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Teacher Materials Snow Globe Lab Reference: Haugh, Thomas. 2001. Snow Globe Science. The Science Teacher 69(3): 36-39.

Teacher Materials Snow Globe Lab

Disclaimer:

The idea for this lab originally came from an article in The Science Teacher by
Thomas Haugh (see reference at the bottom of each page in this lab). Though I
let him know ahead of time that this lab would be posted on my site, he hasnt
read over this incarnation of the lab and cannot be held responsible for any
mistakes or problems you may encounter. He has, however, graciously allowed
me to post his email address for anybody who has questions or problems with
the lab. He can be contacted at Tom_Haugh@gwinnett.k12.ga.us

.

Another disclaimer:

As with all laboratory activities, there are inherent dangers involved. If for any
reason you feel uncomfortable doing this lab in your classroom, please dont do
this lab! By doing this lab, you indicate that you take full responsibility for your
actions and any problems or damage that result. Remember to have your
students wear goggles at all times!

About this lab:

The point of this lab is to show students how solubility is important in the real
world. Using their knowledge of solubility and like dissolves like, your students
will make working snow globes out of some common household solvents and
solutes. There are many correct combinations of solvents and solutes which
may be used, to varying degrees of success.

Before doing this lab, you should make sure your students understand what like
dissolves like truly means, and how to find the relative polarities of various
compounds. Briefly, polar covalent compounds tend to dissolve other polar
covalent compounds (and some ionic compounds), while nonpolar covale nt
compounds generally dissolve neither. While working chemists are usually
interested in finding solvents that will make various solutes dissolve, the snow
globe lab has the opposite goal. Ideally, their solute should not be dissolved by
the solvent they choose, because the goal is to make small particles of solute fall
like flakes in the solvent.

There are a few ways of doing this. The simplest is for students to pick a
nonpolar solvent (such as mineral oil or vegetable oil) and a polar solute such as
Epsom salts or sodium chloride. A more complex way for students to do this is to
have them pick a solute that dissolves well in a solvent and make a saturated
solution such that the undissolved solute can move freely around the globe. This
method, while seemingly foolproof, is much harder to make work than simply
picking insoluble solutes unfortunately, solutes dissolve very quickly at first,
then more slowly as the solution reaches saturation. Students making a Reference: Haugh, Thomas. 2001. Snow Globe Science. The Science Teacher 69(3): 36-39.

sucrose/water solution may find that it takes them a very long time (and a very
large quantity of sucrose) to make a saturated solution.

Grading this lab is determined by how nice their snow globe looks. Emphasize to
your students that theres more to real world chemistry than just making things
happen usually, we want to make them happen in a way that other people find
interesting or beautiful. After all, what good would a deodorant be if it smells like
rancid ham? Who would want to buy purple sunblock, even if it did guarantee
that the wearer could avoid skin cancer?

Overall, students seem to really enjoy this lab. Though it can be a bit of a mess
(as well discuss later), the kids have something fun to show their parents (which
makes both kids and parents feel good) as well as tangible evidence for future
students that chemistry is a lot of fun. After all, isnt that part of our job, too?

Equipment:
One small baby food jar for each student. Students will bring these in for
themselves if you give them a few days warning. One small oil and waterproof item for each snow globe. Have the
students bring an ine xpensive item from home. Hot glue gun. Package of 24 glue sticks. 32 oz. of vegetable oil. 10-16 oz. bottles of mineral oil. (Note: As mineral oil is used as a
laxative, be prepared to have store clerks look at you a little funny when
you buy this much at once. You may want to explain that youre a science
teacher and not a weirdo.) 32 small vials with lids. 2 lb box of kosher salt. 2 lb box of table salt. 2 lb carton of Epsom salts (magnesium sulfate heptahydrate). 5 lb bag of table sugar (sucrose) 1 lb bottle of talcum powder. 1 lb of sand. 1 lb box of sodium bicarbonate. 1 bottle of concentrated ammonia (for cleaning up).

The quantity of supplies required for this lab is less expensive than you might
imagine. The students will provide the baby food jars, and if your science budget
cant afford the full cost of this lab, many can be persuaded to bring in some of
the other supplies with extra credit incentives. Reference: Haugh, Thomas. 2001. Snow Globe Science. The Science Teacher 69(3): 36-39.

Safety issues:

As with all labs, students should wear goggles at all times. There isnt really
anything in this lab that can cause eye damage, but its a good habit for students
to get into. Additionally, it might be a good idea to have lab aprons on hand, as
students will spill mineral and vegetable oil on the countertop and lean into it,
staining their shirts.

A hot glue gun will be used in this lab to hold the plastic items inside the snow
globes and to seal the top of each snow globe. Though many students may
already be familiar with the operation of a glue gun, its best to keep a close eye
on the action, as hot glue can cause bur ns if it sticks to bare skin. Despite the
danger of burns DO NOT let students wear rubber gloves during this lab, as
melted rubber will stick to the skin just as badly as hot glue. If you are worried
about liability issues, have the students bring their snow globes to you for gluing.

The other main safety hazard in this lab involves the slipperiness of mineral and
vegetable oils. If either are spilled on the floor, it will become slippery enough
that students may trip and fall. If youve got a small class, you can probably
clean up the spills as quickly as they appear for larger classes, simply place
paper towels over the spills to make them less dangerous.

Room destruction factor:

It varies. If you arent careful, you may find that there are giant puddles of oil all
over your classroom. These puddles may take a considerable amount of time to
clean. On the other hand, if you stay on your students to clean up their messes
as they make them, this shouldnt really be a problem. For good measure,
devote the last five minutes of class solely to clean up.

How the lab works:

Students will be provided with the lab sheet and told to make a snow globe. Its
pretty much a free form activity, where the students will devise their own
procedure and materials for the lab. Before making the snow globes, encourage
your students to test their solvent/solute combinations in small vials to minimize
waste.

Combinations Ive seen work best in this lab include mineral oil/magnesium
sulfate, mineral oil/kosher salt, and vegetable oil/magnesium sulfate. Sand tends
to make sandstorm globes rather than snow globes, and both talcum powder
and sodium bicarbonate simply make a very milky liquid thats hard to see.
Water makes a lousy solvent, as it dissolves most of the solutes.

Chances are excellent that both you and your students will have a really good
time with this lab. Its fun to see your students making the snow globes, and
even more fun when they make one that theyre really proud of. I recommend Reference: Haugh, Thomas. 2001. Snow Globe Science. The Science Teacher 69(3): 36-39.

that before you do this lab with your class you make one that you can show your
students after they are completed.

What can go wrong:
Students sometimes pick items made of clear plastic to go into the snow
globes. Normally, this wouldnt be a problem, but the index of refraction of
clear plastic is close enough to that of mineral oil that its hard to see.
Before doing this lab, discourage students from bringing in transparent
items. Students cant get the tops to stop leaking. To fix, just keep dumping the
glue until all of the holes are sealed. Students get big clumps of snow that wont break up. This sometimes
ha