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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What is a kg.cal per gram, as a heat of combustion?

I see heats of combustion given in kg [dot] calories per gram molecular weight (Handbook of Chemistry and Physics, 1969-1970). I don't know how that makes sense, as I don't know what a kg cal might ...
13
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1answer
134 views

Why does milk overflow when boiled?

I was wondering that like whenever I boil milk I just have to keep standing in front of it to make sure that I don't waste any milk but then I was wondering like Why does it even overflow ? In case of ...
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44 views

How to calculate the specific heat

What is the specific heat of a 20 g substance that releases 979 J of heat when changing from 70 °C to 25 °C. I started out with the following equation: $c = \frac{Q}{m\Delta T}$ $Q = 979\ ...
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0answers
21 views

How the heat a large amount of water that is safe to use?

I would like to know how heat up a large amount of water ( assumption : 100 liter ) that people could use to take their bath and also it would not be dangerous even if they accidentally ingested it ? ...
4
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1answer
65 views

Difference between Superheated steam and Superheated water?

I'm working on a project (school level) and in it I'll be dealing with the pressure generated by water when superheated. I could understand the concept of superheated water but superheated steam is ...
5
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1answer
332 views

What happens if I make a hole in a container with superheated water?

Superheated water is achieved by heating water above 100 degree Celsius under high pressure. Now, suppose the temperature at which the water is getting heated is around 250 Celsius and sufficient ...
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4answers
282 views

What is the origin of the maximum in rotational heat capacity?

The graph of rotational heat capacity above shows a small maximum before approaching the equipartition value. What is the origin/physical explanation of this maximum?
3
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1answer
66 views

In order to solve for this equation for heat capacity, do I need to treat it as a system of equations?

For a lab, we took the temperature of 15ml of tap water, $q_{cool}$, then added 20ml of tap water warmed to 80 degrees Celsius, $q_{warm}$. We recorded a baseline temperature of 24.8, a temperature ...
6
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1answer
61 views

Do I understand why heat capacity is called 'heat *capacity*'?

The notion of heat capacity seemed a little odd to me. I thought that the word 'capacity' could be throwing me off. Do I understand the notion correctly? I take the word 'capacity' to express, ...
6
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49 views

Scission of carbon dioxide bonds using electric arc

I've done my research on this so I've seen the questions asking about the same premise without using plants. Basically, this is a thought experiment I came up with. Whether or not I perform it ...
6
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2answers
117 views

Why is a tin can that appears like galvanised steel rusting?

I bought a canned pineapple and finished the content. The part of the can that is in contact with the liquid appears like galvanized steel (crystalline surface or spangles sort of appearance), while ...
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1answer
87 views

How to figure out which two solutions will emit largest heat when they are mixed in same volumes?

How can I figure out which two solutions will emit the largest heat, when they are mixed in same volumes? Then let's assume that there is are five pairs of solutions given: \begin{align} \ce{2NaOH + ...
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35 views

Which of these compounds does not liberate heat when water is added to it?

Which of these compounds does not liberate heat when water is added to it: $\ce{KNO_3}$, $\ce{NaOH}$, $\ce{CaO}$, $\ce{H_2SO_4}$, $\ce{Na}$. I know from experience that dropping sodium tablets into ...
2
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1answer
38 views

Chemical formula and heat

In my Physical Science class, we are learning about chemical formulas and how to balance them. I balanced this equation: $\ce{Fe2O3 + Al -> Fe + Al2O3}$ One of the other students ...
6
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2answers
99 views

What is the difference between tempering and hardening metals and their end products?

I think I've heard hardening is when you dunk red-hot metal into cold water, and tempering is when you take that hardened metal, heat it slightly, and then let it cool slowly. However what is the ...
2
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1answer
167 views

Exo- or endothermic? Clarification required regarding a few cases

Are the following processes exothermic or endothermic? a) When solid $KBr$ is dissolved in water, the solution gets colder. b) Natural gas ($CH_4$) is burned in a surface. c) When concentrated ...
2
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1answer
31 views

Ratio between heat tranfer coefficient and thermal conductivity

Consider the Robin boundary condition for the diffusion/heat equation $\mathrm{u_t=a(t)u_{xx}+f(x,t)}$: $$\mathrm{-k(t)u_x(0,t)=h(t)u(0,t)}$$ or $$\mathrm{u_x(0,t)+\frac{h(t)}{k(t)}u(0,t)=0}$$ ...
6
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138 views

How can I measure the internal temperature of a solid metal?

