What Makes Ice Melt Faster
What Interaction Of Outside Influence Makes Ice Melt Fastest? A. Explain the significance of the
given
factors
in
your
project
design
plan:
•
Problem
statement
•
Relevance
of
your
testable
question
Problem
Statement:
I have lived in a place that during the winter, ice would form on the streets and sidewalks and
have wondered why things such as salt or sand are used over other methods to help de-ice the
surfaces? Why is salt or sand the most commonly used substances when addressing this issue?
Abstract
If you live in a place that gets cold in the winter, you've probably seen trucks out spreading a
mixture of sand and salt on the streets after a snowfall to help de-ice the road. Have you ever
wondered how this works? This basic chemistry project can give you some clues. Objective
The goal of this project is to determine which added material will make ice melt fastest.
Introduction
To make ice cream with an old-fashioned hand-crank machine, you need ice and rock salt to
make the cream mixture cold enough to freeze. If you live in a cold climate, you've seen the
trucks that salt and sand the streets after a snowfall to prevent ice from building up on the
roads. In both of these instances, salt is acting to lower the freezing point of water. For the ice
cream maker, because the rock salt lowers the freezing point of the ice, the temperature of the
ice/rock salt mixture can go below the normal freezing point of water. This makes it possible to
freeze the ice cream mixture in the inner container of the ice cream machine. For the salt
spread on streets in wintertime, the lowered freezing point means that snow and ice can melt
even when the weather is below the normal freezing point of water. Both the ice cream maker
and road salt are examples of freezing point depression. Salt water is an example of a chemical
solution. In a solution, there is a solvent (the water in this example), and a solute (the salt in
this example). A molecule of the solute will dissolve (go into solution) when the force of
attraction between solute molecule and the solvent molecules is greater than the force of
attraction between the molecules of the solute. Water (H2O) is a good solvent because it is
partially polarized. The hydrogen ends of the water molecule have a partial positive charge, and
the oxygen end of the molecule has a partial negative charge. This is because the oxygen atom
holds on more tightly to the electrons it shares with the hydrogen atoms. The partial charges
make it possible for water molecules to arrange themselves around charged atoms (ions) in
solution, like the sodium (Na+) and chloride (Cl−) ions that dissociate when table salt dissolves
in water. Other substances that dissolve in water also lower the freezing point of the solution.
The amount by which the freezing point is lowered depends only on the number of molecules
dissolved, not on their chemical nature. This is an example of a colligative property. In this
project, you'll investigate different substances to see how they affect the rate at which ice
cubes melt. You'll test substances that dissolve in water (i.e., soluble substances), like salt and
sugar, as well as substances that don't dissolve in water (i.e., insoluble substances), like sand
and pepper. Which substances will speed up the melting of the ice? Terms and Concepts
To do this project, you should do research that enables you to understand the following terms
and
concepts:
•Solution
•Solute
•Solvent
•Colligative
properties
•Freezing
point
depression
•Phases
of
matter
oSolid
oLiquid
oGas
oPlasma
•Phase
transitions
oMelting
oFreezing
oEvaporation
oCondensation
oSublimation
Questions
•Which of the suggested test substances are soluble in water? •Which of the suggested test
substances
are
insoluble
in
water?
Bibliography
•For
more
information
on
colligative
properties,
see:
oEli, Todd & Keith, date unknown. "Colligative Properties," Chemworld, ThinkQuest Library,
Oracle
Education
Foundation
[accessed
September
6,
2007]
http://library.thinkquest.org/C006669/data/Chem/colligative/colligative.html?tqskip1=1.
oNave, C.R., 2006. "Colligative Properties of Solutions," HyperPhysics, Department of Physics
and Astronomy, Georgia State University [accessed September 6, 2007]
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/collig.html. •For
information on
Avogadro's number and molecular weight, see: oLachish, U., 2000. "Avogadro's Number,
Atomic
and
Molecular
Weight,"
[accessed
September
6,
2007]
http://urila.tripod.com/mole.htm. oFurtsch, T.A., date unknown. "Avogadro's Number,"
Tennessee Technological University [accessed July 22, 2010] http://iweb.tntech.edu/chem281tf/avogadro.htm.
Materials
and
Equipment
To do this experiment you will need the following materials and equipment: •Ice cubes
•Identical
plates
or
saucers
•Timer
•Electronic
kitchen
balance
(accurate
to
0.1
g)
•Measuring
cup
•Suggested
materials
to
test
for
ice-melting
ability
oTable
salt
oSugar
oSand
oPepper
Experimental
Procedure
1.Do your background research so that you are knowledgeable about the terms, concepts, and
questions, above. 2.You'll need a clean plate and several ice cubes for each of the substances to
be tested. 3.Use the balance to measure the initial mass of the ice cube. For more information
on how to properly use a balance see Chemistry Lab Techniques. 4.Note the starting time, then
carefully sprinkle one teaspoon of the substance to be tested over the ice cube. 5.After a fixed
amount of time (say, 10 minutes), pour off the melted water into a measuring cup, and use the
balance to measure the mass. Subtract the mass of the empty cup, and you'll have the mass of
the melted water. Wait the same amount of time for each test. 6.Measure the remaining mass
of
the
ice
cube.
7.Repeat
three
times
for
each
substance
to
be
tested.
8.Use the same procedure to measure the melting rate for ice cubes with nothing added. 9.For
each
test,
calculate
the
percentage
of
the
ice
cube
that
melted:
[mass
of
10.For
each
[remaining
melt
test,
mass
water]/[initial
calculate
of
ice
the
mass
of
percentage
of
cube]/[initial
mass
ice
the
of
cube]
ice
ice
cube
cube]
×
100
remaining:
×
100
11.For each substance you tested, calculate the average amount of melted water produced (as
a percentage of initial mass), and the average remaining ice cube mass (as a percentage of
initial mass). 12.Did any substances speed up melting of the ice (compared to melting rate of
plain
ice
cubes
with
nothing
added)?
Variations
•Does the melting rate depend on the amount of solute added? Design an experiment to find
out. •Try your experiment in the refrigerator to simulate colder weather. Alternatively, if the
outside temperature is wintry, take your experiment outdoors! Be sure to monitor the
temperature regularly throughout your experiment. •For a related, more advanced experiment
on freezing point depression, see the Science Buddies project Chemistry of Ice-Cream Making:
Lowering the Freezing Point of Water •Do you think salt would melt ice in your freezer? Why or
why not? Try it and find out.