Most people do not realize that many substances they use in the kitchen and the bathroom are not simple liquids or solids. Everyone is familiar with three states of matter: solids, liquids, and gases. However, creams, shampoo, toothpaste, and ketchup all have properties of both liquids and solids. This paper describes demonstrations and laboratory exercises1 that show intriguing properties of squishy substances, defined as materials that are not unambiguously solid, liquid, or gas. Unlike some areas of physics, the concepts behind squishy materials are understandable even by beginning students. Squishy physics can be used to show physics questions arising from everyday life and to convey the excitement of current research.
Topics
Educational aids
REFERENCES
1.
Additional materials and associated movies can be viewed at EPAPS Document No. E-PHTEAH-44-013605 (ftp://ftp.aip.org/epaps/phys_teach/E-PHTEAH-44-013605/). For more information on EPAPS, see http://www.aip.org/pubservs/epaps.html.
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A.
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For example: a change of temperature of water from 30°C to 20°C results in about 20% drop in viscosity. To learn more visit http://www.hbcpnetbase.com (CRC Handbook of Chemistry and Physics, 84th Edition).
4.
Light mineral oil, 1 L — around $40 (Fisher Scientific No. MX1561-1).
5.
Glycerol (99+%), 1 L — about $24 (Fisher Scientific No. 31549-K2).
6.
Acrylic beads, Grove Tech Sales, Albany, GA; 229- 883- 7279. 50-pound bag — $18. See also http://www.rodeco.com for a wide selection of glass spheres.
7.
Regular sand can be purchased from Home Depot —$10 a bag.
8.
Xanthan gum, 100 grams — $17 (Fisher Scientific No. 96002180).
9.
Bentonite, 500 grams — $11 (Fisher Scientific No. A15795-3 6).
10.
H. M.
Jaeger
, S. R.
Nagel
, and R. P.
Behringer
, “The physics of granular materials
,” Phys. Today
49
, 32
(April 1996
);J.
Kakalios
, “Resource letter GP-1: Granular physics or nonlinear dynamics in a sandbox
,” Am. J. Phys.
73
, 8
(Jan. 2005
).11.
Richard A.L. Jones, Soft Condensed Matter (Oxford University Press, 2002).
12.
F.A. Morrison, “What is rheology anyway?” online on The Industrial Physicist at http://www.aip.org/tip/INPHFA/vol-10/iss-2/p29.html.
13.
14.
V. F.
Weisskopf
, “The privilege of being a physicist
,” Phys. Today
56
, 48
(Feb. 2003
).
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© 2006 American Association of Physics Teachers.
2006
American Association of Physics Teachers
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