I’m heating up several metal blocks as part of an experiment to determine their specific heat capacities. In a nutshell, I’m heating the blocks of known mass to 100 °C, then adding them to an ...
2
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1answer
64 views

Heat Capacity temperature dependence and Gibbs energy

I got this problem in school as a tool to get ready for International Chemistry Olympiad, but I have some problems with this challenge. So, the problem is to calculate as precise as possible the Gibbs ...
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0answers
15 views

Why is it that reactions that cause an increase of temperature are exothermic? [duplicate]

I've been taught that if you have two aqueous reactants that react together and produce heat it is exothermic. Shouldn't that be endothermic? Did my professor misspeak? If it's gaining heat, that ...
2
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2answers
86 views

Thermochemistry: forms of energy & pressure

I've been in a few classes now that teach about energy, and I feel they're always so bad. There is always such a rush to start using equations to get problems solved, and I often feel I don't have an ...
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1answer
106 views

Amount of Energy Needed for Boiling a Litre of Water [closed]

What is the amount of energy (J or Wh) needed to boil one litre of tap-water in a regular kettle starting at room temperature (20°C)? The calculation itself assuming ideal and standard prerequisites ...
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150 views

How can decreasing in temperature indicate an endothermic reaction?

I’m really wondering how can decreasing the temperature refer to an endothermic reaction. I faced this when I was calculating the heat of a reaction Q in a constant-pressure calorimeter. What I ...
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19 views

Are there a few nontoxic chemicals that when rubbed together or even mixed create heat?

Are there a few nontoxic chemicals that when rubbed together or even mixed create heat? Looking for dry elements preferably that could be mixed.
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25 views

What is the heat of dissolution of sodium acetate trihydate?

Is the reaction endothermic since its crystallization is exothermic?
4
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1answer
37 views

Pre heat coal before burning

So I was wondering if pre-heating coal will improve the efficiency of a steam boiler. I did find that intake air pre-heater and water pre-heater do increase efficiency, but I could not find anything ...
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1answer
558 views

Why is the specific heat of water high?

How is the specific heat of water so high? I was reading the hyperphysics article on it but could not understand it properly.
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25 views

How do things heat one another? [duplicate]

For example, how does a gas stove heat a metal pot? A combustion reaction between the gas and the air takes place, and this releases energy due to new chemical bonds being formed. Do the atoms in ...
2
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0answers
45 views

How are pressure vessels heated?

I'm working on a project in which I'll be dealing with pressure vessels. As of now I've drawn/conceptualized everything on theory basis. The diagrams are made on the basis of theory, but then I came ...
3
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1answer
78 views

What is the temperature of heat generated from LPG gas?

I'm working on a project and I require around 300-400 degree Celsius of temperature. As of now I'm taking the normal LPG gas that is available in our house for cooking purposes for my project, but I'm ...
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7answers
5k views

How can 30 ml of water be heated in less than 10 seconds?

How is it possible to heat a tiny amount (30 ml)[1] of water to a high enough temperature to make a coffee, in less than 10 seconds and possibly instantly? Most heaters that I know of heat water ...
2
votes
1answer
76 views

Why did they provide the value for the enthalpy change of fusion?

The metal gallium melts when held in the hand; its melting point is 29.76 degrees C. How much energy as heat is removed from the hand when 5.00 grams of gallium initially at 20.0 degrees C melts? The ...
2
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1answer
59 views

Why does lithium move on the surface of water during the reaction?

If someone asks me to number the most notable "textbook experiments" I would definitely name "the comparison of the reactions of alkali metals with water" among the most favorites. We just happened ...
2
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1answer
155 views

Why and how does lycopene absorbance increase with heating?

