Thinking Scientifically 01

Natural phenomena often require an explanation. Based on how sodium chloride dissociates in water (see page 28) and Figure 2.12, explain why the oceans don’t freeze.

Figure 2.12 Ice is less dense than water. a. Water is more dense at 4°C than at 0°C. Most substances contract when they solidify, but water expands when it freezes, because in ice, water molecules form a lattice in which the hydrogen bonds are farther apart than in liquid water. b. This property of water allows ice to flow, providing habitats for some aquatic species and protecting other species that live beneath the ice.