There is only one known pure substance which, as a liquid, cannot be frozen by cooling alone at 1 atm pressure. Which is it?
a) water (H2O)
b) nitrogen (N2)
c) mercury (Hg)
d) helium (He)
e) hydrogen (H2)
2. Which of the following solid substances can be liquefied simply by increasing the pressure sufficiently?
a) ice (H2O)
b) diamond (C)
c) sulfur (S)
d) dry ice (CO2)
e) graphite (C)