Date: Tue, 7 Oct 1997 08:26:09 -0700
Message-Id: <v02140b01b05f94bf89cb@[136.152.2.65]>
To: pinhole@exploratorium.edu
From: suzanna@seismo.berkeley.edu (suzanna loper)
Subject: Re: basic chemistry questions from new teacher (sublimation)
I'll let the Chemistry teachers tackle those first questions, but
regarding question number four, no! Matter can go directly from a solid to
a gas ... this is called "sublimation" as opposed to melting (it probably
talks about it somewhere in your chemistry textbook) and a wonderful
example of this is dry ice (my kids sometimes call it "hot ice"), which is
solid CO2, and sublimates into gaseous CO2 without going through a liquid
... which is what makes it so nice for keeping things cold without getting
them all wet. If you get a chunk of dry ice you can do some nice
activities or demos with it ... put a small piece into a test tube with a
balloon sealed over the top and as it sublimates the balloon inflates; do
the same thing with a piece tied inside a rubber glove. Drop it into water
and it makes lots of "steam"; add dishsoap to the water and it makes a big
mess. Drop it into water with an acid-base indicator and it will change
colors as the CO2 makes it more acidic. Stick a coin or other piece of
metal into a chunk of dry ice and it starts vibrating (I think this has to
do with the metal contracting from the cold and then expanding again, but
I'm not sure). In Oakland you can get dry ice at the AM/PM gas station on
West Grand; I'm not sure if there's a place closer to El Cerrito.
Someone correct me if I'm wrong, but when the [normal] ice cubes in
your freezer "shrink" over time, I think this also due to a very slow
process of sublimation.
Good luck! Have a great year.
Suzy Loper
physics/physical science teacher
Skyline H.S./Oakland
>Monday, October 6, 1997
>Hello Pinholers,
>
> I am a new Science Teacher and a newcomer to this discussion
>group. I found out some weeks into the semester that I will be teaching
>Life Science as well as Earth Science. I have a number of rather basic
>questions that I realize I could probably find answers to elsewhere but
>I'm hoping for quick answers here. I apologize if these questions are
>too basic.
>
>1) What are these substances and what exactly are they used for. I've
>seen them asked for in Labs or merely found them on my chemical shelf and
>am curious:
> - Bromothymol Blue
> - Methylene Blue - (I know it's a stain for looking at cells
> under a microscope, but how does it work)
> - Limewater Solution
> - liquid blueing
> -phenol red
> - Bristol's Media
>
>2) I'm assuming HCL is hydrochloric acid, (right?). If I have a 3 Normal
>solution and want to get to 1 Normal solution to I dilute it 1 part to 3
>parts water? What exactly does 1 Normal mean?
>
>3) I have a 1% solution of Bromothymol Blue on my shelf. Does that mean
>1 gram of powder for 100 mls of water?
>
>4) On a more general note, do all elements have to transition through a
>liquid phase on their way to becoming a gas from a solid, (a student's
>question)
>
>Thanks in advance,
>
> Jory Gessow
> Middle School Science Teacher
> Tehiyah Day School, El Cerrito
> gessow@well.com
Suzy Loper
suzanna@seismo.berkeley.edu
suzyl@socrates.berkeley.edu (not yet functioning)