Grade Level
PreK, K, 1, 2, 3, and 4
Difficulty
Easy
Duration
1 hour
Subjects
Accounting
Algebra
Art
Craft
Design & technology
Engineering
Fun
Mathematics
STEAM
Summer Camp

Directly compare two objects with a measurable attribute in common, to see which object has “more of”/”less of” the attribute, and describe the difference. For example, directly compare the heights of two children and describe one child as taller/shorter.

Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l).1 Add, subtract, multiply, or divide to solve onestep word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem.2

Organize, represent, and interpret data with up to three categories; ask and answer questions about the total number of data points, how many in each category, and how many more or less are in one category than in another.
Vocab
Balance, Weight, Calibrate
Author
Glowforge
Licensing
Lesson for Download
Overview
In this lesson, students will:
 Children learn to compare object sizes from a very young age. It’s a useful skill in identifying the largest piece of cake or biggest pile of candy. As adults, we measure weight to determine how much a package costs to mail, if a truck can safely cross a small bridge or whether we may need to buy new clothing in a larger size. A balance scale is an objective way to compare the weight of two different objects directly. This tutorial describes how to build a working balance scale and ways in which students may use it to explore the concepts of balance, weight and size.
Objective
THE OBJECTIVE
 Learn what it means for objects to have different weights
 Understand the concept of balance and what it means for an object to be balanced
 Understand how a balance scale indicates differences in weight between two objects
 Explore the relationship between size and weight of objects made from the same material
 Compare the weights of objects made from different materials
 Use small objects as a unit of measure to find the weight of larger objects
Supplies
 Proofgrade Medium Draftboard
 Proofgrade Medium Acrylic – any color
 2 or 3 medium size paper clips
 Assortment of small items to weigh on the scale
 Wire cutter
 Needle nose or pointed nose pliers
DESIGN FILES:
 BalanceScale.svg
 Washers.svg
 CalibrationWeights.svg
 BalanceWeights.svg
Design Files
Description
Lesson Outline:
 Build a working balance scale
 Explore how a balance scale compares the weight of two objects
 Estimate objects’ weights and test estimates with the scale
 Compare objects of varying sizes to observe how size and weight are related
Lesson Instructions
Step 1: Setup
This activity requires a sheet of Proofgrade Medium Draftboard, a small amount of Proofgrade Medium Acrylic, a paper clip, wire snippers and pointednose pliers to construct the balance scale. While the scale is easy to use, an adult will need to supervise the construction – particularly when cutting and bending the paper clip. Additional weights, scaled in multiples of a fixed base unit may be cut from any uniform sheet material, such as draftboard or acrylic.
Step 2: Introduction to Weight and Balance
Ask students if they know what weight is. What does it mean for objects to be heavy or light? If they are given two objects, how can they tell which is the heavier of the two? Is the bigger of two objects always heavier than the smaller one? How do we measure the weight of objects in our everyday lives? Ask the students if they know what “balance” means and if they can name examples of things that are balanced. For example, when they attempt to balance themselves on one foot, they are trying to stay upright. If they’ve ever played on a seesaw in a playground, they may have noticed that it is much easier to operate when the people on either side are about the same weight. What happens when a seesaw is not very well balanced – i.e. when the weights on both sides are unequal? If you feel like introducing more advanced concepts, ask the students whether it makes a difference where the riders sit on a seesaw. If an adult wanted to play on a seesaw with a child, where should the adult sit to make it pivot more easily?
Step 3: Ideate:
Ask the students to think of methods they could use to determine which of two objects is heavier without using an electric scale. Do the methods they come up with work well with very small objects (e.g. pennies) and very large objects (e.g. trucks), or are different techniques required to compare weights of small and large objects? In this lesson, students will build and use a balance scale to directly compare the weight of different objects to each other. A balance scale has a long, straight arm (balance arm) which can pivot about its center. If two objects are placed at opposite ends of the arm, equidistant from the pivot, the balance arm will tip, lowering the heavier object and raising the lighter one.
Step 4: Create
Meet Glowforge
The magical 3D laser printer that made this lesson possible. Learn more!