An annealed bobby pin is heated, then cooled quickly; this process is called hardening. The hardened bobby pin is brittle.
The tempering process, which involves heating a hardened bobby pin then cooling slowly, transforms the brittle metal into springy metal.
A metal bobby pin is heated until red hot, then allowed to cool slowly; this process is called annealing. The annealed bobby pin is very flexible.
As the temperature of the benzene increases, the meniscus flattens, then disappears as the system reaches the point where liquid and vapor are in equilibrium.
The liquefaction of carbon dioxide is shown. In Part 1, dry ice is placed in a strong plastic tube and a pressure gauge is attached.