Will It Hold Water?

This project reinforces the curricular objective of calculating volume for grade 8 students in a simple but very fun way. 

Sometimes it gets so fun that I have to stop the class and read the riot act (they get so excited). 

The kids take one class to design and construct a box that holds 576 milliliters of water. 

In the next class we measure the volume by pouring water into the box. 

Everytime I do this activity the lower performing kids usually do better than the high performers.

Get some stiff card stock like manilla tag, bristol board (or whatever you call it where you live).

Students will need scissors, pencil, math set, eraser, clear tape, duct tape, glue, stapler...

On test day you will need to supply two 500 ml beakers, two 100ml graduated cylinders, a container to dump water into, and some sort of brace for the box to prevent the sides from "bowing out".

My kids have so much fun with this that I need my best classroom management skills.  Remember it's all in fun.  My students probably learn more deeply during these two periods than the entire year.

I tell the students to sketch/design a box that will hold 576 ml of water.

Sometimes I tell the students that I have to check and sign-off on their designs. 

Other times I just let the kids go at it.  Then I watch the smart-alecks try and build a box that measures 1 cm by 1 cm by 576 cm.

But, hey, you're a teacher.  You know when to intercede and when to let genuis take its course.

Previous to this I have taught a unit on geometric construction where the kids have built boxes, pyramids, etc...  However, designing a box is not rocket science so you don't worry if you haven't done geometric construction. In an effort to win this competition some of the kids will become rocket scientists.

So have them layout a box.  Explain that the glue tabs will make the box easier to construct.  If you are really prepared you will have a layout, previously cut out, so that you can model the use of the glue tabs in folding and gluing/taping.

I encourage the kids to use a ruler to make straight, neat folds.

Then glue the tabs.  Some of them clear tape over the glued tabs.  The keeners reinforce their corners with staples. 

I try to encourage them to think ahead to testing day and design a rugged box.

As the kids duct tape the box, make sure they reinforce the edges with strips of tape; this is where the box usually leaks.

Watch for excess duct tape consumption.  Some student put so much tape on their box I suspect it would survive an artillery barrage.

If the students don't finish it in class, assign it for homework.

Those kids who come to class without it next day, when they see the fun their classmates are having, can quickly whip one off and join the end of the competition.  Happens every year.  One year a hastily constructed box won the competition, much to the chagrin of the keeners with engineering-type moms/dads.

(this activity really makes you love the low performers - God Bless 'em)

So it's the next day.  The kids who don't have their box finished are working like mad in the background...  Let them...  this activity can make you a lot of allies. 

I place a plastic container next to my desk to dump the box into once its volume is measured.

I have used old books and bricks to brace the box as it is being filled, preventing it from "bowing out".  What I use now is a woodworking clamp.  Whatever you use, you must be prepared for it to get wet.

I have the first two students fill a 500 ml beaker and a 100 ml graduated cylinder.  If they are not careful to fill them precisely, they soon learn that they have cheated themselves. 

Tell the kids that they can pour or you will pour for them.  Rarely do I get a kid who wants to pour themselves so usually I do it.

Quickly pour the 500 ml beaker into the box.  Then add water from the 100 ml graduated cylinder until it just reaches the top.  If you still don't have enough water, borrow some from the kid who is waiting in the wings.

At this stage the poorly taped boxes begin to leak so I push them off the desk into the plastic container.  This adds a pleasing element of wet, squishy action to the competition that the kids love.

Then I glance at the graduated cylinder.  I announce how much water is left and the kids gleefully calculate and then scream the resulting volume to the kid recording the results on the board.

If I have a really keen class, I put the results on the classroom smartboard, using an excel data sheet, and they have fun manipulating it.

Just a word on scoring:

Announce how much water is left over.  Let the students fill in the rest on the board chart.  If the scorekeeper makes a mistake, the others will soon let them know. 

I tell them that by completing a box, they start with a mark of 100%.  Every milliliter over or under 576 ml earns them one demerit point.  If the design is bad, and they are badly off,  I limit their mark automatically to 50%.

You can play with this system and do what is best for your class.

As the first student finishes, the second student is ready with their beaker and graduated cylinder.  The third student now takes the first's beaker and graduated cylinder and fills them (at the water fountain, bathroom, or from a source in your class).

If your kids are like mine, you will have to stop occasionally to quell the riot.  They get so passionate about this simple activity that it brings a tear to your eye (or makes you pretty grouchy, depending on how many coffees you had before the start of class).

Some students aren't happy with their marks; I give them a chance to improve their score by writing a thoughtful response to the activity.  Deep thinking can go on here.  Students inadvertently learn about things like meniscus, specific gravity, oblate-ness and experimental error.  The odd one will go home and do a total redesign/rebuild.  One student actually taught himself the concept of  cubed roots by trying to design  a cube that held 576 ml. 

In designing the box they also experience factoring in a real way  (what three factors yield a product of 576ml?)

I could go on and on.

But if I can leave you with a last word of wisdumb(sic):

Other than classroom management, try to talk as little as possible during this activity.  Give them the assignment verbally and let them guide their own learning. 

Enjoy!