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The students will use math expressions and equations to discover that the sum of an objects parts is equal to the whole and that in a chemical reaction or physical change matter is neither created nor destroyed.
For each team of 3‐5 students:
To an adult, the concept that the weight of an objects parts is always equal to the weight of the whole object, and that during a chemical reaction matter is not destroyed, seems the only reasonable way it could be, but to an eleven‐year‐old child this fact is not always that clear cut. Many fifth grade students need a variety of hands‐on experiences before they truly begin to understand and generalize this concept. To facilitate these experiences, students must gain a working knowledge of metric units used to measure weight. This knowledge can only be gained through multiple opportunities to make estimates and use scales and balances to weigh and compare objects.
This lesson uses a whole/part math model drawing strategy to help students understand the relationships between the parts and wholes, reactants, and products in physical and chemical changes. The lesson begins by having students weigh a set of items like a box of crayons and then write algebraic expressions to solve for the weight of the box and one crayon. Next, students weigh an object like a piece of chalk, then break it, write an expression, and solve for the weight of one of the pieces. Finally, students compare the weight of the reactants and the products in a chemical reaction.
Invitation to Learn:
Light a Candle:
Dr. Art's Ball:
Tell the story of Dr. Art's Ball from Dr. Art's Guide to Science pages 52‐57; see Resources) and discuss the differences between a chemical reaction and physical change at a molecular level.
Before class, blow up:
4 red balloons
4 white balloons
1 black balloon
Parts of the Big Apple:
Chalk It Up:
Lesson and Activity Time Schedule:
Activity Connected to Lesson:
Additional Activities With Scales:
Have students bring in items that are made of parts, such as puzzles, small toys, or objects made of Legos. Students can weigh the items, take them apart and determine their weight.