Questions tagged [temperature]

A measure of the average kinetic energy of the particles in a sample of matter; may be expressed either in kelvin (symbol K) or in degree Celsius (symbol °C).

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Why does the Temperature Decrease?

This is from a calorimetry lab. $50\ \mathrm{ml}$ of acid and base were mixed. Why does the temperature keep decreasing after 1 minute and why isn't at a constant rate? Is it because heat is lost to ...
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At what temperature do complex hydrocarbons become ashes?

When heating a metal tube with polypropelene in it, i found that i still had brittle black foam and flakes in it even though it had been in a blue flame at around 500'C What happens to complex ...
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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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Predicting the spontaneity of non-isothermal reactions

We use free energy equations -- Helmholtz or Gibbs -- to predict whether or not a reaction is spontaneous. These equations depend on constant temperature. This forum post describes a scenario where ...
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Can I freeze water at 100 °C if I add 28 grams NaCl in 100 grams water?

Can I freeze water at 100 °C if I add 28 grams NaCl in 100 grams water at 20 °C? I found this diagram that says, if I have 28.05 wt% NaCl in water, then the equilibrium temperature between two phases ...
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What is the reason for mpemba effect? [duplicate]

Under some circumstances, warmer water can freeze faster than colder water.
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Why does superglue lose strength at high temperatures?

I'm not a chemist. When I superglue my fingers together, by accident, I put them under warm water to peel off the superglue. Why does superglue become less "sticky" at higher temperatures? Is it the ...
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Does freezing tights make them more durable?

Various blog posts and articles suggest that freezing a pair of tights will make them last longer. From a blog named Eclipsed Moon: Put your tights in the freezer. I thought that this was ...
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How do you find the change in internal energy (q+w)?

If a monoatomic ideal gas simultaneously expands against a constant external pressure and drops in temperature, how do you find the internal energy change? Known values are: $T_1$, $T_2$, $p_1$, $...
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How could I find the solubility of hydrocarbons such as iso- and n-Butane in liquid Methane?

I am trying to figure out the dissolution capacity of iso and normal butane in methane at very low temperatures (110K). This would allow me to make compositions that prevent freeze out of these ...
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Reversible and Irreversible adiabatic expansion

A $\mathrm{200.0\ m^3}$ balloon at $253.0\ \mathrm K$ ascends to a higher altitude. If the initial pressure inside the balloon is $325$ millibar, and it ascends to a latitude with a pressure of $7.45$ ...
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What equipment to use to make liquid oxygen?

I'd like to do some experiments with liquid oxygen but as a first step I'll have to make some. Unfortunately I don't have any experience designing cryogenic experiments. I'm thinking I'll cool gaseous ...
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How to calculate the boiling point of a solid substance?

Say that I have a solid substance; I know its density, mass, volume, melting point, specific heat, the pressure which it is under, and nothing else. (for now.) How do I find the heat at which it ...
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When can a molecule be considered freely rotating at room temperature?

This question sparked from a long discussion in chat about the nature of $\ce{H2O2}$ and whether that molecule can be considered to rotate around the $\ce{O-O}$ axis (and hence display axial chirality)...
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Le Chatelier's Principle: Temperature dependence in endothermic and exothermic (Chemical Equilbrium)

What effect does temperature have on endothermic and exothermic reversible reactions? (Please also mention the reason why it happens like this) And what do people mean by doing something like ...
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How is Negative Temperature Hotter than Infinite Temperature?

Recently I have read articles stating that negative Kelvin has been achieved. I was a bit speculative at first as I though how can you get cold than 0 Kelvin, but after doing some research it makes ...
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Effect of quantum tunnelling on chemical reactions at very low temperature [closed]

Can anybody give me a schematic representation of how quantum tunneling allows chemical reactions to occur at very low temperatures like in the interstellar medium.
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Is the absolute temperature concept 100% viable?

Maybe I'm wrong about it but I wanted to know whether the concept of absolute temperature is real or not. As every element behaves differently at a particular temperatures how could we assign a ...
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Container to supercool water

The internet is full of videos like this showing water bottles for drinking used to supercool water. These bottles, not unexpectedly, appear a bit finicky, since they have lots of edges to serve as ...
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Does the Maxwell-Boltzmann distribution apply to gases only?

The Maxwell-Boltzmann distribution can be used to determine the fraction of particles with sufficient energy to react. I know that the curve applies to gaseous reactants and would like to know whether ...
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What is the proper term for lines of constant volume and constant enthalpy on a thermodynamic diagram?

I know an isotherm is a line of constant temperature. Isobar is a constant pressure line. Isentrope is a line of constant entropy. But what do you call a line of constant volume? An Isochore? And ...
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How can I use sunlight to heat a RBF and reflux a reaction?

This may seem like a off topic question but I really need help on it. I am currently working on a polymerization reaction in which I'm breaking down plastic polymers into smaller molecules. However, ...
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Temperatures Below Absolute Zero [closed]

This seems like a farce... Quantum gas goes below absolute zero Ultracold atoms pave way for negative-Kelvin materials. by Zeeya Merali, Nature News 03 January 2013, DOI: 10.1038/nature.2013....
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Super-cooled liquids

I understand that it is possible to cool a liquid past its freezing point, and still maintain its liquid state because crystallisation would not happen in the absence of a seed crystal. My question, ...
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What is the explanation of the odd even effect in liquid crystals?

