Properties of WaterDensity, Surface Tension

Imagine walking down the street on a rainy day. You see a puddle, and on the top you notice a thin layer of rainbow couloured liquid. Why is that?

Density

This is because of a liquids Density. The oil on top of the rain water is less dense.

Wood floats on water because it is less dense Boats float better on salty seawater because it is more dense thanfreshwater. Usually thicker liquids are the mostDense.

Density

What will happen if a piece of paper is thrown into some water, will it float or sink?

What will happen if the same piece of paper is crumpled and than thrown into the water, will it float or sink?

Why do you think that is?

Floating and Sinking

The paper will float the first time, and sink the second. Why?

Density is the Volume of the object, divided by the Mass.

The flat paper has MORE volume than mass, thus it will float.

The crumpled paper has LESS volume, thus it will sink.

Floating and Sinking

Try this to understand Density a bit better

http://phet.colorado.edu/sims/density-and-buoyancy/density_en.html

Density Activity

This photo is a perfect example of Surface Tension.

Small drops of water are usuallyRound because the water moleculesPull together. The result is a “skin”Formed over the small ball. Surface Tension is onlyStrong enough to work on smallBalls of water, or filled glasses.

Surface Tension

It is due to this skin that water bugs can walk on water.

Examples of Surface Tension

Understand surface tension with a video! https://www.youtube.com/watch?

v=e1RVOc0VZ30

Surface Tension Video