Monday, 29 April 2013

Entropy



Back to "sanity" then:

Click to tweet: http://clicktotweet.com/1Ln65  .  Exothermic reactions generate heat.  The example i use here doesn't work very well and you're just going to have to take my word for it that it got warmer.  Sodium hydroxide added to water (NOT THE OTHER WAY ROUND, WHICH WOULD WORK BUT IS DANGEROUS!) makes the water hotter when it dissolves.  Other examples:  anhydrous copper sulphate heats water when added to it, and combustion is the exothermic reaction par excellence - the combination of oxygen with many different compounds and elements generates heat, a process known as burning.

The human body, along with those of other mammals, all birds, flying insects and a few species of bony fish, also has exothermic reactions going on inside it which generate heat, which is why we're not the same temperature as our surroundings.  Rather confusingly, this is known in biology as endothermy rather than exothermy (or the confusion could be the other way round depending on your perspective) and the more common phenomenon of being warmed and cooled by the environment, as found in lizards and most other organisms other than insects and some vertebrates, is known by the almost as confusing name of ectothermy.

This brings me to the second type of process:  endothermic reactions and processes.  These are processes which absorb heat from their environments.  A very common but difficult to observe example is found when sodium chloride - ordinary table salt - dissolves in water.  This process, leaving other things aside, would very slightly cool the water, or rather, the solution that results from sodium chloride and distilled water at the same temperature will be slightly cooler than either.  This is because work is done breaking up the salt into ions, combining them with water and breaking the hydrogens off from the water molecule.  Another, rather neat, example is photosynthesis, which is the synthesis of the sugar glucose from water and carbon dioxide with the help of light.  Again this is slightly cooling, unlike the opposite process of respiration, which is the release of energy stored in glucose, often with the aid of oxygen, which is exothermic, though only mildly so.  For some reason it's much easier for me to think of non-chemical processes which are endothermic than chemical ones.  Fridges generally use the same process as the one i illustrate in this video, which is the evaporation of a liquid which removes heat from a system, in this case tincture of myrrh (Commiphora molmol), which is 90% alcohol (ethanol in fact) evaporating from the palm of my hand.  Incidentally, this is also an example of osmosis, as water was pulled from my hand across the concentration gradient caused by the 90% ethanol. The same happens with rubbing alcohol (isopropanol).




This is not part of the description but a test.  Please, if anyone at all reads these entries, could you leave me a comment?  I'm pretty sure nobody does but if i put this at the top, you'd see it on your feed, so it's here.  Thanks.

Enthalpy, which i can't pronounce, is a measure of the total heat or energy in a system.  It can be calculated by the equation H=U+PV, or enthalpy in joules per mole is equivalent to the total energy of the system in joules per mole plus the pressure in newtons per square metre multiplied by the volume in moles per cubic metre.  In fact, Delta-H is a more useful quantity because the real total energy of a system is vast - see zero-point energy for example.  Delta-H is the change in total energy.  I show the concept of total energy by blowing up a balloon.  The balloon is inflated with five litres of air at my body temperature, but as it enters the balloon, because of the elasticity of the rubber it becomes compressed and will therefore start at above body temperature.  The system contains the same amount of energy as the system of the air in my lungs after inhaling, but in a smaller space.  The potential energy is also clear because of the energetic deflation of the balloon, although this is merely mechanical.  That could, however, be generated by heat if the balloon was warmed.

A bomb calorimeter is a way of assessing the usable chemical energy in a sample.  The sample is ignited and the heat released is measured.  This is useful for food and other substances such as fuel or explosives.  A calorie (small c) is the energy required to raise a gramme of water by one degree Centigrade/Kelvin/Celsius, a unit which is not very useful for measuring the energy of food, for which reason Kilocalories (usually referred to as "Calories", with a big C) are used.  However, both have been superceded by joules.

Please note that i wasn't particularly safe with how i handled the caustic soda.


To be honest, this could've had more detail on the maths side of things but i'm afflicted by the problem of not really understanding enthalpy, or for that matter even pronouncing it.  However, i did what i did with it and in fact the bigger problems are not so much the subject matter as  the excessive length of these videos and trying to come up with a title that's both catchy and brief.  The thumbnail's quite nice though, except that it looks like the logo for a band.

For the first time, my subscribers on both the main and Other Channel are equal.  The Other Channel grew from about ten dozen and nine slowly over the past few weeks and the main channel has jumped rather faster.  I now have eleven dozen and four subscribers on each.  However, as usual i'm experiencing the paradoxical issue of views going down as subscribers go up.  I think this is connected to consistency of content.  When i see a jump in views, i tend to concentrate on the subject area of the latest upload for a while, and that may encourage subs but make the content less diverse and therefore other subscribers, who subscribed for different reasons, are less likely to watch.  I'm pretty sure the diversity of content is the biggest factor in keeping views and subs down, but presumably the people who have subscribed are keen on both the diversity and frequency of posting.  On another matter, i think people are encouraged to sub by the other channels but put off by the very different content. Whereas i occasionally stray into the areas covered by the other channels, it's not frequent.  In a way, Handsonisbetter is where the educational videos should be, but that has such a tiny number of views and subs that it's not worth it.

I'm going to talk about Nyarlathotep openly now, so if anyone really is reading this you're going to think i'm a sad bastard who has gone nuts. 

I have considerable insight into why it happened and realise she is to some extent not in control of what happened, and i'm over it, but in a way i'm not.  This is because i am aware of the massive swerve my life has taken whereas most other people aren't, and i also think that she of all people should be in a position to understand that.  So i'm going to continue to make occasional bizarre references to her because on some level i am still just really, really pissed off and i don't think that will ever end.  I think people who work in the caring professions have no right to do so unless they are able and willing to empathise with outsiders, and actually choosing to place them there and keep them there is completely crap.  I realise it's a pretty minor problem compared to most of what many people have to deal with, including me, but it's an unscratchable itch and i am not going to let it go.

Nyarlathotep, you who will never read this, i valued our friendship above whatever else was going on and i think it's sad that you're unwilling to rise above that.  Have you ever wondered what direction things would've gone in for you if you'd just been a little bit more real about it?