Final answer:
Water molecules are farthest apart on average in the gas state, known as water vapor. This is due to the low density of gases compared to liquids and solids, with the molecules widely spaced as they have overcome intermolecular attractions.
Step-by-step explanation:
The question asks to select the state of water in which the water molecules are farthest apart on average. The answer is c. Gas (water vapor). In the gaseous state, the molecules of water vapor are much farther apart compared to the liquid and solid states due to the lower density of the gas state. Liquids have molecules that are closer together but not fixed in place, allowing them to flow, while solids have molecules in fixed positions creating a definite shape.
Looking at the density aspect, the average distance between molecules increases as we go from solid to liquid and then to gas. This is because heating water to convert it from solid (ice) to liquid (water) and then to gas (steam) provides enough energy for the molecules to overcome the intermolecular forces that hold them together in the solid and liquid states, resulting in an expansion and increased spacing between the molecules in the gas phase.