QUESTION #205

# Books say that heat transfer in an adiabatic process is equal to 0. How can this be if there is a change in temperature?

Asked by: Miguel Angel

### Answer

You are probably making the common mistake among students by not realizing that heat and temperature are two completely different things.

Heat is a quantitative measurement of energy whereas temperature is a qualitative measurement which indicates the warmth or coldness of an object.

In an adiabatic process, there is no heat transfer to or from the system, and therefore change in entropy = 0. Temperature, however, can increase or decrease despite the lack of heat flow. For example, take an insulated piston cylinder device containing some arbitrary gas (common example in thermodynamics problems). If you were to push the piston down (thus compressing the contents of the cylinder), the temperature of the gas in the cylinder would increase. If the piston was pulled out (thus expanding the gas) the temperature would decrease. In either case, no heat would flow to or from the system, but the temperature would change approximately according to the relationship PV=nRT (for the most general cases)
Answered by: Jeff Hartnett, Mechanical Eng./Mathematics Undergrad Student