Questions tagged [temperature]

It's the physical property that indicates the degree/intensity of heat present in a substance or an object. It can be expressed and measured according to various scales.

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148
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Why is my hand not burned by the air in an oven at 200 °C?

I have this problem from University Physics with Modern Physics (13th Edition): The inside of an oven is at a temperature of 200 °C (392 °F). You can put your hand in the oven without injury as ...
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Is temperature a Lorentz invariant in relativity?

If an observer starts moving at relativistic speeds will he observe the temperature of objects to change as compared to their rest temperatures? Suppose the rest temperature measured is $T$ and the ...
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Why doesn't water boil in the oven?

I put a pot of water in the oven at $\mathrm{500^\circ F}$ ($\mathrm{260^\circ C}$ , $\mathrm{533 K}$). Over time most of the water evaporated away but it never boiled. Why doesn't it boil?
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Why do spaceships heat up when entering earth but not when exiting?

Recently I read up on spacecrafts entering earth using a heat shield. However, when exiting the Earth's atmosphere, it does not heat up, so it does not need a heat shield at that point of time yet. ...
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Would a pin head heated to 15 million degrees Celsius kill everyone in a 1000 mile radius?

The YouTube video How Hot Can it Get? contains, at the 2:33 mark, the following claim: A pin head heated to 15 million degrees will kill everyone in a 1000 miles radius. On what basis can this ...
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Why don't miners get boiled to death at $4$ km deep?

The Mponeng Gold Mine is nearly $4$ km deep. It has the largest elevators in the world and is considered one of the most dangerous mines in the world. The geothermal gradient is $25$ degrees Celsius ...
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Why does hot water clean better than cold water?

I had a left over coffee cup this morning, and I tried to wash it out. I realized I always instinctively use hot water to clean things, as it seems to work better. A Google search showed that other ...
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Will a hole cut into a metal disk expand or shrink when the disc is heated?

Take a metal disc and cut a small, circular hole in the center. When you heat the whole thing, will the hole's diameter increase or decrease? and why? What will happen to the diameter of disc?
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Why does water stop boiling immediately after turning off the heat?

When I am heating water on a gas stove, it begins to boil after some time and bubbles of air can be seen escaping out. However, as soon as I increase the amount of heat in the stove, the rate of ...
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Why is there no absolute maximum temperature?

If temperature makes particles vibrate faster, and movement is limited by the speed of light, then I would assume that temperature must be limited as well. Why is there no limit?
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If I stood next to a piece of metal heated to a million degrees, but in a perfect vacuum, would I feel hot?

A friend of mine told me that if you were to stand beside plate of metal that is millions of degrees hot, inside a 100% vacuum, you would not feel its heat. Is this true? I understand the reasoning ...
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Could a candle theoretically melt iron?

The title question is rather illustrative. I suppose the real question would be: Is heat cumulative? Put back into an example: If I have a lit candle right beneath an iron bar, assuming the candle ...
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How does water evaporate if it doesn't boil?

When the sun is out after a rain, I can see what appears to be steam rising off a wooden bridge nearby. I'm pretty sure this is water turning into a gas. However, I thought water had to reach 100 ...
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What makes cheese so effective at absorbing microwaves?

Whenever I put a meal in the microwave which contains cheese, why does the cheese get hot before the rest of the meal is heated through?
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Why don't you get burned by the wood benches in a sauna?

When you go to the sauna you may sit in a room with 90°C+. If it is a "commercial" sauna it will be on for the whole day. How does it come that when you sit on the wood you don't get burned? I ...
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How long can you survive 1 million degrees?

I asked my Dad this once when I was about 14, and he said that no matter how short the amount of time you were exposed to such a great temperature, you would surely die. The conversation went ...
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Why has Earth's core not become solid?

The Earth is billions of years old, yet its core has not yet cooled down and become solid. Will this happen in the foreseeable future?
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How did my candle wax crawl up the sides of the jar?

I have an Ikea candle which has sat on my bookshelf in the sun for >5 years. Aside from an hour or two shortly after I bought the candle, I have not burned the candle regularly (in fact, the wick is ...
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Will a blanket warm you if you are underwater?

Suppose a man falls into very cold water and gets their foot stuck under a heavy rock. Fortunately, his head is above water and someone is able to call for help. The paramedics want to keep him warm ...
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Why does cold metal seem colder than cold air?

(I apologize for this elementary question. I don't know much about physics.) Let's say that I put a metal pot in the refrigerator for several hours. At this point, I guess, the pot and the air (in ...
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Why does pressure in a thermos increase after shaking up hot water and soap?

Whenever I wash my thermos, I put hot water and then some soap in; then I seal the one end with my hand or use the lid. After shaking it up, if I slowly remove the lid or my hand, it expels a little ...
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Could I survive at (or near) absolute zero with a very, very, very thick sweater?

Imagine I'm in an infinitely large vacuum and have a special apparatus built into my body that allows me to breath, eat, pee/poo, etc. and never age. The vacuum is similar to deep space and has no ...
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Why doesn't increasing the temperature of something like wood or paper set them on fire?

Imagine we have paper book. If we put this into a pan and increase its temperature, this book would not catch on fire. If on the other hand the book interacts with this heat source directly, it does ...
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Why can't the Earth's core melt the whole planet?

