Rising air cools as a result of a decrease in barometric pressure with altitude. (Lapse Rate) True/False?
When an inflatable life jacket is inflated with a compressed air cylinder the air inside the now inflated life jacket is much colder than it was prior to inflation when it was still compressed inside the cylinder. The air is colder because it is now under less pressure as per the air in question 1. True/False?
When a Carbon Dioxide fire extinguisher is discharged the nozzle often freezes. This is as a result of the reduction in pressure. True/False?
If you were to place a thermometer inside a bike or car tyre then inflate it the temperature of the introduced air would rise as a result of the increasing pressure. True/False?
In all the above examples there has been an alteration in temperature that is not a result of heat transfer. It is therefore called Adiabatic. True/False?
ROB
Pressure doesn't affect temperature as far as I know.
Let's go through each statement one by one:
1. Rising air cools as a result of a decrease in barometric pressure with altitude. (Lapse Rate) - True. This statement is true. As air rises and experiences lower atmospheric pressure, it expands and cools due to adiabatic cooling.
2. When an inflatable life jacket is inflated with a compressed air cylinder, the air inside the now inflated life jacket is much colder than it was prior to inflation when it was still compressed inside the cylinder. The air is colder because it is now under less pressure as per the air in question 1. - False. In this case, when the air is released from the cylinder and inflates the life jacket, it undergoes adiabatic expansion, which causes it to cool down. The cooling is not due to a decrease in pressure, but rather due to the expansion process itself.
3. When a Carbon Dioxide fire extinguisher is discharged, the nozzle often freezes. This is as a result of the reduction in pressure. - True. When the carbon dioxide is released from the fire extinguisher, it undergoes adiabatic expansion, which causes its temperature to drop significantly. As a result, moisture in the air can freeze on the nozzle, causing it to freeze.
4. If you were to place a thermometer inside a bike or car tire and then inflate it, the temperature of the introduced air would rise as a result of the increasing pressure. - False. In this case, as you inflate the tire, the pressure inside increases, but there is minimal temperature change. The temperature increase due to compression is typically very small and might not be noticeable.
5. In all the above examples, there has been an alteration in temperature that is not a result of heat transfer. It is therefore called adiabatic. - True. Adiabatic refers to a process in which there is no heat transfer between the system and its surroundings. In all the examples mentioned, the temperature change occurs due to expansion or compression of the air without heat transfer, thus making them adiabatic processes.