Simple Conservation of Mass Activity

Lee Walkerby: Lee Walker

When we are doing a Partnership for Science Adventure on phases of matter we like having this conservation of mass experience in the bag of tricks. It can be done in minutes and is extremely reliable. All you need is the simplest (and least expensive) OHAUS classroom balance from Educational Innovations, the Ice Melting Block set from Educational Innovations, a pair of wire cutters and some paper clips, (just in case you need to whip up some mass bits of less than a gram) and a nicely formed ice cube. We like to use the aluminum blocks and O-rings from two of the Ice Melting Block sets just to simplify the balancing and have found that having more than one set of the blocks is good for the original activity anyway.

Here we go…….

Step 1)

Place the materials  on a level surface with the balance set.

OHAUS School Balance Conservation of Mass

Materials for Conservation of Mass Activity:

A)  Set of brass weights

B)  2 or three paper clips and wire snips

C)  Classroom balance

D)  Aluminum Ice Melting Blocks and rubber O-rings

E)  Ice cube on a dish (actually, a Styrofoam meat tray is better than a saucer as it is very non-conductive, and the ice cube retains its temperature even better than on a ceramic surface.

Step 2)

Place the ice cube in the tray on the right, add necessary weights to achieve balance,


As the ice cube melts and water collects inside of the O-ring the balance is retained!

OHAUS School Balance Conservation of Mass

OHAUS School Balance Conservation of Mass

OHAUS School Balance Conservation of Mass

Step 3)

Note that the ice cube is completely melted… (Actually long before the time indicated by the watch)… and the balance is right on the mark! No gain or loss. Only the form of matter has changed. All of the matter is still accounted for.

The Ice Melting Blocks allow this to be done without having to be concerned with evaporation OR loss of student interest. Lots of good data can be gathered, the phenomena discussed and conclusions drawn.

There you have another case where the Walker brothers rely on Educational Innovations and Jim Housley’s wonderful inventions!


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