[1] Thermal Energy And "heat" First part of my thread series

[Baniboy 3]

First part of my thread series, enjoy. Oh and if I explained something incorrectly, feel free to correct me. Heat is the amount of thermal energy getting transfered(didn't expect that, hu? ). "So what is thermal energy, then, smart***?" - you may ask Thermal energy is the amount internal kinetic energy(And kinetic energy is motion/movement/whatever... ). Internal kinetic energy is the kinetic energy of the molecules and atoms random movement. Now we know that thermal energy is motion. So how does this energy transfer? There are three ways we know: ConductionThis is when the particles are in physical contact. When a particle collides with another one, it transfers part of its own kinetic energy to the other particle. This kind of transfer can only happen in physical contact. You can try this by rubbing your hands together for a few seconds, same thing happens. It doesn't matter if the object is solid, liquid or gas.RadiationThis is another transitional form of thermal energy. The radiation is created by electrons moving to upper energy levels and coming back closer to protons losing energy resulting in waves(radiation). Radiation can travel easily through space, even through a vacuum. It's called infrared radiation BTW, it travels at the speed of light. Nuclear reactions can cause radiation too, but it'll be much higher. You can calculate how much energy(not only thermal energy) nuclear reactions create by this: mass * speed of light?. I'll talk about this more on my next topic about fusion, fission and fire. Anyway, when something stops radiation(like a brick wall), it heats up(correctly: gains more thermal energy.) The object can also reflect energy. Living things are viewable in infrared cameras because they generate infrared radiation by chemical reactions in mitocondria (it's the part of the cell that burns material).ConvectionThis one isn't very important. To have thermal energy to transfer by convection, the matter has to be in liquid or gas form as flow is required for this. Simply, the object has thermal energy, it's moves to another location and mixes with other "stuff" with higher or lower amount of thermal energy. After the objects mix and become one(now conduction starts working), they have an average amount of thermal energy somewhere between the original ones. One example of this is air conditioning.There are upper and lower limits for thermal energy.Upper limitIt's the speed of light. The particles can't move faster than the speed of light, they can't even reach the speed of light. It's the upper limit for any form of energy if it relates with speed and mass.Lower limitThis is absolute zero. It's 0 Kelvin(Kelvin is the standard scientific unit to measure temperature and/or thermal energy). There can be no less internal kinetic energy than no internal kinetic energy. BUT, absolute zero can't be achieved because a) there will always be something giving the object more internal kinetic energy even if it's a closed system. the laws of quantum mechanics(too hard to explain right now what it means... google is your friend). By the laws of quantum mechanics I mean that if particle doesn't have any kinetic energy, it doesn't exist.Solid, liquid and gasThese are the forms of matter, and they depend on the amount of thermal energy. If you compress a lot of gas, you get a lot of heat. As gas needs heat to remain as gas, if you compress it, it'll turn into liquid. So all the internal kinetic energy has to go somewhere right? The same thing happens in your fridge, liquid is turned into gas, and gas absorbs the "heat", cooling your beer :DThe unit we measure heat with is called a calorie. 1 calorie is the amount of heat that needs to be transfered to 100 grams of water to raise it's temperature by 1 celsius or Kelvin. Thermal energy itself is measured by Joule (J) like any other form of energy.Thermal energy also means the potential energy of the object. The internal kinetic energy plus the potential energy form thermal energy. I mentioned this later so I wouldn't confuse you, but confuse you at the end :DI hope I haven't confused you much. So now you know, happy now?

Edited July 17, 2009 by Baniboy (see edit history)

[Polipop 0]

Interesting... And very educative. You know I'm not good at these things, so it's great to have the chance to read somo of this, To increase the poor knowledge of physics that I have. Though I don't know much about this, I'm always interested so I gotta say thanks for the time you took on writting this. I'll be longing to see more of your posts.

