energy to water molecules or by giving rotational energy to water molecules? I tried to google it but answers are not specific where as ...
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1answer
91 views

Calculating temperature after adding heat to ice

If $53.2~\mathrm{kJ}$ of heat are added to $15.5~\mathrm{g}$ of ice at $-5^\circ\mathrm{C}$, what will be the resultant state of matter in which water is present and also calculate its final ...
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15 views

Is there a nontoxic chemical solution that expands and hardens under heat?

Is there a (nontoxic) chemical solution that expands and hardens under heat? The use case is to make an inexpensive Braille printer for a person with visual impairment. I want to be able to fill a ...
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26 views

Hot-side and Cold-side rechargeable chemical compound

I am wondering if such a chemical/material exists which, upon triggering, becomes cold on one side and hot on the other in which after all the chemical bonds are broken/built (however it would work), ...
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37 views

Endothermic Reaction with Specific Details

I need some information for a book I'm writing. Let's say you're in a confined space, about 8 feet by 8 feet. The area is being heated externally slowly (a few degrees a minute) to about 3,100 ...
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1answer
47 views

Does a Frying Pan Use Radiation?

I know this is a fairly basic question, however I am unsure. I have a project to prove that the colour black absorbs more light than the colour white in a creative way. Our first idea was to time a ...
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1answer
49 views

Why are molecular reactions endo- or exo-thermic?

It seems strange to me that chemical reactions should be exothermic, meaning the molecules move faster after the reaction. Normally, in physics when two moving objects collide and stick together, ...
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22 views

Entropy and Heat Capacity Trend in water

It is my understanding that entropy and heat capacity essentially measure the same thing. Since entropy is the ratio of heat (translational, rotational, vibrational movement) to temperature ...
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1answer
26 views

What is the chemistry behind heat produced when blood is bleached?

When I discard blood (20-40 mL) in a beaker containing bleach (400mL), I can feel that heat is produced in the beaker. What is the chemistry behind it? Will heat be produced due to Lysis of haem ...
3
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41 views

Theoretical temperature change in lime hydration

Calcium oxide (quicklime) and water have an exothermic reaction $\ce{CaO + H2O \rightarrow Ca(OH)_2} \quad \quad \Delta H^{\circ}_f=-65.3 \; \mathrm{kJ \cdot mol^{-1}}$ Assume that I have 1 kg of ...
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What is the difference between enthalpy (H) and heat (q)?

It seems that in some cases it's the same (that is, $\Delta Q_p=\Delta H$) yet in others they differ. For example, \begin{align} \ce{2H2(g) + O2(g) &->2H2O(l)} & \Delta H &= ...
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25 views

What is the latent heat of fusion of clay? [closed]

A simple question. I've looked around extensively but I couldn't find it so far.
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18 views

Would burning charcoal on galvanized mesh cause harmful fumes?

I can make a charcoal grate out of chicken wire - but the choice of easily obtainable materials seems to be between galvanized and PVC coated wire. I will do a burn off prior to cooking anything, but ...
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2answers
94 views

(P1,T1) -> to (P2,T2) then what will be the change in enthalpy for ideal gas?

I need to prove that it is equal to the integral of $C_pdT$ from $T_1$ to $T_2$. But should not be the case only when the pressure is constant?
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26 views

Problems with calorimetry

So, I just learned about calorimetry and am doing an equation to find the amount of heat released when carbon reacts with hydrogen to form methane. The equation I am using is $$ΔH=smΔt$$ I have m and ...
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43 views

How to calculate enthalpy change of neutralisation - what mass?

How to calculate enthalpy change of neutralisation - what mass? I made an experiment where I reacted 100ml HCL 2M with 100ml NaOH 2M in 1300ml Water, and got a temperature change dT. My question is ...
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53 views

Which is the specific heat of human body?

