Ok, we have been pounding on the idea that heat is really just kinetic energy, and we are going to take it a little farther gain, hopefully in the pursuit of clarity.
As we know from the previous blog posts, the heat of a substance is the motions of its molecules. At some point of low temperature it’s obvious that there must be an end point, since if there is no movement of any of the molecules the effective energy is zero. That zero point is known as absolute zero and is equal to zero Kelvin. Typically in physics when referring to temperature the Kelvin scale is used. This is convenient since the standard equation for the energy of any system is based squarely on Kelvin.
E=2x10^-23T^k
E=Energy, T=Temperature in (k) Kelvin
No need remember this equation just the simplicity of its implications. Temperature is just the kinetic energy…when at the same temperature the energy of the molecules and atoms of the air are the same as those in a piece of paper, or a desk, or a pillow. The difficulty part is that these energies have to be measured per molecule and this fact eluded great minds for centuries, but the byproducts are intuitive. It is this very simplicity that some physicists like Richard Muller have pointed out is the “beauty” of physics. It’s not a traditional beauty; it’s the beauty of the simplicity, the beauty of the fact that when striped of its erudite mathematics the core principles are clear and reasonable.
To take ideas we discussed in the previous blog a step farther let’s apply what we have learned about increasing the energy or heat of a substance to solids. We considered that due to the low mass of atoms like helium, at room temperature in order to comply with the zeroth law of thermodynamics their velocity must be very high. When confined in a container like a bloom their high velocity causes them to collide with vigor and throw each other apart. The result is the average density of a helium balloon is less then that of the atmosphere allowing it to rise. If you place a helium balloon on a pool of liquid hydrogen (20.28K,-252.87Celcius) this will cause the helium atoms to cool and the result is quite clear as the balloon will contract and become smaller. Again this is because the velocity of the helium atoms has decreased as they cool and they then collide less frequently and with less energy.
The effect of the increase of temperature and kinetic energy is also relevant in solids. Typically solids expand by 1 part in 1000 to 1 part in 100,000 for every degree Kelvin (side note 1 degree Celsius = 1 degree Kelvin) increase. This may sound like a nominal amount but if one considers a structure like a suspension bridge the implications are necessary to consider. A bridge like the Verrazano-Narrows Bridge in Brooklyn which has a main span of over 4000 ft experience temperature swings of up to 30 degree Kelvin. The by product of this is an expansion or contraction of up to 2 feet. In addition the cables that transmit the weight of the bridge also contract or expand with temperature causing the center of the bridge to be 12 ft higher in the winger then the summer.
Another interesting byproduct of this is induced by the much hyped global warming. We have all heard over and over ad nauseum of the alarmingly imminent rise in sea-level due to global warming. The common misconception is that solely the glacial melting will increase the overall volume of the oceans thereby pushing up the sea level catastrophically. And although this could contribute nominally to a rise in global sea levels the sneaky culprit may really be the byproducts of heat expansion. The volume expansion of water is 2x10^-4 per degree Kelvin. Given this the math works out such that with an average ocean depth of 12,000 ft a rise in temperature of 5 degrees Kelvin (9 Fahrenheit) would equate to a rise in average sea level of approximately 6 feet. This rise caused by heat / kinetic energy induced expansion is enough to overwhelm most of the populated areas of Florida. (There are some details on quirky dynamics of water around 4 degrees Celsius that modify the more specific outcome of these equations, but the end result is still enough to account for flooding Florida’s populated areas and many other littoral populaces.)
Showing posts with label kinetic. Show all posts
Showing posts with label kinetic. Show all posts
Thursday, April 8, 2010
Friday, March 26, 2010
More on Heat and Energy: Where is all the Hydrogen?
More on Heat and Energy: Where is all the Hydrogen?
In an earlier blog we address the fact that Hydrogen is not a truly clean alternative fuel. This is because hydrogen is not an available resource on this planet. It has to be manufactured which is a dirty process in itself. So the question is where is all the Hydrogen?