[Baniboy 3]

Interesting... And very educative. You know I'm not good at these things, so it's great to have the chance to read somo of this, To increase the poor knowledge of physics that I have. Though I don't know much about this, I'm always interested so I gotta say thanks for the time you took on writing this. I'll be longing to see more of your posts.

Thank you for reading and replying.

[rob86 2]

It's an interesting read. You should have typed Mass * speed of light^2 with it's commonly known formula - Einstein's theory of general relativity E=m.c^2 and not so scientific people would recognize it better an go "ooh! aah!" .. unless you were saving it for the next chapter as a surprise and I just ruined it? :)You should add a little bit to this thread about uh.. heat transfer I think it's called. It's useful information..tells you how long it takes to cool a drink?I believe the formula is q = /\T * S (I forget what they commonly use as a letter for Specific Heat?)That formula in english means Heat = Delta(Temperature) multiplied by Specific HeatHeat -- as Bani taught us -- is also energy, which is normally measured in Joules. Sound familiar ? -- it's used with electricity and means "watt second". It was named after the English physicist James Joule.Delta(T) means Change in temperature.. simply.. 15C to 30C is 15.. 15 to -15 is -30Specific Heat is the heat (energy!) required to raise the temperature of a substance one degree in Celsius (and Kelvin too if I remember correctly??). This number can be found on table of elements which are available everywhere online.Using this simple formula..you can do some cool calculations.. ofcourse there is more to it..like the energy to melt and freeze something (ice cubes)..but i forget that right now :DIf I'm wrong about something..feel free to correct me as it's been years since I've used this knowledge..Keep up the physics posts Bani..they are cool.

[Baniboy 3]

Actually "heat" in its scientific meaning is not energy, heat is the amount of thermal energy being transfered as I said in the post.

Watt is the unit to measure power. Power is simply means how fast something does a certain amount of work per certain amount of time(energy conversion). P(power) = w(work) / (time).

Electric power is: P = U * I. To put it simply: You get watts by multiplying the voltage and amperes with each other

 

I believe the formula is q = /\T * S (I forget what they commonly use as a letter for Specific Heat?)

If you mean thermal energy, it is marked with a capital E like any other energy form. If you're using multiple energy forms, you can make it simple by adding a small t(thermo/thermal energy/whatever that starts with t). Like this: E_t . Heat itself is measured by calories. I don't know about your "specific heat" tho...

 

 

You should have typed Mass * speed of light^2 with it's commonly known formula - Einstein's theory of general relativity E=m.c^2 and not so scientific people would recognize it better an go "ooh! aah!" .. unless you were saving it for the next chapter as a surprise and I just ruined it? smile.gif

No you didn't ruin anything, but I would've had to explain what the units mean so I left out the short version. Sorry to leave you without an "ooh aah".

[rob86 2]

You're right in saying that "Heat" is the amount of energy being transferred but it seems to be quite common to call "Heat" energy by itself even if it's inaccurate.

 

Q in that formula I believe stands for "Quantity of Heat being transferred" but obviously E or anything could be substituted

 

I actually made a mistake in the formula it is Q = m/\T * S with m being the mass of the object also written as q = m(Tf-To) * S in the second formula it's the same thing but you fill in final temperature subtract original temperature.

 

 

Here's an example question and answer.

 

You have a cup of water (250ml) at room temperature (20C) that you want to warm up to 68C for a cup of tea. How much "Heat" needs to be applied in Kilo Joules to raise the temperature?

 

q = m(Tf-To) * S

 

q = ?

m = .250kg (1ml h20 = 1g h20)

/\T = (Tf - To) = (68-20)

S = Specific Heat Capacity of H20 = 4.18kJ/kg * ?C.

 

q = .250g (68C-20C) * 4.18KJ/kg * C

q = 12000g.c * 4.18KJ/kg * C

q = 50.16KJ

 

50.2 KJ of Heat need be applied to raise the temperature.

 

I think that's right........ it's been a while and it's harder to understand typed out..

 

It might have a more complicated name than "heat transfer formula" because I can't seem to find it anywhere!

