Water is absorbed by some materials.

Water beads up on some material.

Q: Why does water make a sponge expand?

Q: Does squeezing the dropper gently make the water fall more slowly?

Q: Would water bead up more easily (form better domes) on foil that is not wrinkled?

Water forms a dome on a flat surface.

Surface tension makes water form a sphere or a dome.

Soap added to water reduces its surface tension.

Q: Would the surface tension be the same on a dime?

Q: What else could we add to water to change its surface tension?

 Water flows DOWN a slope.

 Bigger domes of water move down a slope faster.

 Water flows faster down a steeper slope.

Q: How does water get clean?

Q: What stopped some of the water drops from flowing down the slopes?

Q: Can we speed up the flow by using another surface, like glass?

 Water expands when heated.

 Water contracts when cooled.