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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Is this endo or exothermic?

$$\ce{4Fe + 3O2 -> 2Fe2O3(s) + 1625~$\mathrm{kJ}$}$$ This should be endothermic because the energy is in the product. However, if the equation is viewed from the perspective of the reactant, it ...
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What are the physico-chemical processes at play in ironing of clothes?

The process of ironing of clothes removes (to a large extend) the wrinkles that where introduced in the clothes while drying. Obviously this has to be some physico-chemical process that is initiated/...
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1answer
259 views

Change in pressure or volume of molten salt

I am doing a project in which I fill a cylinder with a volume of $636cm^2$ (made of stainless steel) with molten salt: 60% Sodium Nitrate ($NaNO_3$) and 40% Potassium Nitrate($KNO_3$). The container ...
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3answers
816 views

Safety concerns - Heating PMMA (acrylic glass) and fluorinated polymers

I have some plastic optical fiber, which consists of a thin core of PMMA (polymethyl methacrylate), covered by a fluorinated polymer. I would like to heat a bundle of these fibers to ~130 degrees, in ...
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1answer
90 views

Is there a way to get hot water without altering plumbing or electrical wiring too much?

Is there a way (other than collecting water and heating it on the stove ) to get hot/warm water from the tap without having to alter existing plumbing or electrical wiring ? Perhaps use a chemical ...
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1answer
15k views

How do you calculate the total heat capacity of a reaction

I need help with this one homework question: I am combining $100\,\text{mL}$ of $0.5~\text{M}~\ce{HCl}$ and $100~\text{mL}$ of $0.5~\text{M}~\ce{NaOH}$ to obtain $200~\text{mL}$ of $0.25~\text{M}~\...
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2answers
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How to determine the vapor pressure of a glycerine and propylene glycol mixture?

I am looking to calculate the minimum heat needed to create vapor from a specific mixture. I have a mixture of 60 % $\ce{C3H8O3}$ (glycerine) and 40 % $\ce{C3H8O2} $ (propylene glycol, propane-1,2-...
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1answer
4k views

Why does glass shatter when heat is applied to it?

When I poured hot tea into a cup, the cup shattered after about three seconds. The cup was made of glass. It was pretty thin. How did the glass and the tea react in terms of chemicals. This is a bit ...
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1answer
1k views

Finding the final temperature

If $125$ Calories of heat is applied to $60.0\text{g}$ piece of copper at $21.0^\circ\text{C}$, what will the final temperature be? The specific head of copper is $0.0920 \text{ cal/gC}$. All I have ...
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2answers
12k views

Baking Soda + Oil at high temps

My mom while making Potato chips put some Baking Soda in Oil with it. Just curious to know, it was first time Baking Soda in Oil at that high temperature. Is it safe to eat? Answer ASAP before my ...
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Are all PP(Polypropylene), i.e. resin code 5 plastics, safe for microwave and steaming?

If a plastic is marked PP as in Polypropylene (i.e. resin code 5), is it automatically safe for steaming and microwaving, such that it wouldn't leach chemicals into the food(besides not melting)?
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Heat produced when magnesium is reacted with acid

Calculate the heat produced when a strip of $\ce{Mg}$ metal with a mass of $\pu{0.0801 g}$ is reacted with $\pu{50.0 ml}$ of $\pu{1.0 M}$ $\ce{HCl}$ to raise the temperature of the water by $\pu{7.6 °...
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2answers
5k views

How well (or poorly) does natural leather insulate?

What is the general thermal conductivity of animal skin leather? I understand there are many different animal's skins (cow, sheep, buffalo, deer, pig), but in general, does natural leather insulate ...
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3k views

Is tea powder better dissolved when put in hot water?

I usually make tea by adding two spoons of tea powder to water at room temp. and start to heat it. My friend said it will be better to add the powder once the water starts boiling. She said that it ...
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3answers
65k views

Why is the enthalpy change not zero in an adiabatic process?

Which of the following must be true for adiabatic processes? $C_V = C_p$ $\Delta H = 0$ $\Delta U = 0$ $\Delta S = 0$ $q = 0$ (Source: Chemistry GRE) The answer is $q = 0$. From ...
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1answer
9k views

Is it customary to express heat loss as a negative number?

In my chemistry class, we had a problem akin to the following: If an object with mass bla and specific heat bla is placed into a bla g calorimeter with an initial temperature of bla and a specific ...
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1answer
696 views

How do I find the thermal effect of this reaction?

I have graphite turning into diamond.I need to find the thermal effect of this reaction.How would one write that?I'm not sure how to proceed here.The teacher told us to use oxygen?
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1answer
7k views

How much heat is required to dehydrate a hydrate?