This is a relevant question considering Hydrogen is the most abundant visible element in the universe. It makes up the majority of the mass of the sun and most stars. Jupiter is 89% hydrogen, Saturn is 96% hydrogen…so what’s with earth?
Well to answer this question we need to take a brief look at the Zeroth Law of Thermodynamics.
Interestingly the zeroth law of thermodynamic is one of the most important laws discovered in science. Unfortunately it was not fully understood until after the first three laws where numbered and detailed, and dubbing it the 4th law seemed inappropriate. So in the 1920s Ralph Fowler a British physicist coined the term zeroth law to mark its significance. Although it’s erudite aspects took fertile and deep minds to resolve, its application is very simple in everyday experience.
When two things touch each other they tend to reach the same temperature. The more surface area in contact the greater the transfer of energy. Place a hot cup of coffee on a cold desk and it will get cold quick, place it with a small edge on the desk and the other on edge on a raised surface such as a post-it stack, and the surface of the bottom of the cup will be mostly in contact with cold air rather then the cold desk. Since air is not near the conductor of energy as average desk the coffee stay warmer longer. A simple thermometer works on the same principle. When a thermometer is in the air it tends to reach the same temperature as the air. This is true because the molecules in the air impart their kinetic energy too the molecules in the thermometer if the air is warmer. In the event the air is colder the molecules in the thermometer are more energetic then the molecules in the air and as the energetic molecules on the thermometer surface strike air molecules they lose energy to the air, much like a q-ball will stop or slow when it strikes a stationary ball on a pool table. This happens millions or billions of times and eventually the thermometer will either lose or give the kinetic energy of the motion of its molecules to the air if it was initially warmer then the air, or if the thermometer is initially colder it will acquire energy from the air. Either way, the air and thermometer will come to the same relative energy or temperature. Only when the relative energies or temperature of the two objects are the same does the flow of energies cease.
Now with that in mind, one more small detail is necessary to clarify. Just because two objects have the same temperature does not mean necessarily that the molecules in the objects are moving at the same speed. Since the temperature is the kinetic energy of the molecules this would make one thing clear, the smaller the molecule the faster it would have to move to have energy. Since energy is a product of the velocity and the mass, a molecule that is larger would move slower then a small molecule and yet have the same energy. This is much like a pool ball would have to be traveling at a considerably higher speed then a bowling ball to scatter the pins at the end of a bowling lane with the same vigor. In a similar fashion if one imagined a baseball moving at 90mph one can accept that a professional catcher could manage to catch it, but if one visualized a bowling ball traveling at 90mph striking a catcher we can reason the results would be dire. This is because the energy of the item is a product of speed and mass. So since this is true, in materials made up larger molecules their molecules average velocity would be less then materials at the same temperature made up of smaller molecules.
Ok, so once one can absorb the information above one can see why there is no or little hydrogen in earth’s atmosphere. If hydrogen was released into the atmosphere, because of the zeroth law of thermodynamics, we could reasonably conclude that it would have to reach the same temperature, and same energy as the air around it. That said, its velocity would have to be substantial enough to allow it to have the same kinetic energy as the surrounding air. Now with that in mind consider that hydrogen is the lightest of all atoms…it’s miserably lacking in mass, in fact its 1/16 the weight of oxygen. So in order to come to the same energy it has to move incredibly fast, so fast it actually has a velocity significant enough to escape the pull of earth’s gravity. Over time due to the average velocity that allows hydrogen atoms to exceed earths escape velocity ( we will go over escape velocity in later blogs) of approximately 25,000 mph frequently enough that eventually the majority of hydrogen has escaped our atmosphere. So because of zeroth law, kinetic energy, and high velocities hydrogen is scarce.
Few things to ponder now that we have clarified these points…what makes a helium balloon or hot air balloon rise? Most think it’s because helium or hot air is “lighter” or more “buoyant”…but the real reason is in the details above and revolve around energy, and velocity.
What makes your voice sound funny when you breathe helium? Some believe it’s because it affects your vocal cords, or that the pitch changes. When in reality helium has little or no effect on your vocal cords, and in fact the pitch of ones voice does not change. Rather, it’s the timber of your voice that changes, and the details of why are again found in the facts above.
