Re: Why can water start to freexe at 32 degrees F and why can an icecube start-

    Hi Carista,

      That's a good question...What you stumbled on is tricky in a way because 
it can be looked at from two different perspectives.  

      If you have a chunk of ice and you apply some constant heat to it while 
watching the temperature, you would see the ice start to heat up, then  reach 
32 degrees Fahrenheit, at which point the ice would start to melt.  If you pay 
real close attention to the temperature you would see that when you reach this 
point, the temperature would stop at 32 F until all the ice melts and becomes 
liquid water.  Once all the ice has melted you would then see the temperature 
start to go up again (this is the water starting to heat up...).  This is 
because the heat being put into the ice, initially goes towards heating it up, 
then when it gets to 32 F all of the heat energy goes towards changing the 
state of the ice from a solid into a liquid because the molecules are re-
arranging themselves.  Once this is completed, the heat then starts to just go 
towards heating the water.  
     Now let's look at it another way, such as having some liquid water and 
then freezing it by putting it in a freezer, for instance.  Just like above, 
only backwards, we would see the temperature of the water drop until the water 
reached 32 F, then the temperature would stay constant as the water changed 
into its solid form, ice.  Once this change in its state was complete, then the 
temperature would start to drop again.
     The confusing thing is that it looks like two things can happen when we 
reach this point and we say to ourselves: "that's impossible; you can't have 
two things happening at the same time!".  And you'd be right to say that, only, 
in this situation there is only one thing which is happening at this 
temperature.  At 32 F water changes from one state into another, but you still 
might say:"which way does it change, and what if I stop right at 32 F?".
     At 32 F there is a balance or an equilibrium bewteen the liquid water and 
the solid water (ice).  The balance is broken if we either start to heat it or 
take heat away from it (cooling), which then causes it to either completely 
melt or completely solidify.  You've probably heard this temperature called the 
"melting point" or the "freezing point".  By the way we just explained, this is 
known as the temperature at which water undergoes a "phase change".  This means 
a point at which a substance experiences a change in it's physical 
characteristics from one form to another.
     So to summarize, water can undergo this change in its state by one process 
which happens in two opposite directions (forwards or backwards) depending on 
what you are doing to it (heating or cooling...).  It can sometimes be a little 
confusing to try to visualize because our eyes tell us that two different 
things are happening.  

     I hope this helped to clarify...
 
     If you still have questions, just write us back and we'll help if we can.