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The Science of 'Heat'
What actually is Heat?
- 'Energy transferred from one body to another due to a difference in temperature'. is one statement shown on the Internet.
It does really tell you what heat actually is. Technically the statement isn't actually true. Temperature is a comparative measurement made up by humans. It doesn't actually exist. Humans for thousands of years didn't have 'temperature'. Eventually scientists decided to compare the three states of H2O to other substances. To enable a comparison between when ice became water and water became a gas scientists invented a thin glass tube that contained a substance that expanded with a change in 'temperature' of a substance. To quantify the change increments were marked on the tube. Fahrenheit made 32 increments based on a mathematical calculation. Later Celsius divided his tube into 100 increments which gave a more precise measurement.
Heat is not the amount of energy transferred from one body to another due to a difference in temperature. Latent heat transfers a massive amount of energy without any change in temperature. Heat is a product of collisions.
Heat is actually a product of impacts between electrons. Electrons are negatively charged and orbit around a Nucleus of Protons and in most cases Neutrons. The nucleus is positively charged and like all magnets a negative attracts a positive. Before someone says it is the other way round it will all be explained in another blog.
For the electrons to whiz around the nucleus energy is required. No energy and the electrons cannot move. At that point they cannot collide with any other electrons, therefore cannot produce 'Heat'. It is termed 'Absolute Zero' with a comparative temperature of minus 273.15°C. The unit of Kelvins is used, hence zero Kelvins (0K). Note it is not degrees Kelvin - just Kelvin.
The theory that when there is no electron movement there can be no thermal production dates back to the late 1800s. There were several scientists pondering over similar theories on the Continent and in Scandinavia. They had discovered that as the electrons around the nucleus slowed down the thermal output reduced. i.e the temperature dropped.
William Thomson was a professor at the University of Glasgow. Although his subject was Natural Philosophy, he was also very interested in electricity, mathematics and physics. Reading the works of others, Thomson formulated his theory that when electrons stop moving there can be no thermal production. For his work in the field of physics he was honoured to become 1st Baron Kelvin. (Named after the River Kelvin that flows in Glasgow).
Heat is the measure of thermal energy in matter. Francis Bacon about 400 years ago is reported to have started the theory that ‘heat was a brisk agitation of the particles of matter’, the birth of the theory of kinetic energy. But what is kinetic energy?
Rub the palms of your hands together and additional heat will be produced, why? It is friction where the molecules that make up the skin are rubbing against another surface of skin causing the surface molecule to collide. Clap your hand together for the same amount of time will not produce the same increase in temperature though. Although the molecules are still colliding, the small amount of heat produced is being lost to the air as it is being forced from between the hands – heat loss.
A few years later in 1906 Walter Nernst formulated another theory that absolute zero must be unattainable which became the ‘Third Law of Thermodynamics’.
So what is 'thermal energy?'
Simply put, it is the energy used to mobilise atoms, more specifically the electrons. Energy mainly originates as radiation from the Sun and Radio Active minerals in the Earth's core such as Uranium. Radiation has no substance. It is thought to be both electric and magnetic. Given the term 'electromagnetic' radiation it leaves the burning Sun in minute spurts, or packages known as 'photons'.
Electricity has no substance. The result of the movement can be seen, but not the actual electricity. Likewise, magnetism also has no substance. It cannot be seen, only the result of its existence.
Electromagnetism leaving the Sun travels at a very high speed. 299,792,458 metres per second. That is about 186,000 miles per second.
Radiation from the Sun has been debated over many centuries. Famous scientists / physicists have said it travels as waves, whilst others have stated it cannot as there is no substance. The truth is science cannot really explain energy.
The current theory is electromagnetic energy travels in Sine waves transversely. That means the electric wave travels as a Sine wave at right angles to the magnetic wave. That is the stumbling block with science as stated by Einstein. A wave can only exist if there is a substance. Waves on water cannot exist if there is no water. He further added that if there were matter / a substance that enabled the radiation to travel as waves, the amount of energy required would be beyond possibility.
An example: The Sun is about 93,000,000 miles away. It takes about 8.3 minutes for a photon to arrive over that distance. There are Stars millions of light years away. Their radiation is still whizzing past the Earth. In theory, unless the radiation collides with matter, be it a solitary atom or a mass as big as Jupiter, it will keep on going. That is an awful lot of energy required. Hence it is safe to say even the scientists cannot actually agree on what energy actually is.
Based on what we are led to believe, energy is electromagnetic movement, and our current understanding about electricity and magnetism the following can be assumed.
Can you feel the heat from the Sun?
Quite simply - No. It is too far away and radiation has no temperature as there is no substance.
