| MadSci Network: Physics |
Hi Michelle! Viscosity is a cool subject, though it can be difficult to convey to people without resorting to long descriptions. I'll leave the describing to you, and offer you these suggestions for demonstrations: The maple syrup race: Maple syrup is much more viscous than water, and you can show this by pouring some water and some maple syrup down an inclined plane. The marble race: Take a couple of graduated cylinders, and pour into one some water (or baby oil) and the other karo (corn) syrup. Drop a marble into each. The difference in speeds is slight, but noticable. If you have access to longer cylinders, even better, as this demonstration is aided by long falls. Temperature dependent viscosity: Take some melted candle wax and pour it into a jar. Note it's low viscosity and it's other flow properties while hot. Let cool slightly and pour it into another jar. Note the decrease in temperature causes an increase in viscosity. Repeat until it hardens. The volcano: Volcanoes act the way they do because of the different viscosities of the magma within them. Hawaiian volcanoes have less viscous lava than volcanoes in Washington State, and because of this they act differently. Hawaiian volcanoes erupt often, giving off large amounts of material that slowly flows out and forms a broad shield. Washington State volcanoes erupt infrequently, with great force, throwing huge amounts of material into the air and surrounding areas. This is because the material is so viscous, it allows tremendous pressures to build up before eruption, increasing the force of the eruption. Here's how to demonstrate this: Take two squeeze bottles (the squeezier the better -- I first did this with a full and empty toothpaste tube!) and fill one bottle with water, and the other with a viscous susbtance like Karo Syrup. Squeeze gently on the water bottle and observe how the water flows out with very little force. Squeeze the Karo Syrup bottle and note how difficult it is to make it flow upward. Now squeeze super hard and it will come out of the tube -- it required much more force to do it! The reason I like to do this with toothpaste tubes is simple: for my viscous substance, I use toothpaste! The other I fill with water (Note that this takes a little time and patience). Squeezing the water one causes an easy flow, a low viscosity action. Squeezing the toothpaste with equal force causes no flow, so you have to squeeze MUCH harder to get an eruption! I hope this helps your project! Take Care and Be Safe, Steve E. Williams Rock Star and Science Demonstrator Pacific Science Center, Seattle, Washington, USA
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