Helium (He) has the lowest melting point of <span>-272.2 °C.</span>
Helium is a light gas. Movement can be predicted by which chamber has the lighter gas(es) and which chamber has the heavier. constant changes can also be a variable. If the gas is constant, then changes are more easily predicted.
A metal rail rusting in damp weather.
273g/25 mL = 10.92 (that's the density)
What has a density of 10.92 grams/mL? I don't know but I bet it's in your notes or on the worksheet.