Final answer:
A coin is able to float on top of water in a glass due to surface tension, which is the cohesive force between water molecules that forms a 'skin' on the surface. The weight of the coin is spread out over a larger area, allowing the surface tension to support its weight and make it float.
Step-by-step explanation:
A coin is able to float on top of water in a glass due to a phenomenon called surface tension. Surface tension is the cohesive force between water molecules that holds them together at the surface, forming a 'skin'.
When a coin is placed on the surface of water, it doesn't break the surface tension because the weight of the coin is spread out over a larger area. This allows the surface tension to support the weight of the coin and make it float.
Surface tension can also be observed with other objects, like sewing needles or paper clips, which are denser than water but can also float on its surface due to surface tension.