From: Roy Mayeda (roy_mayeda@isd743.k12.mn.us)
Date: Wed Dec 04 2002 - 07:52:35 PST
Date: 04 Dec 2002 09:52:35 -0600 Message-ID: <974356705roy_mayeda@isd743.k12.mn.us> From: Roy Mayeda <roy_mayeda@isd743.k12.mn.us> Subject: Re: pinhole compounds ... pure substances? (Concrete, please?)
Gary,
It's okay -- lots of the rest of us are "non-chemists" too. I get reminded of this almost daily when I teach AP Chem! (I'm officially a biologist, and I still have problems in that area!) Chocolate milk is a mixture -- heterogeneous mixture (has regions larger than molecules that are different in composition from each other). Kids know this one because they shake it up to resuspend the chocolate before drinking it. Water is a pure substance. No matter where you go within it, the particles (molecules) are the same. Scotch is a mixture -- homogeneous mixture (materials are mixed but in chunks not much bigger than molecules, making it hard to identify any different regions unless you're the size of a molecule). It's mostly water and ethanol. Really good scotch is still a mixture. (True, it's usually not blended, but they start out as mixtures.) Concrete would be another heterogeneous mixture. As one of my HS German teachers always said, "Clear as mud, but it covers the ground."
Roy Mayeda
Sauk Centre HS
Sauk Centre, MN
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