Any object that has a higher temperature than
the ice will begin to melt it. How fast this
happens will depend on what that object is made
of, like metal or plastic.
To better understand this, let's define heat and
temperature. Materials can store energy in the
movement of their atoms, and we call this thermal
kind of energy heat. Atoms move faster in hotter
materials than in colder materials. This energy
can be transferred from hotter atoms to colder
atoms when they bump into each other. Materials
that are at the same temperature will not transfer
heat between them. But, this does not mean that
they contain the same amount of thermal energy.
Consider two pieces of silver that weight 1g and
5g each. They can both be at room temperature but
5g piece has five times the thermal energy because
it has five times the number of atoms.
The amount of heat a material can store (the
capacity) depends on its structure. Generally,
materials that are organized and made of the same
type of atoms (like metals) don't need much
thermal energy to raise their temperature.
Aluminum is a good example - it heats up in your
oven and cools very quickly once you take it out.
Water, on the other hand, doesn't change
temperature easily so you need a lot more heat to
bring water to the same temperature as aluminum.
Materials also take different amounts of time to
transfer their heat (called thermal
Generally, things that store a lot of heat (high
heat capacity) transfer it slowly (low thermal
conductivity) and vice versa.
Imagine that you have an ice cube at 0°C, right at
its melting temperature. Any material at 0°C won't
transfer heat to the ice so it won't melt. But,
any object at any higher temperature (no matter
what it's made of) will transfer some energy to
the ice until they are both at the same
temperature. This will happen no matter how small
the temperature difference.
Let's do some math.How much ice could one
silver at room temperature (25°C ) melt? (I'm
going to assume that there's a lot more ice than
silver such that the temperature of the ice, water
and silver all end up at 0°C at equilibrium.) The
amount of heat energy transferred to the ice is
equal to the amount of silver, the heat capacity
of silver and the temperature difference. Thus,
the silver transfers
( 1g x 0.240 J/g x 25°C ) = 6
joules of heat to the ice.
Since it takes 333.5 J
to melt a gram of ice, only 0.018 g of ice is
That's not much but it is enough to make
the area where the silver touches the ice slick
with water. Now let's do the same math with
plastic. While there are many types of plastic,
most have high heat capacities (~1.67 J/g). Thus,
1 g of plastic at room temperature will melt 0.125
g of ice - nearly seven times as much!
But, if that's the case,why doesn't ice slide on
plastic in the same way that it does on silver?
The key is in thermal conductivity, not heat
capacity. Heat transfers much more quickly from
the silver than from the plastic so the ice melts
much faster. (Less of it melts overall.) Silver
has the highest thermal conductivity of any pure
metal (at 406 W/mK). Check out this table of
If you want to melt ice faster than on silver, you
need a material that is even more organized such
as diamond, conducts heat more than twice as fast
Click Here to return to the search form.