In an earlier blog we address the fact that Hydrogen is not a truly clean alternative fuel. This is because hydrogen is not an available resource on this planet. It has to be manufactured which is a dirty process in itself. So the question is where is all the Hydrogen?
This is a relevant question considering Hydrogen is the most abundant visible element in the universe. It makes up the majority of the mass of the sun and most stars. Jupiter is 89% hydrogen, Saturn is 96% hydrogen…so what’s with earth?
Well to answer this question we need to take a brief look at the Zeroth Law of Thermodynamics.
Interestingly the zeroth law of thermodynamic is one of the most important laws discovered in science. Unfortunately it was not fully understood until after the first three laws where numbered and detailed, and dubbing it the 4th law seemed inappropriate. So in the 1920s Ralph Fowler a British physicist coined the term zeroth law to mark its significance. Although it’s erudite aspects took fertile and deep minds to resolve, its application is very simple in everyday experience.
When two things touch each other they tend to reach the same temperature. The more surface area in contact the greater the transfer of energy. Place a hot cup of coffee on a cold desk and it will get cold quick, place it with a small edge on the desk and the other on edge on a raised surface such as a post-it stack, and the surface of the bottom of the cup will be mostly in contact with cold air rather then the cold desk. Since air is not near the conductor of energy as average desk the coffee stay warmer longer. A simple thermometer works on the same principle. When a thermometer is in the air it tends to reach the same temperature as the air. This is true because the molecules in the air impart their kinetic energy too the molecules in the thermometer if the air is warmer. In the event the air is colder the molecules in the thermometer are more energetic then the molecules in the air and as the energetic molecules on the thermometer surface strike air molecules they lose energy to the air, much like a q-ball will stop or slow when it strikes a stationary ball on a pool table. This happens millions or billions of times and eventually the thermometer will either lose or give the kinetic energy of the motion of its molecules to the air if it was initially warmer then the air, or if the thermometer is initially colder it will acquire energy from the air. Either way, the air and thermometer will come to the same relative energy or temperature. Only when the relative energies or temperature of the two objects are the same does the flow of energies cease.
Now with that in mind, one more small detail is necessary to clarify. Just because two objects have the same temperature does not mean necessarily that the molecules in the objects are moving at the same speed. Since the temperature is the kinetic energy of the molecules this would make one thing clear, the smaller the molecule the faster it would have to move to have energy. Since energy is a product of the velocity and the mass, a molecule that is larger would move slower then a small molecule and yet have the same energy. This is much like a pool ball would have to be traveling at a considerably higher speed then a bowling ball to scatter the pins at the end of a bowling lane with the same vigor. In a similar fashion if one imagined a baseball moving at 90mph one can accept that a professional catcher could manage to catch it, but if one visualized a bowling ball traveling at 90mph striking a catcher we can reason the results would be dire. This is because the energy of the item is a product of speed and mass. So since this is true, in materials made up larger molecules their molecules average velocity would be less then materials at the same temperature made up of smaller molecules.
Ok, so once one can absorb the information above one can see why there is no or little hydrogen in earth’s atmosphere. If hydrogen was released into the atmosphere, because of the zeroth law of thermodynamics, we could reasonably conclude that it would have to reach the same temperature, and same energy as the air around it. That said, its velocity would have to be substantial enough to allow it to have the same kinetic energy as the surrounding air. Now with that in mind consider that hydrogen is the lightest of all atoms…it’s miserably lacking in mass, in fact its 1/16 the weight of oxygen. So in order to come to the same energy it has to move incredibly fast, so fast it actually has a velocity significant enough to escape the pull of earth’s gravity. Over time due to the average velocity that allows hydrogen atoms to exceed earths escape velocity ( we will go over escape velocity in later blogs) of approximately 25,000 mph frequently enough that eventually the majority of hydrogen has escaped our atmosphere. So because of zeroth law, kinetic energy, and high velocities hydrogen is scarce.
