3.1 Thermal concepts Flashcards
What is the absolute temperature scale?
A temperature scale on which the lowest possible temperature is zero degrees. The absolute and celsius scale are related by +273.
What is the average random kinetic energy of molecules?
The average random kinetic energy of the molecules of a substance is proportional to the absolute temperature of the substance:
1/2mv^2 = 3/2kT where k is the Botlzmann constant. At T=0K the random kinetic energy of the molecules is therefore zero.
What is internal energy?
The total random kinetic energy of the molecules of a system plus its total intermolecular potential energy.
What are intermolecular forces?
There are forces, electromagnetic in origin, between any two molecules in any substance whether solid, liquid or gas. These forces are strongest in the solid phase and weakest in the vapour phase. Because of these forces increasing the separation of molecules requires that work be done the work increases the intermolecular potential energy and hence the internal energy of the substance. For an ideal gas these forces are zero and so internal energy only consists of the random kinetic energy of the molecules.
What is heat?
Energy that is transferred from one body to another due to a difference in temperature.
What is the direction of energy flow?
Heat always gets transferred from a higher temperature to a lower temperature region.
What is thermal equilibrium?
When two bodies are at the same temperature they are said to be in thermal equilibrium and no further net energy gets transferred between them.
What is an ideal gas?
A theoretical model in which there are no intermolecular forces between the particles of the gas and so no intermolecular potential energy in its internal energy. An ideal gas obeys the equation pV=nRT at all pressures, volumes and temperatures. Real gases obey the gas law approximately and only for a range of pressures, volumes and temperatures.
What is a mole?
The SI unit for quantity. One moles of any substance contacts Na = 6.02x10^23 molecules, this number is known as the Avogadro constant.
What is molar mass?
The mass in grams of one mole of a substance.
