What do the laws of thermodynamics say

Thanks to this unavoidable touch of randomness — or what's known as entropy — a closed system will always creep towards a uniformly disordered state. You can shuffle in more energy to recreate some unique bits of order, but remember, the Universe isn't getting a fresh supply of useful energy, and in the end, everything will be the same old, useless heat filtering out into the icy depths of expanding space.

This inevitable slide into a chaotic state is the increase of entropy. Maximum entropy would occur when all the energy in the Universe is uniformly spread out. This is known as heat death or, if you're a dramatic type, the Big Chill and could be the ultimate fate of the Universe. This approach also led to the conclusion that while collisions between individual molecules are completely reversible, i. The result of this is that when hot gas and cold gas are placed together in a container, you eventually end up with warm gas.

However, the warm gas will never spontaneously separate itself into hot and cold gas, meaning that the process of mixing hot and cold gasses is irreversible. One thing the Second Law explains is that it is impossible to convert heat energy to mechanical energy with percent efficiency. After the process of heating a gas to increase its pressure to drive a piston, there is always some leftover heat in the gas that cannot be used to do any additional work. This waste heat must be discarded by transferring it to a heat sink.

In the case of a car engine, this is done by exhausting the spent fuel and air mixture to the atmosphere. Additionally, any device with movable parts produces friction that converts mechanical energy to heat that is generally unusable and must be removed from the system by transferring it to a heat sink.

This is why claims for perpetual motion machines are summarily rejected by the U. The system and surroundings are separated by a boundary. For example, if the system is one mole of a gas in a container, then the boundary is simply the inner wall of the container itself. Everything outside of the boundary is considered the surroundings, which would include the container itself. The boundary must be clearly defined, so one can clearly say whether a given part of the world is in the system or in the surroundings.

If matter is not able to pass across the boundary, then the system is said to be closed ; otherwise, it is open. A closed system may still exchange energy with the surroundings unless the system is an isolated one, in which case neither matter nor energy can pass across the boundary. The first law of thermodynamics, also known as Law of Conservation of Energy, states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another.

For example, turning on a light would seem to produce energy; however, it is electrical energy that is converted. Spontaneous processes do not require energy input to proceed, whereas nonspontaneous processes do. There are two types of processes or reactions : spontaneous and non-spontaneous.

Spontaneous changes, also called natural processes, proceed when left to themselves, and in the absence of any attempt to drive them in reverse. The sign convention of changes in free energy follows the general convention for thermodynamic measurements. This means a release of free energy from the system corresponds to a negative change in free energy, but to a positive change for the surroundings.

Examples include:. The laws of thermodynamics govern the direction of a spontaneous process, ensuring that if a sufficiently large number of individual interactions like atoms colliding are involved, then the direction will always be in the direction of increased entropy. This does not contradict the second law, however, since such a reaction must have a sufficiently large negative change in enthalpy heat energy. The increase in temperature of the reaction surroundings results in a sufficiently large increase in entropy, such that the overall change in entropy is positive.

Spontaneity does not imply that the reaction proceeds with great speed. For example, the decay of diamonds into graphite is a spontaneous process that occurs very slowly, taking millions of years. The rate of a reaction is independent of its spontaneity, and instead depends on the chemical kinetics of the reaction. Every reactant in a spontaneous process has a tendency to form the corresponding product.

This tendency is related to stability. An endergonic reaction also called a nonspontaneous reaction or an unfavorable reaction is a chemical reaction in which the standard change in free energy is positive, and energy is absorbed.