Few things to ponder now that we have clarified these points…what makes a helium balloon or hot air balloon rise? Most think it’s because helium or hot air is “lighter” or more “buoyant”…but the real reason is in the details above and revolve around energy, and velocity.
What makes your voice sound funny when you breathe helium? Some believe it’s because it affects your vocal cords, or that the pitch changes. When in reality helium has little or no effect on your vocal cords, and in fact the pitch of ones voice does not change. Rather, it’s the timber of your voice that changes, and the details of why are again found in the facts above.
Thursday, March 11, 2010
What is Heat?
What is Heat? Interestingly to build on last week’s blog, heat is kinetic energy. But we will address in particular a bit later. First let’s think about what everything is made of.
All substances are made up of atoms, of which only about 92 are of available in nature. From there, atoms combine to form molecules. Molecules are chains or collections of atoms. These chains or collections come in various structures and shapes and this determines to a great degree the way we perceive, interact, or can manipulate them at a macroscopic – real world – level.
A good example of this is water. Often we see expressions of the atomic structure of molecules, such as water which is expressed as H2O. This signifies that the molecule water consists of 2 atoms of Hydrogen and one atom of Oxygen. A water molecule is dipolar, which means that there is an opposite charge on each end of the atom. The Hydrogen’s come together at one end and the Oxygen at the other. Since the Oxygen atom has a slightly higher electronegativty, it causes this end of the water molecule to have a slightly negative charge, and the Hydrogen end to a manifest a positive charge. This charge can be seen if one takes a comb that has a slight negative charge on it from running it through hair, and holds it near a narrow stream of falling water. The electronegative electrons left behind on the comb will attract the slight positive charge of the hydrogen atoms in water and cause it to bend or be attracted toward the charged comb.
Another example that is unique to water and dictated by its atomic structure is its being known as the “universal solvent.” This means that water has the amazing ability to break down many other substances and act as a solvent. Again this is a by product of its dipolar structure. As an example, typical table salt or NaCl which consist of the separately toxic substances of Sodium and Chlorine is easily dissolved in water. After juggling an electron, the electropositive charge of the sodium binds well with the electronegative charge of the chlorine atoms, creating a stable ionic bond in the absence of water. When water is introduced the dipolar nature of water is insidious. The positive charge of the two hydrogen atoms pulls the negative charge of the salts chlorine and the negative charge of the waters oxygen attracts the sodium. And through a divide and conquer method repeated billions of times the divisive charges of the water atoms overwhelms the ionic bond of the NaCl breaks it down. Most any substance whose electromagnetic bonds can not overcome the small but abundant dipolar H2O atoms are soluble in water.
Ok, so now that we have addressed a couple examples of how atoms although extraordinarily small can have and macroscopic effect we can address heat briefly.
What is heat?
In ordinary substances the molecules that constitute a substances structure are constantly in motion. They continually bounce off each other and off other and other materials they come into contact with. This motion is universal and constant, and the hotter a material gets the faster on average these molecules and atoms move and bounce off each other. Conversely the colder something is the slower or less vigorously the molecules move, that is until one reaches zero Kelvin where theoretically the motion of all the molecules ceases. So how can we observe this in real life? Well, when one rubs their hands together, the friction speeds up slightly the molecules in the hand, and they intern propagate their motion by bouncing off adjacent molecules and ultimately the average speed of the molecules in your hand increases, and thereby the heat or warmth increases. And how fast on average to molecules move in a substance? Well interestingly it works out at room temperature to be about the speed of sound. And remember that although a molecule is moving fast, it can not move far without bumping into another molecule and bouncing off. Because of this each individual molecule does not move far over time but rather experience a slow random walk.
