Do students understand the basic characteristics of a “good” weight line?

For evidence, look at responses to the Dear Darwin Concept Cartoon. Use these criteria as you interpret students’ critiques of the 4 weight lines:

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• Are the distances between neighboring tick marks equal in length?
• Do equal lengths represent equal differences in weight?
• Does the weight line start at 0?
• Is there a place on this weight line for each of the dog biscuits?

As a next step you might provide a small set of objects and their weights. Ask students to help you create a “good” weight line.