[Baniboy 3]

That just tells how much heat you need, not how fast you heat it up. (correct if I'm mistaken)This is how I would do it:1 calorie = amount of heat required to raise the temperature of 1 gram of water by 1 Kelvin1 calorie = 4,18400 JoulesMass = about 250 grams4,18400 J * 250 g * 48 = 50208 JAs a reminder, I suggest that you always calculate with the units in their "standard form". It's possible to mess them up if you convert Joules into kilojoules and seconds to hours. When you're working with time, you have to always convert stuff back, because time doesn't work the way our other units of measurements work.Now if you have a heating device that has "100 watts"-sticker, you can calculate how much time it takes you to heat up that amount of water.We know how the power of the device, and we know how many Joules we need to be converted into thermal energy (or heat in normal language ). We should get the amount of seconds like this:P = w/tWe know that (using the standard form of units) 100 watts = 100 J / 1 sSo how long it takes for our device to heat that up? We calculate how many times 100 can fit into 50208:50208 J / 100 = 502,08 s After some conversion to minutes the result is around 8 minutes and 22 seconds

[iGuest 3]

question[1] Thermal Energy And "heat"

how does radiation occur in a cup of tea?

don't have email but think your ad is great. Would it be possible for you to add the answer to the website?

hope so. Thanks for all the advice...

-question by jessica graham

[Baniboy 3]

question

[1] Thermal Energy And "heat"

 

how does radiation occur in a cup of tea?

 

don't have email but think your ad is great. Would it be possible for you to add the answer to the website?

 

hope so. Thanks for all the advice...

 

-question by jessica graham

Which website? This forum or somewhere else? Sorry for the late reply.

Well this doesn't exactly have anything to do with thermal energy, but I'll answer.

If that cup of tea has something that contains unstable atoms then it is possible. This is called radioactive decay. This is when an unstable isotope slowly(or rapidly) get ripped apart. Examples of these can be Iodine and Cesium.

 

Find out more on these topics:

 

http://forums.xisto.com/topic/68143-2-fusion-this-one-came-out-a-little-late-but-oh-well/

http://forums.xisto.com/topic/68167-3-nuclear-fission-read-it/

[getube 0]

Temperature is a measure of the level of random movement of particles. When we touch an icecube we feel cold becouse the level of random movement is high in our hand than in icecube.Heat is total amound of energy of all particles which are in random motion.(it not include potentail, nuclear,... energy of particles)Am I right?

Edited December 22, 2009 by getube (see edit history)

[Baniboy 3]

Temperature is a measure of the level of random movement of particles. When we touch an icecube we feel cold becouse the level of random movement is high in our hand than in icecube.Heat is total amound of energy of all particles which are in random motion.(it not include potentail, nuclear,... energy of particles)

Am I right?

Practically, yes. But you used the wrong words.
Heat is the thermal energy in transfer. Temperature is used to measure how rapidly it transfers. By heat I assume you mean thermal energy, as it is usually referred to as heat.

When you touch the ice cube, rapidly moving particles collide with the ice cube's particles in the surface. The particles in your hand slow down because they just transfered some of their kinetic energy to the ice cube. And you feel cold.

[onkarnath2001 0]

First part of my thread series, enjoy. Oh and if I explained something incorrectly, feel free to correct me.
Heat is the amount of thermal energy getting transfered(didn't expect that, hu? ). "So what is thermal energy, then, smart***?" - you may ask
Thermal energy is the amount internal kinetic energy(And kinetic energy is motion/movement/whatever... ). Internal kinetic energy is the kinetic energy of the molecules and atoms random movement.

Now we know that thermal energy is motion. So how does this energy transfer?

There are three ways we know:

Conduction
This is when the particles are in physical contact. When a particle collides with another one, it transfers part of its own kinetic energy to the other particle. This kind of transfer can only happen in physical contact. You can try this by rubbing your hands together for a few seconds, same thing happens. It doesn't matter if the object is solid, liquid or gas.

