Does Taking It Apart Change the Mass?

Does Taking It Apart Change the Mass?: Grade 4 Science Worksheet

Do the pieces weigh less than the whole? Many students think a broken chocolate bar or a tower taken apart gets lighter. This sheet shows with simple scales that nothing is lost: the parts always add up to the whole. A block tower reads 80 g on a scale. Students predict what the same four blocks read when they are taken apart, then add parts to find a whole: an orange and its peel, and a chocolate bar broken into pieces.

Key Science Vocabulary

• mass: how much matter (stuff) is in something
• gram (g): a unit used to measure mass
• matter: anything that takes up space and has mass
• conservation of mass: the whole has the same mass as all its parts together
• scale: a tool that measures mass

What Students Do

• Read a short teach box on mass, grams, and why nothing is lost when something is taken apart
• Part A: compare two scales, a block tower at 80 g and the same blocks taken apart, then answer three questions
• Part B: add or take away parts to find a whole (an orange and its peel, a chocolate bar in pieces)
• Answer key with red reason lines that show the adding

Standards

Florida SC.4.P.8.3: Explore the Law of Conservation of Mass by demonstrating that the mass of a whole object is always the same as the sum of the masses of its parts. Builds toward NGSS 5-PS1-2 (total weight of matter is conserved).

Where It Fits in Grades 3 to 8

Earlier grades measure and compare objects. Grade 4 shows that parts add up to the whole. In grade 5 and middle school, the same idea explains why mass stays the same when ice melts, sugar dissolves, or a chemical reaction happens in a closed container.

Teaching Tip

Weigh a stack of linking cubes on a kitchen scale, take it apart, and weigh it again in front of the class. Ask students to predict first. The surprise is the lesson. Prints clearly in black and white and takes 8 to 10 minutes.