So again, what is heat, well heat is kinetic energy. Heat is the individual motion of a molecule running into another molecule, imparting its kinetic or motion energy on the adjacent molecule. So when a pot of water is heated up, the molecules average speed increased. Each individual molecule on average gains a little more speed, and from this a little bit more kinetic energy. Then if one takes their hand which is approximately 99 degrees and in which the individual molecules are moving slower on average then in the boiling water, and places it in the water, the individual molecules of the water collide with the skin molecules and impart their acceleration and energy to your hand. This energy or acceleration of the molecules in ones hand is perceived as heat, or in the case of boiling water, enough energy or speed is imparted to result in damaging the skin cells. So heat is kinetic energy.
All substances are made up of atoms, of which only about 92 are of available in nature. From there, atoms combine to form molecules. Molecules are chains or collections of atoms. These chains or collections come in various structures and shapes and this determines to a great degree the way we perceive, interact, or can manipulate them at a macroscopic – real world – level.
A good example of this is water. Often we see expressions of the atomic structure of molecules, such as water which is expressed as H2O. This signifies that the molecule water consists of 2 atoms of Hydrogen and one atom of Oxygen. A water molecule is dipolar, which means that there is an opposite charge on each end of the atom. The Hydrogen’s come together at one end and the Oxygen at the other. Since the Oxygen atom has a slightly higher electronegativty, it causes this end of the water molecule to have a slightly negative charge, and the Hydrogen end to a manifest a positive charge. This charge can be seen if one takes a comb that has a slight negative charge on it from running it through hair, and holds it near a narrow stream of falling water. The electronegative electrons left behind on the comb will attract the slight positive charge of the hydrogen atoms in water and cause it to bend or be attracted toward the charged comb.
Another example that is unique to water and dictated by its atomic structure is its being known as the “universal solvent.” This means that water has the amazing ability to break down many other substances and act as a solvent. Again this is a by product of its dipolar structure. As an example, typical table salt or NaCl which consist of the separately toxic substances of Sodium and Chlorine is easily dissolved in water. After juggling an electron, the electropositive charge of the sodium binds well with the electronegative charge of the chlorine atoms, creating a stable ionic bond in the absence of water. When water is introduced the dipolar nature of water is insidious. The positive charge of the two hydrogen atoms pulls the negative charge of the salts chlorine and the negative charge of the waters oxygen attracts the sodium. And through a divide and conquer method repeated billions of times the divisive charges of the water atoms overwhelms the ionic bond of the NaCl breaks it down. Most any substance whose electromagnetic bonds can not overcome the small but abundant dipolar H2O atoms are soluble in water.
Ok, so now that we have addressed a couple examples of how atoms although extraordinarily small can have and macroscopic effect we can address heat briefly.
What is heat?
In ordinary substances the molecules that constitute a substances structure are constantly in motion. They continually bounce off each other and off other and other materials they come into contact with. This motion is universal and constant, and the hotter a material gets the faster on average these molecules and atoms move and bounce off each other. Conversely the colder something is the slower or less vigorously the molecules move, that is until one reaches zero Kelvin where theoretically the motion of all the molecules ceases. So how can we observe this in real life? Well, when one rubs their hands together, the friction speeds up slightly the molecules in the hand, and they intern propagate their motion by bouncing off adjacent molecules and ultimately the average speed of the molecules in your hand increases, and thereby the heat or warmth increases. And how fast on average to molecules move in a substance? Well interestingly it works out at room temperature to be about the speed of sound. And remember that although a molecule is moving fast, it can not move far without bumping into another molecule and bouncing off. Because of this each individual molecule does not move far over time but rather experience a slow random walk.
So again, what is heat, well heat is kinetic energy. Heat is the individual motion of a molecule running into another molecule, imparting its kinetic or motion energy on the adjacent molecule. So when a pot of water is heated up, the molecules average speed increased. Each individual molecule on average gains a little more speed, and from this a little bit more kinetic energy. Then if one takes their hand which is approximately 99 degrees and in which the individual molecules are moving slower on average then in the boiling water, and places it in the water, the individual molecules of the water collide with the skin molecules and impart their acceleration and energy to your hand. This energy or acceleration of the molecules in ones hand is perceived as heat, or in the case of boiling water, enough energy or speed is imparted to result in damaging the skin cells. So heat is kinetic energy.
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