Radiation
This is another transitional form of thermal energy. The radiation is created by electrons moving to upper energy levels and coming back closer to protons losing energy resulting in waves(radiation). Radiation can travel easily through space, even through a vacuum. It's called infrared radiation BTW, it travels at the speed of light. Nuclear reactions can cause radiation too, but it'll be much higher. You can calculate how much energy(not only thermal energy) nuclear reactions create by this: mass * speed of light˛. I'll talk about this more on my next topic about fusion, fission and fire. Anyway, when something stops radiation(like a brick wall), it heats up(correctly: gains more thermal energy.) The object can also reflect energy. Living things are viewable in infrared cameras because they generate infrared radiation by chemical reactions in mitocondria (it's the part of the cell that burns material).

Convection
This one isn't very important. To have thermal energy to transfer by convection, the matter has to be in liquid or gas form as flow is required for this. Simply, the object has thermal energy, it's moves to another location and mixes with other "stuff" with higher or lower amount of thermal energy. After the objects mix and become one(now conduction starts working), they have an average amount of thermal energy somewhere between the original ones. One example of this is air conditioning.

There are upper and lower limits for thermal energy.

Upper limit
It's the speed of light. The particles can't move faster than the speed of light, they can't even reach the speed of light. It's the upper limit for any form of energy if it relates with speed and mass.

Lower limit
This is absolute zero. It's 0 Kelvin(Kelvin is the standard scientific unit to measure temperature and/or thermal energy). There can be no less internal kinetic energy than no internal kinetic energy. BUT, absolute zero can't be achieved because a) there will always be something giving the object more internal kinetic energy even if it's a closed system. the laws of quantum mechanics(too hard to explain right now what it means... google is your friend). By the laws of quantum mechanics I mean that if particle doesn't have any kinetic energy, it doesn't exist.

Solid, liquid and gas
These are the forms of matter, and they depend on the amount of thermal energy. If you compress a lot of gas, you get a lot of heat. As gas needs heat to remain as gas, if you compress it, it'll turn into liquid. So all the internal kinetic energy has to go somewhere right? The same thing happens in your fridge, liquid is turned into gas, and gas absorbs the "heat", cooling your beer

The unit we measure heat with is called a calorie. 1 calorie is the amount of heat that needs to be transfered to 100 grams of water to raise it's temperature by 1 celsius or Kelvin. Thermal energy itself is measured by Joule (J) like any other form of energy.

Thermal energy also means the potential energy of the object. The internal kinetic energy plus the potential energy form thermal energy. I mentioned this later so I wouldn't confuse you, but confuse you at the end

I hope I haven't confused you much. So now you know, happy now?

not confusing sir,,interesting and knowledge gaining but i want to know that if heat produces thermal energy and the world is just becoming crazy for energy sources like we are consuming a lot of petrol or diesel or cooking gas and there is a deficiency of alternative energy source.then why not the scientists are moving their legs towards thermal energy while we have a great and enormous resource of heat or thermal energy what we know as the sun?????????????
can it not be a source of continuous and endless energy????????????

[Baniboy 3]

Yes. I think there is a power plant in Arizona that works by directing sun's energy into water to heat it up using mirrors. And there also can be sun panels which use the light to produce electricity.But in many areas of the globe, for example in Finland where I live, there isn't sunlight all year long. This would make the country's power source dependent on other countries. To make such thing work, we would need perfect world peace. There wouldn't any fear of anyone cutting the power off.Another thing would be injustice! Does someone living near the equator deserve the wealth that their resource gives them more than someone who lives near the poles? No? Yes? So all countries would have to abandon their borders, share all the power, and the ones that use more power than other would have to pay more for the maintenance as well.Many summer cottages are using sun panels here already as their power source, as you have sunlight almost 24/7 here at summer.Another problem is something impossible to solve. We have exceeded the carrying capacity of our planet. We consume more energy than the global ecosystem would require us to stay stable. In other words: we're all gonna die.