The purpose of this assessment probe is to elicit students' ideas about weight and mass when a property of an object changes. The probe is especially designed to determine whether students recognize that although weight and mass are different, both the weight and mass of an object stay the same when the object changes shape. Because many students learn that an object's mass is the same on the Earth and the Moon, but its weight differs (the object will weigh less on the Moon than on the Earth), they may apply this rule to contexts other than location, such as change in shape.