The purpose is to observe that suspensions are cloudy and contain solid floating parts that can be seen.
Things Required:
Scissors
Cardboard box
2 clear drinking glasses
1 teaspoonful of flour
Torch
Directions:
Turn the cardboard box upside down. Use the point of a pencil to make a small hole in the end of the box. The height of the hole should be one-half the height of the glass being used. Cut a one-inch square viewing hole in the front of the box. The hole must be about three inches from the comer of the box and as high as the small round hole on the side. Fill the glasses three-quarters full with water. Add 1 teaspoonful of flour to one of the glasses with water and stir. Place the glass containing water and flour under the box. Position the glass so that it may be in front of the viewing hole. Hold the torch near the small hole. Observe the effect that the liquid has on the light rays. Put the glass containing only water under the box. Shine the light through the hole and observe the effect that water has on the light rays.
This Is What Happens:
The mixture of flour and water looked cloudy. The tiny particles of flour could be seen floating in the water. The glass of water had no effect on the light rays; they passed through the water unchanged.
Science Behind It:
Flour and water form a suspension. A suspension has tiny particles floating in the liquid. The particles stay suspended until gravity pulls them down. The suspended particles stop some of the light rays. Light hits the bits of flour flooting in the water and is reflected. Tor reflect means to bounce back. There is nothing in the water to reflect the light. Reflection of light by suspended particles is called the Tyndall Effect, named after the British scientist, John Tyndall.
