Question

Once ice forms on a lake in winter, the water underneath the ice remains about 4°C, even if the air temperature just above the ice is far below freezing. What property of water helps keep the water below the ice from freezing? a When covalent bonds form between the water molecules in ice, they give off heat. b Each water molecule stores heat in its covalent bonds during the summer and releases it slowly over the winter. c The unstable hydrogen bonds between the water molecules break and push the molecules around, which keeps the water from freezing. d The hydrogen bonds that form in the ice create a lattice structure, and the resulting extra space enables the ice to act as insulation.

Answer 1

A substance floats if it is less dense, or has less mass per unit volume, than other components in a mixture. For example, if you toss a handful of rocks into a bucket of water, the rocks, which are dense compared to the water, will sink. The water, which is less dense than the rocks, will float. Basically, the rocks push the water out of the way or displace it. For an object to be able to float, it has to displace a weight of fluid equal to its own weight.

Water reaches its maximum density at 4 C (40 F). As it cools further and freezes into ice, it actually becomes less dense. On the other hand, most substances are most dense in their solid (frozen) state than in their liquid state. Water is different because of hydrogen bonding.