Scientific Sunday#5- Thermodynamics

Thermodynamics

Fire and heat are one of the if not the best source of energy. They are the primordial form of energy. The term thermodynamics was Greek for heat and power. The discovery of fire is like a milestone for the human race, it essentially ensures and speeds up the growth of the human civilization. Without fire, many things wouldn't have happened. In science thermodynamics describes the relationship of heat to work. Heat is not something that an object contains. It is a flow of energy: temperature simply measures an object's ability to transfer heat energy to another object or system. For example: The hot water in a tub is full of high energy molecules that can move their energy to the bathing person's cooler body. Entropy, a key concept in thermodynamics, is the proportion of thermal energy that is unavailable for such work due to the random motion of particles.

SECOND LAW OF THERMODYNAMICS

The second law of thermodynamics describes the natural process of energy, while energy can neither be created or destroyed, it does change form. Real-world processes invariably end up with less energy that can do work since they used up their potential energy, so entropy increases.

For example: an engine converts chemical energy, lets say gasoline, into motion and heat. When the gasoline runs out, the engine stops. A firework explodes with the force of expanding gases, after which its usable energy is dissipated. The process doesn't run in reverse. Similarly, heat energy always moves from hot things to cold, never the other way round. A mug of hot coffee will transfer thermal energy to its cooler surroundings until the coffee and surrounding reach what's called thermodynamic equilibrium- both the surroundings and coffee are at the same temperature. The system retains the same amount of energy overall, but its usable energy is spent. 

An Air-conditioner

One of the many machines that applies thermodynamics is the savior of people who live in tropical countries: Air-conditioners. But how much do you know about how these things work? Rather than saying that an air-conditioner gives out cold air to cool the room, it would be more accurate to say that it removes the heat from the room.  To fully understand it, you must understand the state of matter is related to temperature. Heat up an ice cube it melts, apply 100C or more heat to water and it evaporates. Similarly, withdraw heat from gas and it liquefies, withdraw from liquid and it freezes. 

Air conditioning works by forcing a chemical called Freon to cycle between liquid and gas forms. The reason why Freon is an ideal choice is because it has a very low boiling point, since the bond between its molecules is weak. Inside an air conditioner, Freon is kept in a tube at very high pressure and then released through a valve into a low-pressure evaporator.  With no pressure pushing them together, Freon molecules boils and vaporizes. As I had stated earlier, changes of states of matter require heat, so Freon will takes the heat from air the room. After doing so, Freon passes to a compressor which pushes the molecules back together and into the condenser tube, where it liquefies. The heat associated with vaporizing is lost and released outdoors. Now, the process repeats again.

A Refrigerator

A machine similar to the air-conditioner, a refrigerator keeps your food fresh and cold drinks cold.  Both air-conditioners and refrigerators were developed around the early 20th century. Refrigerator enter the world to tackle a more pressing problem: food spoilage. Before refrigerators, people kept their food cold using an insulated box containing a hunk of ice. Modern day refrigerators combines the ice box with the same technology used in 
air-conditioning. 

A refrigerant fluid is made to vaporize via a change in pressure, absorbing heat from inside the fridge, and then condenses in a condenser tube, and releases the heat outside the refrigerator. Both the refrigerator and the air-conditioner use pressure differences to promote vaporization and condensation. The work overcame a law-governing natural processes: that heat can never flow from a cooler zone to a hotter one.

Thanks for reading