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.

learn more… | top users | synonyms

1
vote
1answer
16 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 ...
0
votes
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 ...
3
votes
2answers
49 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 ...
0
votes
1answer
38 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 ...
0
votes
3answers
69 views

how can decreasing in temperature indicates 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 ...
0
votes
0answers
15 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.
0
votes
0answers
6 views

What is the heat of dissolution of sodium acetate trihydate?

Is the reaction endothermic since its crystallization is exothermic?
4
votes
1answer
27 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 ...
2
votes
1answer
276 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.
1
vote
0answers
24 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
votes
0answers
33 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
votes
1answer
34 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 ...
11
votes
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
48 views

Specific heat question?

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
votes
1answer
46 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
votes
1answer
71 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
votes
2answers
67 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 ...
0
votes
0answers
17 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? ...
1
vote
0answers
18 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
votes
3answers
97 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 ...
3
votes
0answers
47 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
votes
1answer
33 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 ...
0
votes
0answers
84 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
votes
2answers
148 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
votes
1answer
148 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 ...
-7
votes
1answer
74 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 ...
1
vote
1answer
33 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) ...
3
votes
1answer
1k 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 ...
0
votes
1answer
55 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
votes
2answers
95 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
votes
1answer
57 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)
1
vote
1answer
24 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 ...
0
votes
1answer
38 views

Can we define a new unit instead of specific heat that is constant with temperature rise?

Specific heat plays an important role in calculating energy and thus, heat, enthalpy and etc. But as I sighted the definition for calorie, I was surprised. A calorie is the amount of heat needed ...
-2
votes
2answers
70 views

When will the mass of the reactant increase while being heated up?

There is some kind of system which measures the mass of an unknown solid substance as it heats up, of course for the elemental analysis of the very substance. (didn't really find a good name for that ...
0
votes
2answers
47 views

What is the specific heat of copper through its phases?

Specific heat is the amount of heat required to change the temperature of 1 gram of a substance by 1 Celsius. For instance, the specific heat of water in the solid phase is 2.059 J/gC and 4.184 J/gC ...
0
votes
0answers
13 views

How does refrigeration fluid temperature affect reaction efficiency in a plug flow reactor?

This question appeared in some sample exam problems, and I can't seem to figure it out. Some preliminary information: Reaction: Exothermic, irreversible, gaseous phase Reactor: Refrigerated, ...
0
votes
0answers
9 views

Are the native starch's structure and properties different from retrograded starch?

Starch gelatinization occurs when native starch is being expose to heat and water. Gelatinized starch then can be retrograded under cool temperature. But the structure and properties of retrograded ...
1
vote
1answer
142 views

How much heat is needed to break CO2 down to CO?

I have found that because the oxygen is double bonded to carbon, it takes about $\mathrm{1500\ ^\circ C}$ to break it down from $\ce{CO2}$ to $\ce{C}$ and $\ce{O}$. But, I am curious, would it take ...
1
vote
1answer
80 views

Denaturing of Proteins and Nucleic Acids - Effect of Temperature (Heating VS Cooling)

Heating a protein/nucleic acid will disrupt inter-molecular and intra-molecular forces in the tertiary structure. It will also interfere with the shape of the active site if the protein. Does this ...
3
votes
0answers
48 views

Calcium chloride + starch desiccant packs inside PPE for ebola workers?

(First question on stackexchange, apologies for any faux pas) Ebola workers get drenched in sweat while working inside their personal protective equipment. There's a discussion happening over on ...
4
votes
1answer
66 views

why does a glass tube show white bands after being heated with a torch?

When I use a torch to split a glass tube, there's always a hazy white band which appears. Does anyone know what the cause of this is? (FYI, it was a hydrogen-oxygen torch. The glass is fused quartz ...
2
votes
1answer
37 views

Is there a heat capacity of an object when it is melting?

Is there a heat capacity of an object when it is melting? I'm questioning it since the temperature doesn't change during phase transitions and the units of heat capacity is Joules/Kelvin.
0
votes
1answer
186 views

Finding the equilibrium temperature between two substances in a constant pressure calorimeter

I need to find the temperature two things equilibrate to in a constant pressure calorimeter given only their specific heats, masses, and starting temps. The only thing I know for specific heat is ...
7
votes
2answers
877 views

Heats of combustion and stability of rings

Can anyone explain why? If you think about it, without having the data of the heat of combustion of each type of bond, you can't really answer this question. I know that cyclopropane has a higher ...
4
votes
2answers
557 views

What happens if you autoclave HEPES?

Many molecular biology protocols advice against sterilizing HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) solutions by autoclave. Supposedly, HEPES is heat labile, and the high ...
8
votes
1answer
99 views

What chemicals are used in receipt paper?

Most "invisible inks" turn brown when heated and they take a while to transform. I would like to make (or obtain) an "ink" that responds to the heat of an iron and permanently turns black or a ...
2
votes
1answer
377 views

The difference between heat of reaction at constant pressure and that at constant volume

If supposing the kp value of a reaction is 10 Atm at 300K and 4atm at 400K. Then how can we say that the difference between the heat of reaction at constant pressure and that at constant volume is RT ...
6
votes
2answers
1k views

How much does water expand when heated, and does salt affect that?

For this question, assume all things not mentioned are perfectly controlled, all at 14.7lbs of atmospheric pressure, and water is 100% pure of anything not mentioned, with no dissolved air. Given a ...
1
vote
1answer
53 views

Why does lactulose turn dark?

Why does the standard 10gm/15ml lactulose solution turn dark when exposed to heat above 30 degrees Celsius? This is probably a simple question. It is funny that the warnings/important information on ...
1
vote
2answers
546 views

How can I find the heat that will be released in kJ per gram for the reaction of Al with Fe2O3?

Find the heat that will be released in kJ per gram when aluminium ($\ce{Al}$) reacts with $\ce{Fe2O3}$ as follows : $\ce{2Al(s) + Fe2O3(s) → Al2O3(s) + 2Fe(l)}$ the information given is: $\Delta H ...