Ask A Scientist Chemistry Archive

Question:  My 6 year old daughter was looking at a glass of Pepsi with ice.  
She asked me why the center of the ice cube was white and the edges were clear.  
Can someone please answer her question?  Thanks.
frank s horvath

Answer:
Frank,
The center of an ice cube is white because it is full of bubbles
and other defecrts like cracks and boundaries between ice crytsals.
They are found in the center more than at the surfaces because the
the water freezes from the outside in, and at a fairly slow raTe.
This allows the outer ice to solidify with fewer defects than
the later ice.  This is a major problem in casting metals and other
things as well.
Ed