Why do I feel hot when I Sun bathe?
Radiation is like billions of minute bar magnets. Imagine the magnets rotating so the negative and positive ends are constantly moving. The cells that make up your body are made up from billions of atoms. Each atom has electrons whizzing around their nucleus. The electrons are negatively charged. That means the radiation is hitting positively and then negatively making your skin cells energised.
Your skin cells cannot go whizzing off (hopefully not), so at best can only vibrate and collide with adjacent cells. That is where the 'heat' is being generated from. The radiation is just the energy required.
More proof required?
Leave a book open with the white pages fully exposed to Sunlight all day on a hot day. Place something solid like a stone or coin on the page and leave it. Next day, remove the stone or coin and you will likely see a difference in colour of the paper. Just like your skin in strong Sunlight will burn / tan, so the paper will burn change colour. Print may actually fade as it very slowly combusts. But there was no heat whatsoever in the radiation.
Okay - How is it the air is warmer?
Air has molecules and atoms. Radiation is so small that it collides with the atoms and bounces them about. The radiation also bounces off the atoms and goes in other directions. The radiation that has not collided with atoms in the air arrives at the surface energises everything it hits.
You may have seen people who can fry an egg on the bonnet of their car demonstrating how hot the hood is. The heat has been produced by all the atoms in the paint and metal becoming super activated. They really collide with all their adjacent atoms and produce a lot of heat.
That heat is given off as radiation again and some by conduction with the atoms and molecules in the air. As they become energised they can move much faster as they are in a gas format. The air as it is energised expands and convection currents take the highly energised air atoms and molecules upwards and are replaced by the cooler, slower atoms and molecules = the air becomes warmer.
How can slowing down atoms and molecules be proven?
An example is H2O. Atoms of Oxygen and Hydrogen bond together to produce a molecule.
The molecules are 'polar'. That means they have a 'Positive side' and a 'negative side' just like a bar magnet.
Depending upon how much energy they are given will dictate how fast and far they can travel. Lots of energy and they will move much faster, collide more and won't want to hang around with other H2O molecules. They are in the invisible gaseous state.
When their energy levels fall, they slow down. Less collisions so less heat is produced. As they slow down the magnetic force starts to have an effect again. The molecules become closer together, still very mobile, but also become visible. That is what steam, mist and fog are. The molecules are closer together and therefore condensing / reducing in volume.
Slow the molecules even more and they bond with each other to become water, a liquid. H2O molecules are particular with what they want to bond with. Nitrogen atoms make up most of the air with Oxygen. H2O molecules prefer each other far more than the other atoms so they pull tightly together to form a skin like surface. Termed 'surface tension' H2O molecules will pack themselves into the smallest volume possible. That is why water tends to become semi- spherical as globules.
That is as dense as it is possible naturally. 1cc = 1g @ 20°C at 1 atmosphere.
If the energy in the molecules is reduced further either mechanically or naturally, the molecules will change state. An enormous amount of energy is required. It is quantified as the Specific Heat Capacity. There are two ranges:
- 'Latent Heat' - Changes the state of the molecules from liquid to solid, or liquid to gas. There is no temperature change though. The changes occur at 0°C (freezing) and 100°C (boiling).
- 'Sensible Heat' - Energy will cause the molecules to increase or decrease in movement increasing or decreasing in temperature.
Water is unusual. When it becomes frozen it decreases in density. Ice floats on water. Other substances normally become more densely packed as the temperature falls.
Gas as the Americans call petrol is an example of it being a liquid at low temperatures. It can also be gas at relatively low temperatures. Spill petrol down the side of the car when filling it. The petrol within seconds will evaporate into gas. It is termed a 'volatile liquid'
Other gases such as methane and propane become liquified when their volume is reduced. The temperature also falls when they become liquified. A change in pressure regulates the molecular state. The more pressure means the atoms and molecules in gaseous state cannot move about so much. They bounce off the container walls and cannot collide with the same velocity. Less heat is produced. The gas becomes a liquid when under pressure below atmospheric pressure.
In cold weather if the gas bottles or pipes that transport the liquid gases to become gases again energy is required. For example a gas hob used in a caravan.
The liquified gas requires a lot of energy to become gas again. The energy is taken from the energy in the air.
Air naturally contains H2O molecules. As previously mentioned, when they are cooled down they become condensation and if cooled further become ice.
Ice formed from air molecules is termed 'frost'. That is what forms on the pipes and bottles as the liquified gas becomes gas again.
- Heat is the product of molecular collisions, mainly the electrons colliding
- No atoms = no heat
- No atomic movement = no collisions = no heat = Absolute Zero