Surface tension is the force that pulls the surface of a liquid together, creating a barrier between the liquid and the air above it. The molecules on the surface of a liquid are more strongly attracted to each other than they are to the air, so they form a thin, elastic membrane that resists tearing.

The strength of surface tension depends on the properties of the liquid. Liquids with high surface tension, such as water, can support more weight than liquids with low surface tension, such as soda. This is because the molecules in a high-surface-tension liquid are more tightly packed, which creates a stronger barrier against the force of gravity.

The density of a liquid also affects its surface tension. Liquids with high density, such as water, have higher surface tension than liquids with low density, such as soda. This is because the molecules in a high-density liquid are more closely packed, which creates a stronger barrier against the force of gravity.

In the case of the paperclip, the surface tension of the water is strong enough to support its weight, even though the paperclip is denser than the water. This is because the paperclip is only a small object, so its weight is not enough to overcome the force of surface tension. In the case of the soda, the surface tension of the soda is not strong enough to support the weight of the paperclip, so the paperclip sinks.