Earth core temperature is range between 4,400° Celsius (7,952° Fahrenheit) to about 6,000° Celsius (10,800° Fahrenheit). Source Why can't the Earth's core melt the whole planet? In other words, what ...
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Why does moving air feel colder? [duplicate]

If temperature is just the average kinetic energy of particles, why would moving air feel colder rather than warmer?
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Prove that negative absolute temperatures are actually hotter than positive absolute temperatures

Could someone provide me with a mathematical proof of why, a system with an absolute negative Kelvin temperature (such that of a spin system) is hotter than any system with a positive temperature (in ...
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Bush fires and heat waves, the real mechanics?

Like many others, I have been following the sad development of the bush/forest fires in Australia recently. A claim that gets repeated is that one of the contributors to this blaze is the ongoing >45°...
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What would happen if a 10-kg cube of iron, at a temperature close to 0 kelvin, suddenly appeared in your living room?

What would be the effect of placing an object that cold in an environment that warm? Would the room just get a little colder? Would it kill everyone in the room like some kind of cold bomb? What would ...
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Why do small patches of snow remain on the ground many days or weeks after all the other snow has melted?

I often notice small patches of snow that remain on the ground in seemingly random locations, many days or even weeks after all other snow in an area has melted, and even when temperatures have been ...
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How can interstellar space have a temperature of 2-3K?

Several different sources online state that the average temperature of interstellar space (or the universe in general) is around 2-3K. I learned that temperature is basically the wiggling of matter, ...
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Condensation of Water. Classroom Controversy

In our test there was a question that went like so: Question 4 You have a glass of iced water on an unshaded picnic table and went for a walk for 30 minutes. When you return you noticed the glass ...
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Why isn't temperature measured in Joules?

If we set the Boltzmann constant to $1$, then entropy would just be $\ln \Omega$, temperature would be measured in $\text{joules}$ ($\,\text{J}\,$), and average kinetic energy would be an integer ...
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Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth?

Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth? It's not just a subtle difference, but significant in my ...
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Does the halflife time of a radioactive material decrease if its temperature increases?

If at high temperatures atoms are more intensely interacting with each other or emitted photons that also could make the core vibrate. Is in these circumstances the radioactive material more likely to ...
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When snow falls, temperature rises. Is this due to entropy?

A friend of mine told me that temperature rises when snow falls. And this is because condensation of water in snowflakes reduces entropy and the temperature of the air rises to compensate for this. Is ...
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How does defrosting your freezer save energy?

I've been told I should defrost my freezer to save energy, wiki, here and here for example, but none of the linked sites is a peer-reviewed paper explaining why (the wiki article doesn't even have ...
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Sun's power density compared to a compost heap

According to Wikipedia the Sun's "power density" is "approximately 276.5 $W/m^3$, a value that more nearly approximates that of reptile metabolism or a compost pile than of a thermonuclear bomb." My ...
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What exactly is heat?

Is it energy? Is it energy per unit volume? Is it energy per unit time i.e power? What is it?
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When I put my hand on a hot solid why don't the particles transfering heat to my hand exert a force on it?

When I put my hand on a hot metal (say) solid, I can feel my hand heating up. I suspect this is caused mostly by particles (electrons, atoms, ...?) from the solid colliding with the particles that ...
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If temperature is amount of kinetic energy of particles, then how can there be a cold breeze? [duplicate]

When we put hands on A/C it gives cold winds. These winds have high kinetic energy but low temperature. How ? *don't confuse with A/C being heat pump , just an example, take antarctic blizzards. I can'...
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Why is high temperature superconductivity so hard to solve?

The phenomenon of high temperature superconductivity has been known for decades, particularly layered cuprate superconductors. We know the precise lattice structure of the materials. We know the band ...
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How loud is the thermal motion of air molecules?

In other words, given a magical room with walls that produce no vibration and transmit zero vibration from the outside, and nothing on the inside except room temperature air, what would be the noise ...
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Is it possible to "cook" pasta at room temperature with low enough pressure?

It is known fact, that boiling point of water decreases by decreasing of pressure. So there is a pressure at which water boils at room temperature. Would it be possible to cook e.g. pasta at room ...
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Why does the gas get cold when I spray it?

When you spray gas from a compressed spray, the gas gets very cold, even though, the compressed spray is in the room temperature. I think, when it goes from high pressure to lower one, it gets cold, ...
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Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?

This is a problem I just started puzzling over, and I felt this would be a good forum to check my reasoning. So here are the relevant observations followed by my question: Water achieves its maximum ...
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How can water evaporate at room temperature? [duplicate]

Boiling point of water is 100 degree Celsius. The temperature at which water in liquid form is converted into gaseous form. Then how it possible for water to evaporate at room temperature?
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Is it heat that causes vibrations on particles or is it the vibrations that causes the heat?

I was taught that molecules move more random when its hot. I am just wondering what really is it that causes something to heat up.
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How is it possible that it can get hotter in the car than it is outside?

The Law of Thermodynamics says that two bodies will eventually have equal temperatures. How is it possible that when you leave your car in the sun, it gets hotter in the car than it is outside? Why ...
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How can it be that the beginning universe had a high temperature and a low entropy at the same time?

The Big Bang theory assumes that our universe started from a very/infinitely dense and extremely/infinitely hot state. But on the other side, it is often claimed that our universe must have been ...
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Is helium liquid at 0 K?

I just saw in the dynamic periodic table that He is liquid at $-273.15\ ^\circ \rm C$. Is that true? How is that even possible? Can someone explain?

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