Science Buddies: "Ask an Expert"

For my science fair project, I am doing the variation "test the gas-collecting apparatuses" of the experiment "Can you change the rate of a chemical reaction by changing the particle size of the reactants?". First, I need to write a reasearch paper on the topic, and I need good research sites to do that, but I am having trouble finding them. The science buddies experiment describes 2 kinds of gas collecting devices, but I am trying to figure out how to build another similar device and then work out how to compare the 3 devices. Does anyone know about sites where there is information about gas-collecting devices that collect gas from water, and/or know about the topic themselves?

Thank you very much!

Hi,

Assuming the experiment you are referring to is the one in this link:

https://www.sciencebuddies.org/science- ... k&from=TSW

The two methods of gas collection discussed are the two standard laboratory methods used to collect gases over water. Of the two methods the one using the inverted graduated cylinder filled with water in a water trough is the preferred one. The major variation I have seen of this method is to use a titration burrette in place of the graduated cylinder, although if you are not trying to measure the collected gas volume accurately people will use test tubes or bottles in place of the graduated cylinder. If you are trying to get an accurate measure of how much gas has been collected you need to use a collection vessel with volume markings (ie a graduated cylinder or burrette) and ensure that the pressure inside the collection vessel is at a known constant value. This is because the volume of a gas changes with changes in pressure (the ideal gas law: PV=nRT, p = pressure,V=Volume, n = number of moles of gas, R=ideal gas constant, T=absolute temperature). The usual way to do this is to make the water level inside the collection vessel the same as the water level outside the collection vessel, which makes the gas pressure in the collection vessel the same as the room air pressure.

I hope this helps. Good luck with the project.

Best regards,

Barrett L Tomlinson