October 2010
3rd Grade: Unit- Weight Watching
Description:
Students will be given an experiment to conduct in groups of four, in which they will use
the balance for larger measurements in grams and kilograms.
Goals/Objectives:
1. Students will improve their skills in estimating the mass of objects
2. Students will gain more experience using the balance to measure mass.
3. Students will understand the need for the larger unit of measure, the kilogram
Materials:
Balances
Cups
Mass sets
Small zip bags
Medium zip bag
Gravel
Apple or orange
Pencils
Marking pen
Vocabulary:
Kilogram – 1000g, or the mass of 1 liter of water
Procedure:
The class will review the metric units for measuring mass (grams) and will also review
the parts of, and how to use the balance.
Each of the four groups will choose several objects to measure the mass of, using the
balance and the mass set. Each student will fill out the page in their science notebook
called “How Heavy Is It?” by listing the name of the object, their estimate of its mass, the
actual measured mass of the object, and finally, the difference.
The students will then attempt to measure the mass of the apple or orange, but they will
soon realize that they do not have enough mass pieces to balance the fruit. They will be
asked for ideas on how to solve the problem.
The groups will be challenged to create their own 100g mass pieces, using gravel and the
small zip-top bags. They will use the mass sets to measure out 100g of gravel (50g at a
time) and will seal the 100g of gravel in a zip-top bag. The students will then label the
bag as a 100g mass piece, using the marking pen. Each group will be making two of these
gravel mass pieces. They will use the gravel mass and the mass sets to come up with an
accurate measurement of the apple or orange. While they work on this, the student intern
will create additional 100g gravel mass pieces in order to bring the total of classroom
gravel pieces to ten.
The class will reconvene and the student intern will explain to the class that the gram is
useful for weighing small objects, but for large objects like a person or a car, a larger unit
is needed. The unit, the kilogram (kg) will be introduced as the equivalent to 1000g. All
ten of the 100g gravel mass pieces will be collected from the class, and they will be
placed into the medium-size zip bag to create a 1kg piece. The students will pass around
the 1kg piece to understand the heft of a kilogram.
Students will then look around the classroom for objects they think may be equal to a
kilogram. As a class, they will observe the measurement of these objects in the balance
together in the front of the room.
The students will return their equipment to the materials station. The class will then come
together for the last 5-10 minutes, and wrap by discussing what they learned from this
lesson.
In the event that the class should finish the activity early, they will have the
corresponding science story from the FOSS kit read to them until the conclusion of the
class.
Conclusion:
Through participation in this activity, the students will learn the concepts associated with
measuring objects of mass greater than 100g. They will also be introduced to the
kilogram, and will understand the importance of a metric unit of mass for larger objects.