What are the 1st and 2nd Laws of Thermodynamics?

Question

I'm looking for them in Lamens terms, naturally. I want to know because I have a big Physics and Chem. test to take, and I have no IDEA what they are and there are all sorts of questions about it.

Answer 1

1st law=nothing can be created or destroyed, only re-arranged.

2ND law energy travels in one direction as heat and can not be captured for usage which lends to an increase of entropy.

Answer 2

First law

“ In any process, the total energy of the universe remains constant. ”


More simply, the First Law states that energy cannot be created or destroyed; rather, the amount of energy lost in a steady state process cannot be greater than the amount of energy gained.

This is the statement of conservation of energy for a thermodynamic system. It refers to the two ways that a closed system transfers energy to and from its surroundings - by the process of heating (or cooling) and the process of mechanical work. The rate of gain or loss in the stored energy of a system is determined by the rates of these two processes. In open systems, the flow of matter is another energy transfer mechanism, and extra terms must be included in the expression of the first law.

The First Law clarifies the nature of energy. It is a stored quantity which is independent of any particular process path, i.e., it is independent of the system history. If a system undergoes a thermodynamic cycle, whether it becomes warmer, cooler, larger, or smaller, then it will have the same amount of energy each time it returns to a particular state. Mathematically speaking, energy is a state function and infinitesimal changes in the energy are exact differentials.

All laws of thermodynamics but the First are statistical and simply describe the tendencies of macroscopic systems. For microscopic systems with few particles, the variations in the parameters become larger than the parameters themselves, and the assumptions of thermodynamics become meaningless. The First Law, i.e. the law of conservation, has become the most secure of all basic laws of science. At present, it is unquestioned.


Second law

“ There is no process that, operating in a cycle, produces no other effect than the subtraction of a positive amount of heat from a reservoir and the production of an equal amount of work. ”


This version is the so-called Kelvin-Planck Statement. In a simple manner, the Second Law states that energy systems have a tendency to increase their entropy (heat transformation content) rather than decrease it.

In simple terms, it is an expression of the fact that over time, differences in temperature, pressure, and density tend to even out in a physical system which is isolated from the outside world. Entropy is a measure of how far along this evening-out process has progressed.

The entropy of a thermally isolated macroscopic system never decreases (see Maxwell's demon), however a microscopic system may exhibit fluctuations of entropy opposite to that dictated by the Second Law (see Fluctuation Theorem). In fact, the mathematical proof of the Fluctuation Theorem from time-reversible dynamics and the Axiom of Causality, constitutes a proof of the Second Law. In a logical sense the Second Law thus ceases to be a "Law" of Physics and instead becomes a theorem which is valid for large systems or long times.

Stephen Hawking described this using time as an entropy base. For example, when time moves in a forward direction and one, say, breaks a cup of coffee on the floor, no matter what happens, in our universe, one will never see the cup reform. Cups are breaking all the time, but never reforming. Since the Big Bang, the entropy of the universe has been on the rise, and so the Second Law states that this process will continue to increase.

Answer 3

The first law of thermodynamics is: The increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings.

The second is: The inevitable tendency of things to degrade, fall apart, cool down or lose momentum, also known as entropy.

Answer 4

The first law means that you cannot simply make energy you can only change it. For instance changing potential energy into kinetic energy. Once it has changed you still have the same amount you started out with.
The second law means that if a spontaneous process occurs there will be an increase in the entropy of the universe.

Answer 5

1st Law: Energy basically has always been on earth. It is not created nor destroyed. Energy, instead, takes on many forms. It changes instead of being created. It is constant. Heat is involved. http://www.chemistry.ohio-state.edu/~woodward/ch121/ch5_law.htm

2nd Law: Basically the process of one extreme to the other and the evening out of both...as well as the length of time it takes....
http://en.wikipedia.org/wiki/Second_law_of_thermodynamics

Answer 6

See link below.