Lycopene, which is a carotenoid and a phytochemical is the main reason for why tomatoes are radio-protective. Source 1 . Source 2 Let's cut to the chase: I was wondering if this claim of The ...
2
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2answers
134 views

Heat energy of phosphoric acid evaporation

Looking at a system in which phosphoric acid is concentrated in an evaporator which uses a constant recycle stream with a heat exchanger in this stream to heat the acid so that water evaporates out of ...
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32 views

Can N-Zorbit absorb wine and then dried while keeping the same alcohol level?

I'm trying to see if you could use the modified starch N-Zorbit, a maltodextrin, to absorb a low sugar wine (pinot noir for example) and then dry it while keeping the alcohol levels the same or close? ...
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26 views

solvent interaction with thermal paper

If you place a piece of paper that prints via a laser eg, fax paper or some receipts, on top of a piece of normal paper you have drawn on with a Bic Marking 2300 permanent marker, the image transfers ...
2
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3answers
139 views

Why is it obligatory to cool down the container of a sample to measure its mass in a lab?

We were doing an experiment about hydrated crystals and more precisely how to determine $n$ in $\ce{CuSO4.nH2O}$. After we heated the crucible we were to cool it down using a Desiccator. Then this ...
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0answers
69 views

How does heat and/or boiling remove vitamin C?

The www is full of crackpot claims about how various food treatments alter their nutrition content and it makes finding actual science very difficult. I am specifically interested in the vitamin C ...
3
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1answer
37 views

Why might my limelight experiment have failed and how can I improve it?

I was teaching the lime cycle to some children yesterday. I had a limestone chip (about 10g) held at the tip of a blue bunsen flame for several minutes. It decomposed and disintegrated but only glowed ...
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103 views

What compound can give off heat when it comes in contact with ice?

What compound is able to produce heat when it comes in contact with ice? The compound has to be able to produce heat multiple times. I was thinking of a compound that is similar to Calcium Chloride. ...
0
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2answers
380 views

How does this method of calculating the water equivalent of a calorimeter work?

I am doing a AP Chemistry lab in which we determine the heat capacity of a calorimeter (a concept that seems like it should depend on a lot more than just the calorimeter.) We have to calorimeters ...
4
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1answer
166 views

Is it possible to make broad spectrum light absorbing paint?

Is there such a paint / pigment that absorbs most wavelengths of light (beyond the visible light range) that can be used for solar heat generating applications? If not, would it be possible to make ...
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1answer
97 views

Why does the freezing point of a sample gas occur at a certain temperature? [closed]

From "North Carolina Measures of Student Learning: NC’s Common Exams Chemistry" (Source, Number 20): The graph below shows a cooling curve for a sample of gas that is uniformly cooled from ...
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1answer
50 views

Is the reaction exothermic or endothermic?

Is the following reaction endothermic or exothermic? Please note the following: When heat is removed from the system, the solution turns bright red (the reaction shifts towards the reactants side) ...
6
votes
1answer
5k views

What is “heating under reflux”?

When dealing with organic reactions, heating under reflux is often required, such as the oxidation of Toluene using acidified $\ce{KMnO4}$ and dilute $\ce{H2SO4}$ to Benzoic acid($\ce{C6H6O2})$ What ...
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1answer
89 views

Why do heavier elements have smaller specific heat values.

In the periodic table the trend is that as the mass of each element increase's the specific heat tends to go down. This seems to be counter-intuitive because if I am not mistaken as mass increase's ...
2
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2answers
323 views

Which formula is correct for calculating the heat of dissolution?

I want to calculate the energy change when a solute is dissolved in water. I know that I can achieve this by using the equation $q=mc \Delta T$. My question is does the mass ($m$) change with the ...
2
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2answers
128 views

Nuclear power: what material is the control rod made from?

My question: What type of material is used in the control rod of a nuclear reactor? (Nuclear power plant)
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1answer
28 views

What physical properties are manifested when an electron leaves Na and moves to Cl to form an ionic bond?

When an ionic bond is formed between Na and Cl, the lone electron in Sodium's outer shell leaves, and completes Chlorines outer shell. Are there any physical characteristics that I can use as an ...