Water

This video shows three of the five properties of water: surface tension, adhesion and cohesion.

 

When the plastic card is gently placed on the surface of the water in the bowl, it floats. This is due to surface tension. As the water molecules form hydrogen bonds between them, they stick together and effectively create a surface “skin” which can support light objects. Since hydrogen bonds are easily broken, surface tension can be easily penetrated. In this case, the card breaks through the surface tension and sinks to the bottom when it is dropped into the water.

 

The video also demonstrates adhesion and cohesion. Several water droplets can be seen adhering to the side of the bowl, despite gravity. Water molecules stick to objects and surfaces, often defying gravity and other forces. When the bowl is tilted and the water level gets close to the drops, they cohere together into one body of water. Water molecules attract other water molecules because they are polar and subject to electromagnetic forces. Cohesion causes water molecules to seek and attract other water molecules, if they are in close enough proximity.

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