What happens during change of state? The following figures are for the standard entropy of water in different states. These all have low entropies because they are highly ordered solids, but notice that the entropy usually increases as the solid gets more complicated. Here are some standard entropies for a few solids, all with the units J K -1mol -1: carbon (as diamond) Use whatever units the examiners give you. 1 bar is 100 kPa 1 atmosphere is 101.325 kPa. Don't worry about it - they are nearly the same. You might find the pressure quoted as 1 atmosphere rather than 1 bar in older sources. This includes solid to liquid, liquid to gas and solid to aqueous solution.Д®ntropy is given the symbol S, and standard entropy (measured at 298 K and a pressure of 1 bar) is given the symbol SВ°. If you look in textbooks or on the web, you will find explanations of increasing difficulty - some very scary indeed! Don't waste time on these at this level. 'a system becomes more stable when its energy is spread out in a more disordered state'. The entropy has increased in terms of the more random distribution of the energy. The faster moving particles have more energy the slower ones less. After a very short time, their arrangement in space will be chaotic, and so will the way energy is shared between them. And then you let them go and do what molecules do - move around, and bump into each other and the walls of the container.Д®ach collision between two molecules will cause them to change direction, and it will probably speed up one of them, and slow down the other. Suppose you managed to arrange some gaseous molecules in a container so that they were all exactly evenly spaced and so that they all had exactly the same energy - a fairly ordered state. A system which is more disordered in space will tend to have more disorder in the way the energy is arranged as well. But we often just quickly look at how disordered a system is in space in order to make a judgement about its entropy. Technically, entropy applies to disorder in energy terms - not just to disordered arrangements in space. Now, it is just imaginable that when you dropped them, by chance they would fall into a neat stack of coins like the one you started with, but the probability of that happening, compared to all the other ways that the coins might fall, is so very, very tiny that you would be totally amazed if it happened. Every time you did this, you would get a different random pattern of coins on the floor - arranged just by chance. That's a fairly ordered state for them to be in.

Suppose you held a stack of ten coins between your finger and thumb. We now expand on this a bit, but luckily not too much! Let's look at this with a couple of thought experiments.

A very disordered system (a mixture of gases at a high temperature, for example) will have a high entropy.

A very regular, highly ordered system (diamond, for example) will have a very low entropy.

This page provides a simple, non-mathematical introduction to entropy suitable for students meeting the topic for the first time.ДЄt this level, in the past, we have usually just described entropy as a measure of the amount of disorder in a system.

Entropy disorder