I'm studying about heat transfer and I wanted to know if there exists a specific heat of the human body or how one studies the human body's heat transfer.
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174 views

Heat transfer of sodium sulfate decahydrate assuming complete reaction [closed]

To make use of ionic hydrates for storing solar energy you place 136 kg of sodium sulfate decahydrate on your house roof. Assuming complete reaction and 100% efficiency of heat transfer, how much heat ...
0
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1answer
149 views

What temperature is required to burn graphite?

I tried to burn a bunch of 8B pencil lead in a gas flame the other day. None of it actually caught fire, but being made of carbon (in the form of graphite) should cause it to burn, as graphite is ...
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0answers
37 views

Why are hydrogenation reactions exothermic?

I learnt that all reactions that yield hydrogen are endothermic (such has reforming) and reactions, that use up hydrogen, are exothermic (FCC cracking, hydrogenation, etc.). But why is this so? I know ...
3
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71 views

Resultant temperature of mixture

**Question: ** There are 2 flasks of equal volume, connected by a narrow tube of negligible volume, filled with nitrogen gas. When both are immersed in boiling water, the gas pressure inside the ...
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1answer
57 views

Positive vs. negative heat of solution confusion

Given that I have absolutely zero formal (or informal) education in chemistry (sorry about that), I'm struggling to get my head around what appears to be repeated confusions of the term "heat of ...
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1answer
55 views

What is the meaning when it is said “Temperature of an Oxyacetylene Torch is 3500 degrees Celsius”?

I don't think flame is anything but the product at that temperature but I am not sure. What exactly is flame? And I think the correct statement should be that the exothermic reaction here produces ...
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0answers
21 views

Estimate inflammability of ABS?

I am studying some electrical components and particularly Raspberry Pi 2 official cases. Their manufacturer says that they consists of ABS (Acrylonitrile butadiene styrene) when I ask if their ...
2
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1answer
106 views

Heat of combustion of stereoisomers of 1-tert-butyl-2,4-dimethylcyclohexane

Which of the compounds below has the smallest heat of combustion? I know that the heat of combustion is indirectly proportional to the stability of a molecule. And here both $\ce{CH3}$ and ...
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1answer
137 views

Calculating Final Temperature and Volume of Adiabatic Expansion

A $\mathrm{5.00\ L}$ sample of $\ce{CO2}$ at $800 \ \mathrm{kPa}$ underwent a one-step (irreversible) adiabatic expansion against a constant external pressure of $100\ \mathrm{kPa}$. The initial ...
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1answer
90 views

Calculating entropy change of surroundings

I have seen many similar questions but have not found my answer. Why do we use the actual heat involved in the process to calculate entropy change of surrounding? The only answer I can think of is ...
3
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1answer
48 views

Product of lead and tin alloying

It is common knowledge that tin melts at $449.5~\rm^{\circ}F$ and Lead at $621.5\rm~^\circ F$, and that when these are melted together you simply have an alloy. What happens, or what product occurs, ...
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69 views

Hess' Law, Finding Heat of Solution

I am taking an online Physical Science 20 course and my teacher enjoys throwing labs on me before explaining the actual unit. I am given these two following reactions: ...
6
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1answer
270 views

How to calculate the heat released when Sodium Hydroxide is dissolved in Hydrochloric acid solution?

I need to understand how to calculate the heat released when sodium hydroxide is dissolved in hydrochloric acid solution. Here is the data I gathered from a lab experiment: $50\ \mathrm{mL}$ of ...
4
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2answers
67 views

How can the thermal conductivity of a binary gas mixture be estimated?

Recently, I am seeking for a simple but relatively accurate method to estimate the thermal conductivity of a binary gas mixture, say ethanol vapor + nitrogen. I assume the mixture as ideal gas. The ...
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0answers
36 views

Heat capacity during state change

I read that the heat capacity of water when it is at 100 °C or 0 °C is infinite because all the heat given to it will not be used to increase temperature but to change the state. I am unable to ...
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430 views

Does Gibbs free energy of formation always equal zero for elements in standard state?