What is the most accepted theory for explaining the odd even effect in liquid crystals? Can anyone explain and refer the corresponding paper?
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Melting temperature vs Isotropisation temperature in liquid crystals

What is exactly the difference between these two? I think melting point is when the compound melts down to visually liquid state but actually LC state and latter is when polymer becomes completely ...
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Relation between Temperature and viscosity of Linseed Oil?

I have been trying to get a relationship formula to determine the viscosity of Linseed oil. I have Absolute viscosity of the oil at 33.1 Cp (Source: http://www.engineeringtoolbox.com/absolute-...
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Can I get an accurate temperature reading from a flask with a built-in thermometer well?

I recently purchased a flask with a built in thermometer well, but I have discovered that simply setting a rod thermometer in the well does not produce a very accurate reading. I was wondering if ...
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Target temperature for infused cooking oil

A little context: I make craft chili oils for friends and family. I use a two-step infusion process. First, I infuse the oil for flavor by simmering spices in the oil held around 250 degrees ...
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Equation for heat loss over distance?

Is there an equation to figure out what the temperature of an the area will be a certain distance from the heat source? For example, if I know there is a heat source at $0~\mathrm{m}$, and the ...
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50-90'C color changing chemical to use as warning marker for hot electronics?

I am testing electronics with many potentially unstable contacts, and I wish to monitor if they rise above 50 to 90 degrees Celsius, i.e. using carbon paper that would darken progressively from 50 to ...
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Do all gases occupy same volume at equal temperature and pressure conditions?

Why does one mole of all gases occupy 22.4 L at standard temperature and pressure? According to my thinking, it may be due to equal diffusion of all particles when at a particular temperature and ...
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What is the significance of 273.16 K?

Today, at my chemistry class, we were learning how to convert Celsius to Kelvin with exact values. I said we add 273.15 K to given Celsius but my colleague said we add 273.16 K. Yes, I did check on ...
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How can cooling gases do not change their physical states?

It is stated in my book "All gases condense to form liquids or solids before -273.15 degree Celsius is reached? could you explain this statement generally and my question in the title specifically?
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What is the CO2 content in the air in a compartment of air and water, as a function of temperature?

Update 31.12.2015: In a closed system of water and air, how does the concentration of CO2 change as a function of temperature, in the gas phase? What is the graph of carbon dioxide ($\ce{CO2}$) ...
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What is the equation that demonstrates the relationship between molar conductivity and temperature?

Can someone please help me find the equation that defines the relation between molar conductivity and temperature. I have found some information, but it was not really that much complete.
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Determining which hydrate of calcium chloride I have?

I have calcium chloride in the form of small (1-2 mm) round white pellets, originally bought at a home-brew shop. The packaging gives no indication what hydrate it is. Since each water molecule adds ~...
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heat capacity and thermal equilibrium

A $52\ \mathrm{g}$ piece of iron at $250\ \mathrm{^\circ C}$ is added to a mixture of $100\ \mathrm{g}$ of ice and $100\ \mathrm{g}$ of liquid water at thermal equilibrium $(0\ \mathrm{^\circ C})$. ...
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Why does the mixture's temperature change while phase transition?

Consider a mixture made up of alcohol and water at room temperature. If I freeze this mixture, why does it change its temperature during the phase change? I don't understand the difference between ...
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Can paper burn without oxygen or air?

If you put a paper inside an oven vacuum packed and go beyond $250~\mathrm{^\circ C}$, will it burn? There's no oxidizer. If not, what will happen?
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Calculate species concentration from first-order kinetic reactions

I am trying to determine the concentration of products from the kinetic reactions of wood pyrolysis. The kinetic scheme separates the wood into cellulose, hemicellulose, and lignin. For example, the ...
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Thermometer fluid is separated, defective?

I bought a thermometer from Cole-Parmer having kerosene as the fluid, and the fluid is broken up. The fluid in the bottom part goes up to about 10 °C even though it is 20 °C in the room, then there is ...
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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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Thermochromic pigment that changes at around 50 °C / 120 °F?

I wish to find a pigment that can indicate when a battery contact is getting too hot, and all the thermochromic pigments from hobby stores change color below body temperature, at 31 °C is the highest ...
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Temperature of an atom

I read somewhere that the temperature of an atom is not defined. The definition of temperature is only for larger systems. Why is this so?
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What determines humidity limit / dew point of the air? - Why can air only hold a certain amount of water?

From Wikipedia: The dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At ...
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What is an example of a very low temperature endothermic reaction?

Shakashiri describes the reaction of solid Ammonium Thiocyanate and solid Barium Hydroxide Octahydrate resulting in an endothermic reaction leading to subzero temperatures. I've performed this ...
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What causes the colour when conducting flame tests on solid salts?

The normal technique for flame tests is to dip a clean nichrome or platinum wire into a solution of the relevant salt, and observe the resulting flame colour when inserting the wire into a non-...
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Why does a liquids height in a Barometer depend linearly on pressure?

Here is a derivation I found relating the pressure P, gravity g, height h, and density $\rho$, of a liquid in a barometer $$ P=\frac{mg}{A}\\ V=Ah \\ P = \frac{mgh}{V}\\ \rho=\frac{m}{V}\\ P = \rho g ...
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What value of temperature does T represent in Gibbs Free Energy Equation?

Temperature before, or after reaction? Temperature change? Or what is it?