Minus-oneth law,

Such statements concerning the direction of heat transfer are sometimes called the minus-oneth law of thermodynamics, which sounds rather daunting. In fact, the word thermodynamics here may be taken apart piecemeal to translate it into everyday English. 

The minus-oneth law of thermodynamics says, heat always travels from hot to cold. ... 

We need to explain the bizarre name of this law, which is really an accident of history. Soon after the first law of thermodynamics was postulated in the mid nineteenth century, it was realized how the law presupposed a more elementary law, which we now call the zeroth law (see below). We call it the zeroth because zero comes before one. But scientists soon realized how even the zeroth law was too advanced, since it presupposed a yet more elementary law, which explains why the minus-oneth law had to be formulated. 

The energy transferred during an inelastic collision passes from the hot molecule of steam to the cooler mirror. This energy flows in this direction because the steam initially possessed more energy per molecule than the mirror as a consequence of its higher temperature. It is merely a manifestation of the minus-oneth law of thermodynamics, as discussed in Chapter 1. 

The evidence for such a transfer of energy between the mouth and the ice cream is the change in temperature, itself a response to the minus-oneth law of thermodynamics (p. 7), which says heat travels from hot to cold. Furthermore, the zeroth law (p. 8) tells us energy will continue to transfer from the mouth (the hotter object) to the ice cream (the colder) until they are at the same temperature, i.e. when they are in thermal equilibrium. 

The example above illustrates how energy flows in response to the minus-oneth law of thermodynamics, to achieve thermal equilibrium. The impetus for energy flow is the equalization of temperature (via the zeroth law), so we say that the measurement is isothermal. 

In previous chapters we looked at the way heat travels from hot to cold, as described by the so called minus-oneth law of thermodynamics, and the way net movements of heat cease at thermal equilibrium (as described by the zeroth law). Although this transfer of heat energy was quantified within the context of the first law, we have not so far been able to describe why such chemical systems occur. Thermodynamic changes only ever proceed spontaneously in one direction, but not the other. Why the difference ... 

Let us return to the assertion that q is zero, which implies that the system is energetically closed, i.e. that no energy can enter or leave the tyre. This statement is not wholly true because the temperature of the gas within the tyre will equilibrate eventually with the rubber of the tyre, and hence with the outside air, so the tyre becomes cooler in accordance with the minus-oneth and zeroth laws of thermodynamics. But the rubber with which tyre is made is a fairly good thermal insulator, and equilibration is slow. We then make the good approximation that the system is closed, energetically. We say the change in energy is adiabatic. 

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