A single glass of water can be an excellent teaching tool. Add a couple of extra items and you can be actively demonstrating a number of different scientific principles with your homeschool students over a glass of water.
Surface Tension
To physically demonstrate the surface tension on the top of water, fill a glass almost completely to the top. Now add a few coins from the side. Make sure that you do not add them from the center as that will eliminate the surface tension. Now keep adding coins and count the number it takes to break through the bulging surface tension on top of the glass.
Diffusion
It is easy to show the process of two liquids mixing if they are of two different colors. Add water to a glass and create a mixture of colored water in a second glass. Now use a dropper to collect the colored water and before you add it to the glass of plain water give it a stir with a spoon. You will see how the drops of colored water travel through the glass before they diffuse completely with the plain water. The homeschool student may also try to add drops of colored water without disturbing the plain water in the glass. The process will be slower but easily observed.
Refraction and Reflection
Place a glass of water on a table’s edge and place a sheet of white paper at a lower level. This will allow the sun’s rays to shine through the water in the glass and split up into the colors of a rainbow on the plain white sheet below through the process of refraction and reflection. The process is similar to the actual rainbows created in the sky due to water droplets in clouds.
Change in Sound Frequency
Line up four glasses and fill them each with varying levels of water. Now use a metal spoon to strike the glass. Each glass will have a distinctly different sound due to the vibrations of the water molecules within the glass. This is a principle also used in a musical instrument known as the Jal Tarang.