Re: Which will food coloring mix into faster, hot, trepid water or cold water

Your question is very interesting and a little complicated.  
Let's start by defining the types of colors that we use on a daily basis.  
There are two types of colors used in industrial applications, Natural and 
Artificial.  Natural colors are found in things like beets (red), lemon 
zest (yellow), and blueberries (blue).  These colors are more complex and 
harder to define.  Let's just talk about artificial (man-made) colors  
here.  There are only 6 artificial colors certified safe for Food, Drugs, 
and Cosmetics (FD&C), they are:
FD&C Blue   #1:  This is sky blue.
FD&C Blue   #2:  This is the blue used in blue jeans.
FD&C Red    #3:  This is bright red.
FD&C Red   #40:  This is blood red.
FD&C Yellow #5:  This is lemon yellow.
FD&C Yellow #6:  This is actually orange, but called yellow.
All of these colors, except for FD&C Yellow #5, have slightly better 
solubilty at warmer temperatures.  Scientists usually measure temperature 
in degrees Celsius (C), so I would recommend a Celsius Thermometer with 0-
100 C scale (you could probably borrow one from school), room temperature 
is about 25 C, hot water is about 60 C, and water freezes at 0 C.  Your 
experimental theory is correct (which is called, LeChatelier's Principle: 
equilibrium of a solution process shifts in the direction that absorbs 
heat.)  So by adding more heat to a solution processs that absorbs heat 
you will uncrease the speed that the color is dissolved in the water.  The 
FC&C Yellow #5 is the best of the colors to demonstrate this principle.  
The FD&C Yellow #5 has a much better solubility at room temperature than 
at cold temperatures.  If you put some Yellow #5 into a beaker of warm 
water it will dissolve very quickly, but if you put the beaker into an ice 
bath, the color will begin to precipitate (fall out) out of solution.  
This is because the #5 Yellow has to absorb more heat to go into 
solution.  This is called an Endothermic process.  The solution process 
for most gasses is the opposite, which is called an Exothermic process.  
This means that solubility decreases with increasing temperature.  An 
example of this process is that soda will become flat as it is allowed to 
warm to room temperature.  The dissloved Carbon Dioxide (bubbles) escapes 
from solution.