Ok, I'm going to get a little more technical in explaining what people are seeing in the snow tests.
Point 1: Snow is an insulator, it retards the transfer of heat.
definition:
Insulator:
Any material that keeps energy such as electricity, heat, or cold from easily transferring through is an insulator. Wood, plastic, rubber, and glass are good
insulators.
reference:
http://www.igsoc.org/journal.old/43/143/igs_journal_vol43_issue143_pg26-41.pdf
Journal of Glaciology, Vol. 43, No. 143, 1997
The Thermal Conductivity of Seasonal Snow
MATTHEW STURM,I JON HOLMGREN,I MAX KONIG,2 KIM MORRIS2
1 US Army Cold Regions Research and Engineering Laboratory, Po. Box 35170, F t. Wainwright,
Alaska 99703-0170, USA.
Geophysical Institute, University of ALaska, Fairbanks, ALaska 99775, USA.
The fact that snow is an insulator makes melting it harder than melting ice. More energy is required to melt snow than ice
Support for the above claim:
Thermal conductivity is a measure of the property of materials to conduct or transfer heat. It is measured in watts per meter x degrees Kelvin (
W/(
m·
K)).
Reference:
http://en.wikipedia.org/wiki/List_of_thermal_conductivities
1. Thermal conductivity of ice: 1.6-2.22 (
W/(
m·
K))
2. Thermal conductivity of (dry) snow: 0.05-0.25 (
W/(
m·
K))
The thermal conductivity of ice is greater, at 1.6-2.22 than that of snow, at .05-.25. This means that heat is conducted faster through ice than it is conducted through snow.
Point 2:
The snow can retain water by capillary action.
definition:
http://science.howstuffworks.com/dictionary/physics-terms/capillary-action-info.htm
Capillary Action, or Capillarity, the tendency of liquids to rise or to be depressed in tubes of small diameter. Capillarity is due to the adhesion of the liquid to the sides of the tube, and to the surface tension of the liquid.
Capillary action can be seen when a corner of a paper towel is touched to spilled water. The water soon spreads into other parts of the towel because loose fibers have spaces between them that act as capillary tubes. The drying action of a bath towel is also due to capillarity. Kerosene rises in the wick of a lamp through capillary action. Compact soil has very small, continuous spaces through which water tends to rise by capillary action.
reference:
http://books.google.com/books?id=0VW6Tv0LVWkC&pg=PA107&lpg=PA107&dq=capillary action of snow&source=bl&ots=8UjB_x3H1s&sig=DriZdLD8Imq_vY5LwwABKGB5FLo&hl=en&sa=X&ei=xCPsUqewD-HXygHr1YDIAg&ved=0CD8Q6AEwAw#v=onepage&q=capillary action of snow&f=true
Snow and Glacier Hydrology, Volume 792367677
By P. Singh, Vijay P. Singh page 107
Conclusions:
Snow, being an insulator, does not conduct heat a
s fast as ice does, thus it will not reach melting temperature as quickly when heat is applied as does ice.
Water is known to be retained in snow by capillary action, which will retard even further the time required for a visible portion of water to emerge from snow when heat is applied.
