Watt’s in a Name?

James Watt is a name I am sure that I had heard somewhere along my academic career (I mean, he has a unit of power named after him), but he is a (justifiably) big deal around here.  There was an entire floor of the Science Museum here in London devoted to the engineering and rise of steam power and he is at the center of that.  We are talking a recreation of his workshop space, no fewer than 10 busts of him, various scaled versions of his steam powered gadgetry, and much more.  So, while it was not on my radar of things to be looking out for in London, I find myself in need of a blog post on steam.

But first, a little chemistry background. As many of my students know, water is my favorite chemical compound.  H₂O.  If you learn one thing from a chemistry class, as my colleague Sarah Bauer always says, it should be that water is polar (and, arguably, PV=nRT, which is also related to steam power!).  The polarity of water is responsible for its many unique and useful characteristics.  A polar molecule has one side that is slightly negative and one side that is slightly positive (2 poles, like the +/- poles of a battery or the 2 magnetic poles of the earth).  This is due to the 3-D shape of the molecule (the highly scientific “bent” geometry – no one ever said scientists were the most creative when it comes to naming…) and the electron cloud on the molecule being shifted more toward the oxygen because of oxygen’s greediness for electrons. 

These poles on the molecule cause it to be attracted to another just like it – the partial positive (δ+) on the one to the partial negative (δ-) on the other.  This stickiness to itself is called cohesion and is a specialized intermolecular force (force of attraction between two molecules) called hydrogen bonding, which is quite strong and can only happen between molecules with certain shapes and combinations of atoms.  This allows for many of the important characteristics of water, including its ability to absorb a lot of energy without drastically changing its temperature.  This is called its heat capacity, or specific heat.  An increase in temperature causes molecules of water to move around, which weakens those hydrogen bonds and ultimately allows them to go from the liquid phase to the gas phase. But, it takes a lot of energy to do that.

An engine is a machine that drives a process by converting one form of energy into another. Steam engines use some combination of 1) the energy from this phase change of water from liquid to a gas (∆H_vap, for those who have some chemistry background), 2) the pressure that is built up from that gaseous form of water, and/or 3) the vacuum that is produced from the difference in pressure created by that water vapor in order to do mechanical work (driving pistons that can be connected to rods that can move pumps – if you ever played the game Mousetrap as a kid, that’s always my vision).  This is different than a gasoline combustion engine, which is chemical work doing mechanical work.  In that, we get different products than we start with.  Hydrocarbons and O₂ in, CO₂ and water out.  Phase changes – like going from liquid to gas (evaporation or vaporization) – are not chemical changes.  Water is still H₂O, whether it is in the liquid phase or the gas phase.  That change from liquid to a gas requires energy, though – think heating up a pot of water to cook your pasta (and how long that takes! That’s that high heat capacity!) – and results in a physical change.  A physical change (or thermal (heat) energy) produces mechanical work.  Pretty ingenious.  “And so clean!”, you think.  But, how did the water get heated?  You guessed it: coal burning.

One of the earliest practical steam engines was built in 1712 by Thomas Newcomen (1663-1729).  The Newcomen engine was not very powerful nor was it very efficient, but it was interesting because it could transmit continuous power to whatever machine it was powering, meaning that it allowed for the process to be ongoing whereas the use of steam in the past relied on single instances (starts and stops) of heating water and utilizing the steam to do work. His design allowed miners to pump water up from mines and relied not on the pressure from the build up of steam, but in the vacuum created by the difference in pressure of the water vapor as compared to the atmospheric pressure.  It was called an atmospheric engine because the pressures that were produced during its functioning were around atmospheric pressure (1 atm, 760 mmHg, 101.3 kPa).

This image above is from a great site through Michigan State University that dives much more into the history and inner workings than I do here – highly recommend checking it out.

After a couple of versions of this (again, recommend that site linked above, if you are interested in the development in more detail), James Watt (1736-1819) came along and optimized it in 1764 (so young!). He is often listed with his partner, and his partner, Matthew Boulton (1728-1809), who was also an inventor, but really helped with the business side of things.  Their engines were atmospheric engines, as well, but they evolved into something that could drive more complicated apparatus with less fuel burned (the internet says the plural for apparatus is apparatus…or apparatuses…but, I really wanted it to be apparati). One of their more famous engines was what I can only assume was affectionately known as ‘Old Bess’.

Old Bess is an atmospheric (utilizing pressures close to our atmospheric pressure), beam (pistons are used to move a beam, which acts as a pump) engine. Because we are talking pressures around atmospheric pressure, you can see that there were still counterweights needed to assist in moving the beam/pumping mechanism. You can also see from the parts that still exist from this engine today (found, again, at the Science Museum in London in the Energy Hall) that it is massive (humans in background of photo for scale).

So, Watt’s major contribution: increased efficiency and less fuel needed to to more work. He had a love of tinkering and found inspiration from every day objects (there’s a lovely wives’ tale about Watt being inspired by a tea kettle). His work pulled the steam engine and England into the Industrial Age.  This technology was used to power factories and the impact on transportation cannot be overstated.  Think about going from paddles and sails to steam power!  Trains, too, became steam powered at the beginning of the 19^th century.  Game changer. 

Watt, specifically, is recognized for these contributions – I saw the memorial stone for him at Westminster Abbey (he is not buried there, but there are many memorials there to people of historical significance throughout England’s history).  It says (in case you cannot see with the lighting in my photo above, but full text is below), “The King, [et al.]…Raised this Monument to JAMES WATT Who, directing the force of an original Genius early exercised in philosophic research to the improvement of The Steam Engine, Enlarged the resources of his Country, Increased the power of Man, And rose to an eminent place among the most illustrious followers of science and the real benefactors of the World.”  Whoa.

Not to perpetuate a name, which must endure while the peaceful arts flourish, But to show that mankind have learned to know those who best deserve their gratitude.  The King, His Ministers, and many of the Noble and Commoners of the Realm, Raised this Monument to JAMES WATT Who, directing the force of an original Genius early exercised in philosophic research to the improvement of The Steam Engine, Enlarged the resources of his Country, Increased the power of Man, And rose to an eminent place among the most illustrious followers of science and the real benefactors of the World.

Text from Watt memorial stone, Westminster Abbey