Summary Section 2: Thermal Physics

Section 2:
Thermal Physics


Thermal Energy Transfer

The Absolute Temperature Scale:

 The lowest possible temperature that any object can theoretically have is the absolute zero –
around 273 ͦC or 0Kelvins.
o At this temperature, all molecules have zero kinetic energy
𝐾 (𝐾𝑒𝑙𝑣𝑖𝑛) = 𝐶 (𝐷𝑒𝑔𝑟𝑒𝑒𝑠) + 273

Internal Energy of a gas:

 The Internal energy of a body is the sum of the randomly distributed kinetic and potential
energies of all its particles.
o Gas have potential energy too
(unless it’s an ideal gas)

 Gas particles don’t all travel at the
same speed; the speed distribution of
gas particles depends on the
temperature.
o Though most particles will be
an average speed, some will be
greater or smaller as well.

As temperature increases:

1. The average particle speed increases
2. The average kinetic energy of the
particles increases
3. The distribution curve becomes more spread out

Energy changes between particles:

 Closed systems
o One which doesn’t allow any transfer of matter in or out. As long as the system isn’t
heated or cooled, the total internal energy will stay the same.

Within a system:

 Energy is constantly transferred between particles in a system through collisions, but the total
internal energy is the same.
o Therefore, the average speed of each particles will remain the same, provided it’s a
closed system