12 replies to this topic

[Baniboy]

getube, on Dec 22 2009, 05:55 AM, said:

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]

Baniboy, on Jul 18 2009, 01:04 AM, said:

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 light². 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]

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.