If I have a hydrate, such as copper (II) sulfate pentahydrate, $\ce{CuSO_4 \cdot 5H_2O}$, what is the amount of heat to required to dehydrate it? I assume that it is equal to or greater than the ...
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2answers
1k views

Why is water evaporation not more commonly used to cool buildings [closed]

Water has a very high heat of vaporization (2260 kJ per kg). Why not just gradually sprinkle water on your roof to keep the building cool in opposed to using air conditioners? It wouldn't take much ...
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0answers
183 views

energy efficiency, transformation from chemical to thermal energy, for district heating plants

If I have a system in which I introduce $\mathrm{100~e.u.F}$ (energy units) derived from chemical energy (i.e. fuel) and generate thermal energy to heat water what are e.u. absorbed by water? I.e. the ...
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9answers
478k views

Why does ice water get colder when salt is added?

It is well known that when you add salt to ice, the ice not only melts but will actually get colder. From chemistry books, I've learned that salt will lower the freezing point of water. But I’m a ...
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1answer
2k views

What is the heat energy required to perform electrolysis equivalent?

The question may be off-topic here. If my concept is flawed, please poke me in the rib (+: Sources on the internet indicate a minimum 1.2Volts is adequate for electrolysis of water; nominally 6V. ...
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1answer
2k views

Lower Heating value calculation from chemcial combustion equation of Butane

QUESTION Butene, C4H8 is burned in an engine with a fuel-rich air-fuel ratio. Dry analysis of the exhaust gives the following volume percents: $\ce{CO2} = 14.95%$, $\ce{O2} = 0%$...
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4answers
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Why won't water freeze if you put ice in it, despite ice being frozen?

Just now I got some room temperature water and added some ice to cool it, and it just came to me, like the scientist I wish I was ... why doesn't frozen (freezing point) ice added to higher ...
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3answers
10k views

Can you heat water with additives?

I have been curious about this question for a while. If you want to warm up a large amount of water, is it feasible to do this by adding a substance that has an exothermic reaction with the water? ...
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4answers
77k views

How do I chill water without a refrigerator?

How can we chill water in a plastic bottle without a freezer or refrigerator? Scenario: I'm in the office and I have two plastic bottles of water (brought from home). I'm in the office for 3 to 4 ...
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1answer
744 views

Specific latent heat of fusion of a noble gas

Could someone explain to me where the additional energy goes when applied to an object in the state of melting (such as water) so that the temperature of the object does not increase, and could ...
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2answers
181 views

Egg-Detection in Pastries: An Analysis in Heat-Alterated Molecule Identification

I would like to know if anybody here knows of a method to detect the presence of ovalbumin--or any unique, egg-related molecule, in a baked good. Here I am anticipating that the "unique egg-related ...
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2answers
2k views

Better understanding the pyrolysis reaction

I'm no chemist, but much of my work revolves around biochar. I've always understood it with the following rough approximation: $$ \ce{CH2O (dry plant matter) + heat -> black carbon + H2 + CO + ...
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1answer
2k views

Is the activation barrier of a reaction related to the free energy or heat of formation of its reactants?

The energy barrier for activation appears in the derivation of a bimolecular reaction through collision or transition state theory, but it seems that from looking at diagram such as this one it seems ...
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1answer
578 views

Why do we need to incubate this system for 18 hours at 60 degrees Celsius?

I am conducting a bio-chemistry related experiment and I have been unable to understand a step which is commonly performed. The procedure that is confusing me is outlined in the supporting information,...
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1answer
125 views

What determines a substance's energy of activation with air?

Ice will melt when heat is applied; paper will catch fire. In trying to figure out why — what the difference is between things that melt and things that catch — I found "Burn, Char, Melt" by Roberto ...
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1answer
10k views

Enthalpy Calculations, Heat of Formation/Combustion

I just don't understand how to do these and would really appreciate your help. 1) Ammonium dichromate decomposes in a reaction when heated. Calculate the heat transferred for the decomposition of 53....
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1answer
23k views

Why does a substance with an endothermic heat of solution dissolve?

How does a substance with an endothermic heat of solution dissolve?
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5k views

Which materials/compounds expand in response to cold temperatures?

Which materials or compounds expand in response to cold temperatures? This material or compound should expand at a slow (but constant rate), from about 0–20 months when in the following temperature ...
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1answer
112k views

How do you calculate molar specific heat?

I know how to calculate the specific heat, but not molar specific heat. What is molar specific heat and how do you calculate it?
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1answer
643 views

Are there any nonflammable thermal insulators which can be made at home?

I am trying to build a homemade thermos. It needs to be able to conserve the heat in 125 ml of water for 15 minutes. However, unlike a normal thermos, it also needs to be able to be heated. What ...
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3answers
10k views

Chemical reactions with a room-scale cooling effect

Are there chemical reactions that could cool down an average sized room by a noticeable amount (say 5 °C)? I would like to investigate if it is possible to have a situation where I can mix 2 ...

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