Question

Although steel is denser than water, a steel needle or paper clip placed carefully lengthwise on the surface of still water can be made to float. Explain at a molecular level how this is possible:

Short answer

The bug or paper clips are supported by the layer through hydrogen bonds.

Step-by-step solution

Explanation of molecular level

Since water molecules can form hydrogen bonds therefore these water molecules are attracted strongly to one another and exhibit a relatively large surface area forming a type of layer at its surface.

Hence the layer can support a bug or paper clip if gently placed on water.