are atoms of the same element with different masses because the number of neutrons in those atoms is different.

water and alcohols have similar properties because water molecules contain hydroxyl groups that can form hydrogen bonds with other water molecules and with alcohol molecules, and likewise alcohol molecules can form hydrogen bonds with other alcohol molecules as well as with water.

metric time was an attempt to create a standard unit of time based off of 10, but it never took off an is not included in the metric system (si)