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Sunday, October 13, 2013

The Law of Conservation of Mass

Mass- the amount of matter in an object
Conserve- to save or preserve 

Science discussions sure can get interesting in 4th grade! 
As one example, our classes have recently been having pretty deep discussions about the Law of Conservation of Mass,  a scientific law established in 1789 by French Chemist Antoine Lavoisier. This law states that the mass of a whole object is always the same as the sum of the masses of its parts. In other words, part + part = whole (sum).

To explore this idea, students participated in an inquiry lab using a block of clay and a balance scale. First, they measured and recorded the mass (in grams) of a block of clay. Next, they cut the clay block into two parts and estimate the mass of each part. After making their estimates, each part was massed and these measurements were recorded. 
The discussions were centered around whether or not the mass of the two smaller parts added up to equal the mass of the original whole before it was cut. Students correctly determined that the only way it made sense for the overall mass of the clay blocks to "CHANGE" would be if clay was either added or taken away. 

Students, leave a comment which provides another example of mass conservation. You might leave an example like this one: 
A flat piece of aluminum foil is crumpled up into a ball. The shape changes, but the "mass" does not change because material was not added or taken away. 


  1. A robot broken up into pieces. Even though the shape is different, the mass stays the same because no pieces have been added and no pieces have been taken away.
    -Joe M.

  2. Even if you change the shape of the object it DOES NOT change the objects mass [stuff] that it has.All you would be doing is changing the shape of the object.But if you did want to change the mass you would have to take some of the mass away like ripping a paper into smaller peices. love your hard working scientist lexie


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