Demonstrations for Chapter 5: The Gaseous State

1. Barometer. A mercury barometer is simply constructed from a length of glass tubing, closed at one end and completely filled with mercury and placed, inverted, in a pool of mercury. A standard atmosphere corresponds to 760 mm Hg, 760 torr, 101.3 kilopascals (kPa, 1.013 bar, or 14.7 lb/in2 (psi). Note 1 bar = 105Pa.

 

2. Pressure. The crushing pressure (P=F/A) of the atmosphere can be visually demonstrated by its ability to collapse structures of varying strengths within which the pressure has been reduced.

 

3. Gas Thermometer. A simple thermometric device, used by DaVinci 500 years ago, works on the effect of temperature on the volume of a trapped gas.

 

4. Charles-Gay-Lussac's Law. The general relationship between V and T for a gas can be demonstrated by heating and cooling gas-filled balloons.

 

5. Molar Volume. Recall the molar volume of an ideal gas at STP: 22.414 L.

 

6. Gas Densities. Observe the relative gas densities of several gas-filled balloons.

 

7. Boyle's Law. The glass column has an area of 1 cm2 so the height gives us a direct measure of the volume. There is a stopcock at one end and the other is connected to a leveling device filled with mercury. With this device, we can demonstrate the inverse relationship between pressure and volume which is the basis for Boyle's Law.

 

8. Dalton's Law. The total pressure exerted by a mixture of gases is the sum of the partial pressures of the individual components, as demonstrated by the change in pressure recorded on addition of an additional component to the air trapped in a simple barometer.

 

9. Diffusion. The gas phase reaction of hydrogen chloride and ammonia produces a solid product, ammonium chloride, which appears as a smoke-like display of particles.

The same reaction carried out in a long tube provides a demonstration of the relative velocities of the gases. Where in the tube will the reaction occur relative to the midpoint? . Assuming the tube is a meter in length and that the plugs are saturated and inserted in the ends, simultaneously, at what distance from the ammonia plug will the reaction occur?

 

10. Effusion. Hydrogen effuses through the walls of the porous cup faster, accounting for the pumping of fluid from the flask's spout.