Question

which statement helps to explain why ice is less dense than liquid water? (a) water molecules make hydrogen bonds at definite angles. (b) cold molecules move less than warm molecules. (c) hydrogen bonds lengthen in the cold. all of the above. both (a) and (b). part j the open spaces in waters crystal structure make it possible for... (a) aquatic life to exist at the north pole. (b) water to have a low boiling point. (c) life to occur in hot springs.

Explanation:

For the first question, water molecules in ice form hydrogen - bonds at definite angles creating an open - lattice structure which makes ice less dense. Cold molecules moving less is a general property and not the main reason for ice's lower density compared to water, and hydrogen bonds don't lengthen in the cold in a way that explains density. For the second question, the open spaces in water's crystal structure allow ice to float, which is crucial for aquatic life to exist in polar regions like the North Pole as the ice layer insulates the water below. Water's boiling point is related to intermolecular forces in general and not specifically to the open - lattice structure, and life in hot springs is due to other factors like heat - tolerant organisms and chemical composition.

Answer:

First question: A. Water molecules make hydrogen bonds at definite angles.
Second question: A. aquatic life to exist at the North Pole.