I was looking through the appendix in my chemistry textbook when I noticed that every compound that had a $\Delta H_f$ of zero also had a $\Delta G_f$ of zero. So of course the compounds that have a ...
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1answer
33 views

Heating paper to a yellowish smoke

I put some papers into a biscuit tin and put it over fire and baked it. Then I made a small hole at the top and saw yellowish smoke coming out. Any idea what the smoke could be?
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1answer
76 views

Why can mercury oxide be decomposed into mercury and oxygen upon heating?

As I am a grade 9 student, please use simple English that does not involve many technical words in Chemistry. Thank you. I have learnt from my teachers' handout that physical methods of separation ...
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1answer
107 views

Do I need to include lattice energy when calculating the energy required to vaporize NaCl?

I understand that the lattice energy is the energy released when a crystal forms and that's the reason it takes the negative sign. But do we need to add this energy again when we are trying to ...
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1answer
67 views

Difference between thermodynamic terms heat and enthalphy [closed]

What is the difference between heat and enthalphy?
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2answers
43 views

Which phase is more efficient for temperature changes?

In the case of attempting to heat and cool down an object of different states, if you in some case managed to achieve the same temperature of a solid, liquid and gas what state would scientifically ...
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0answers
24 views

Entropy change of surroundings

The entropy change of a system is given by $dS=\frac{dq_{rev}}{T}$, which at constant temperature is $\Delta S=\frac{q_{rev}}{T}$. I also learned that the entropy change of the surroundings is $\Delta ...
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1answer
85 views

Irreversible process (Isothermal and Adiabatic)

How exactly would we define an irreversible change for an isothermal process? Why can we say what the external pressure will remain constant? Please give an example. Also, why can we not define both ...
0
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1answer
94 views

Difference between calcination and pyrolysis

What is the difference between calcination and pyrolysis? I have polymeric materials in mind specifically I understand they both involve heat treatment but each under a different type of atmosphere, ...
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1answer
59 views

Problem on determining the Calorimeter Constant from its heat capacity

A bomb calorimeter contains $600\;\mathrm{mL}$ of water. The calorimeter is calibrated electrically. The heat capacity of the calorimeter is $785\;\mathrm{J\,K^{-1}}$. The calorimeter ...
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24 views

Electrode/solution interface : What's the difference between the electrochemical Peltier heat and the heat caused from the overpotential?

In principle heat effects caused by the passage of an electric current might arise from: electronic peltier effect at the junction of electrode/solution level, Joule effect due to solution resistance, ...
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1answer
25 views

Spectroscopy and Excitation of Electrons

As metals are heated, they glow white and then blue. How might you explain this change in color as the temperature of the metal is increased? My answer consist of the idea that with increased thermal ...
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1answer
263 views

Calculate the mass of butane gas that would be needed to heat 724 cm³ of water from an initial temperature of 7.44 °C to 50.7 °C

The thermochemical equation for the combustion of butane is: $$\ce{2C4H10(g) + 13O2(g) -> 8CO2(g) + 10H2O(l)} , \quad\Delta H = -5748 \ \mathrm{kJ\cdot mol^{−1}}$$ So far, I've calculated the heat ...
0
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1answer
80 views

Calculate the amount of energy released when 500 cm³ of methane gas at STP reacts with excess air according to the equation:

$$\ce{CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)} \qquad \Delta H = -890\ \mathrm{kJ\ mol^{−1}}$$ I am not totally sure how to work this out. What I did, though, was: $\ce{CH4}$ $M = 16\ ...
2
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2answers
221 views

Minimum amount of water in pressure cooker

When cooking I would like to know the minimum amount of water I can add to my 6.2 L pressure cooker, worst case, so without any food. At second ring cooking the pressure is 0.8 bar. I assume I need ...
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2k views

Burns from boiling water and steam

Why is a burn to the skin caused by steam more serious than a burn caused by the same amount of boiling water at the same temperature? The temperature is the same, which implies that the kinetic ...
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175 views

Bond Energy Calculation

Dichlorine monoxide (which has the skeleton $\ce{Cl‐O‐Cl}$) is an unstable molecule and explodes readily to form chlorine gas and oxygen gas. The heat of the reaction $\Delta ...