True or false: the second law of thermodynamics says that the entropy of a system cannot spontancously decrease.

It is true only if we consider an isolated system

Explanation:

The second law of thermodynamics requires that, in general, the total entropy of any system cannot be reduced except by increasing the entropy of some other system. Therefore, in a system isolated from its surroundings, the entropy of that system tends not to diminish. It follows that heat cannot flow from a colder body to a warmer body without the application of work (the imposition of order) to the colder body.

Secondly, it is impossible for a device that operates in one cycle to produce network work from a single temperature reservoir; Network production requires heat flow from a hotter tank to a colder tank, or a single expanding tank undergoing adiabatic cooling, which performs adiabatic work. As a result, there is no possibility of a perpetual motion system.

It follows that a reduction in the increase in entropy in a specific process, such as a chemical reaction, means that it is more energy efficient.

It follows from the second law of thermodynamics that the entropy of a system that is not isolated can decrease. An air conditioner, for example, can cool the air in a room, thus reducing the entropy of the air in that system. The heat expelled from the room (the system), which the air conditioner carries and discharges to the outside air, always contributes more to the entropy of the environment than the decrease in the entropy of the air of that system. Therefore, the total entropy of the room plus the entropy of the environment increases, according to the second law of thermodynamics

pre-sliced bread is a relatively recent development in baking technology. previous to that, it was always sold in a bakery in daily-made contiguous loaves with no wrapping, and was moderately perishable, usually being used with a day or two (which is why every bakery had a discounted “day-old” bread table.) therefore, pre-sliced bread would grow stale quickly. the hard crust provided a protective layer, and once the exposed dry slice left from the previous cut was removed, the interior was still soft.

what keeps bread soft is the moisture retained in the crumb (the light spongy part that’s not crust). the reason the crust develops is the surface of the dough gets exposed to hot dry air during baking which browns the outer layer and seals it, preventing all the moisture from escaping the dough. longer exposure to air will also eventually cause your bread to lose flavor and become stale.

people were used to cutting slices as they needed them and storing bread in a specially-made wooden or metal breadbox or pail with a lid to preserve it longer, but the first automatically sliced commercial loaves were produced on july 6, 1928, in chillicothe, missouri, using a machine invented by otto rohwedder, an iowa-born, missouri-based jeweler.[1] pre-sliced bread would indeed dry out, were it not for another 20th century technology: the plastic bag. bread could now be pre-sliced, and if the enclosing bag remains sealed as much as possible, the bread will remain soft and fresh for longer than if sitting unwrapped on a shelf or enclosed in a bread box that is not air-tight. sealed packaging meant bread could also be sold on store shelves and eliminate frequent trips to a bakery.

sealing bread in a plastic bag had another effect: the moisture in the loaf will re-distribute into the crust and soften it, which is sometimes more pleasing in a sandwich - especially for children whose teeth might not yet be strong enough to tear through a hard crust. a homemade loaf of bread can be sealed in a bag overnight and the crust will become soft like store-bought sandwich bread.

these were novel changes in how bread was produced and sold, which led to the coining of the phrase “the greatest thing since sliced bread.”