Energy+and+Thermal+Transfer


 * Energy and Thermal Transfer**


 * Existing course days: ||  || Key resources ||
 * Heat and other energy transfers ||  || SPT materials produced by the IOP can be found and downloaded for free from talk physics ||
 * Thermal properties ||  || Also available through the IOP is the TAP materials. ||
 * Thermodynamics ||  || This is interesting - [|energy pathways calculator] from DECC. ||
 * Kinetic Theory || ................. ||  ||

Probably one of the harder ideas to get your head around as a non-specialist. The biggest challenges here are the abstract nature of the topic. The National Curriculum has been simplified to the point that students (and, to an extent, teachers) have undergone Pavlovian conditioning to want easy answers. There is no simple, pithy answer to the question: "What is energy?" In addition, the misuse of terminology (Dr Who writers, hang your heads) and the use of terms in common parlance creates barriers to understanding.
 * Teaching notes.**

Common misconceptions abound: the idea that energy can be 'used up', that it is a kind of 'stuff', that energy causes things to happen - all of these need to be recognised and challenged explicitly. Teachers have some odd ideas about energy too and the curriculum, SATS questions and textbooks haven't helped. The idea that there are separate, compartmentalised 'forms' of energy is counter-productive. Rather than thinking of energy 'changing forms' students should consider the means by which energy is transferred. The IOP, via the SPT materials, advise teachers to consider energy 'stores' and 'pathways' - a helpful concept although personally I try to be careful when introducing more non-everyday vocabulary to the topic - students have a tendency to fixate on them as magic words and will throw them into an explanation like sprinkling fairy dust. The important thing is understanding the means by which energy is transferred and being able to describe it clearly. Feynman's quote gives us a good idea of the difficulty inherent in introducing the topic even as it suggests a way forward:

"There is a fact, or if you wish, a law governing all natural phenomena that are known to date. There is no known exception to this law – it is exact so far as we know. The law is called the conservation of energy. It states that there is a certain quantity, which we call “energy,” that does not change in the manifold changes that nature undergoes. That is a most abstract idea, because it is a mathematical principle; it says there is a numerical quantity which does not change when something happens.  It is not a description of a mechanism, or anything concrete; it is a strange fact that when we calculate some number and when we finish watching nature go through her tricks and calculate the number again, it is the same.  It is important to realize that in physics today, we have no knowledge of what energy “is.” We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. It is an abstract thing in that it does not tell us the mechanism or the reason for the various formulas."

Use of language and construction of explanations is vital here - remember that language shapes thought as well as vice-versa so get your students to explain simple phenomena as much as possible, using misconception-challenging constructions - "The car is moving, so we can calculate its kinetic energy" instead of "The car moves because it has kinetic energy". The simplest items can be used to discuss ideas about energy transfer, toys, candles, household items - if you're going to buy any bit of pricey kit for this topic the SEP energy meter is a good one. An unforgettable demonstration of the principle of conservation of energy is the giant pendulum - do the risk assessment! The question of 'energy loss' is a good one - get into the idea of defining a system - it lays a good foundation for talking about efficiency and things like Sankey diagrams. Your students are going to have to get into doing calculations at some stage. As usual, the advice is to make sure that the concepts are sound before diving into the maths! Where there are sums to be done, avoid the triangles and do the algebra - link the sums to the units, too, so that the units make sense as part of the whole scheme.