Chapter 9

In chemistry class you have probably witnessed the phenomenon of "bumping" in a test tube (the explosive boiling that blows the contents of the tube all over the ceiling). Yet you have never seen this happen in a kitchen pot. Explain why not.

Water boils on a large flat plate at \(1 \mathrm{~atm}\). Calculate \(q_{\max }\) if the plate is operated on the surface of the moon (at \(\frac{1}{6}\) of \(g\) earth-normal). What would \(q_{\max }\) be in a space vehicle experiencing \(10^{-4}\) of \(g_{\text {earth-normal? }}\) ?

(a) Suppose that you have pits of roughly \(0.002 \mathrm{~mm}\) diameter in a metallic heater surface. At about what temperature might you expect water to boil on that surface if the pressure is \(20 \mathrm{~atm}\). (b) Measurements have shown that water at atmospheric pressure can be superheated about \(200^{\circ} \mathrm{C}\) above its normal boiling point. Roughly how large an embryonic bubble would be needed to trigger nucleation in water in such a state.