Other fluids education resources IV: Science puzzles and fluids lab books

I have been looking around for more demonstrations to use in class and have assembled a list of various books that either directly describe in class activities (or out of class labs) and others that are focused on younger audiences but that can be adapted to demonstrate various fluids phenomena. Some I have described in prior posts but I will aggregate all the books I have come across here. Over the next few months I will be writing up some ideas from all but the first book listed.

H2OH! has an extensive list of in class demonstrations complete with parts lists and descriptions of how to run the activity. The book was assembled by the American Society of Civil Engineers a few years ago so it leans toward civil engineering applications in certain areas. There are a lot of ideas in this book. The only downside is that some of the physical and mathematical explanations are not as rigorous as they could be.

Experiments in Fluid Mechanics (edited by Robert Granger, out of print) contains over 60 experiments that cover fluid properties, hydrostatics, kinematics, dynamics and even acoustics. In general the experiments would be hard to do in class and many of them are now (commercially available) standard teaching laboratory experiments. However, some can be adapted to a class room setting and in all cases the theory and explanations are good.

Professor Povey’s Perplexing Problems: Pre-university Physics and Maths Puzzles with Solutions is mainly focused on physics and math mental problems and apparent paradoxes (such as the Stevin paradox in hydrostatics). The problems are well described though the explanations are sometimes a little wordy. There quite a few hydrostatics problems in the book that I think could really force students to understand the material. They are many of them that easily lend themselves to being demonstrated in class (such as a Galileo balance).

Martin Gardner’s Science Magic: Tricks and Puzzles is mainly focused on using various physical phenomena as ‘magic tricks’. The tricks are simple though there is little in the way of detailed physical explanations. It is not just limited to fluid mechanics so the tricks could be used for a range of undergraduate science classes.

Entertaining Science Experiments with Everyday Objects is another book by Martin Gardner. It is pitched at the same level as their Science Magic book and there is some overlap. Both are worth getting out of the library (or buying, they are not expensive).

Build a Rocket Boat and 18 More Wild Wind Projects (Science Dares You) is aimed at parents of children aged 4-8 so the physical explanations are essentially useless at a college level. However, there are some very simple ideas that illustrate various phenomena. For example, this book had the easiest method for making a Cartesian diver that I have found (see my write up here).

An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.

Video of “Compressibility and incompressibility demonstrated with soda bottles and ketchup”

Here is a video of the “Compressibility and incompressibility demonstrated with soda bottles and ketchup” demonstration. The full video is here.

Video Jan 12, 4 09 29 PM 00_00_02-00_00_11

An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.

Compressibility and incompressibility demonstrated with soda bottles and ketchup

Introduction

I teach in a civil engineering department so we pretty much only deal with incompressible flows. However, this is a really simple demonstration to illustrate the compressibility of gasses and the relative incompressibility of liquids that uses stuff you can pick up at a fast food restaurant and recycling bin. I found it in a number of different books on science experiments for kids.

Equipment

  1. 2 liter soda bottle with cap
  2. a small ketchup (or other condiment) packet that floats (test this before you wedge it in to the bottle).
  3. water

Photo Jan 12, 4 09 06 PM

Demonstration

  1. Stick the ketchup packet into the soda bottle and then fill the bottle with water until there is only a small volume of air below the top of the bottle.
  2. Tightly screw on the cap so that the bottle is sealed. The ketchup packet should be floating.
  3. Squeeze the bottle firmly with your hand and the ketchup packet should sink.
  4. release the bottle and the ketchup packet will float back up to the surface.

Discussion

This is effectively a cheap way to make a Cartesian diver. The demonstration relies on the water being effectively incompressible and the air being compressible. When you squeeze the bottle it is the air pocket at the top of the bottle that is compressed by the change in volume. This increases the pressure in the water but does not compress it so the water density stays the same. However, the ketchup packet has a small air bubble in it which also compresses. This reduces the volume of the bubble enough that the net density of the packet changes from being less than that of water to greater than that of water so it sinks. This process is reversed when you stop squeezing the bottle.

You can also get the packet to sink just by leaving the bottle out in the sun. In this case the water and air both heat up. however, given the finite volume, as the water expands slightly from heating, the air is compressed and the packet sinks.

An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.