How many moles PVC pipe

This activity does a few things:

1) is a hands-on activity

2) provides an opportunity to use the Vernier LabQuest and pressure sensor

3) is sort of fun

4) setup is easy, but data is pretty good

Setup

- 3/4" PVC pipe ~ 4 foot per experiment

- during COVID, we had only 4 groups (one person operated the LabQuest, one person "blew") collect data, others just processes the data.

- LabQuest + pressure sensor

- one-hole stopper with luer connector to pressure sensor

- tape measure for measuring length/diameter (volume) and PVC pipe cutter (optional, but a fun tool).

Experiment

- with pressure sensor connected via a flexible tube to the end of the PVC pipe, one student operates the LabQuest and the other

person who blow sharply into the PVC pipe (quick blow, not extended or sustained - trying to hit a max pressure). This was repeated until the pressure exerted was relatively constant.

- data was collected using in plot mode and the highest pressure could be read off the LabQuest.

- after first calculations are complete, if time available do second run with PVC pipe of 1/2 length.

Calculations

- how much air did you blow into the pipe?

- need to calculate the volume of the PVC pipe...length and diameter.

Expected Data

- students exert pressures between 7 and 16 kPa inside the PVC pipe...independent of the length.

- using PV=nRT --> n=(PV)/(RT)...using 29 g/mol as an average molecular weight of air (can students calculate this?), 12 kPa ~ 0.001 moles ~ 35 mg of air.

- try not to treat this as a competition...higher is not better (??? not sure if this is true)