You can conduct an activity to teach students the important difference between mass and weight, both of which relate to gravity. First, explain that mass is a measure of the amount of matter in an object and that weight is a measure of gravitational pull. Then, have students calculate mass based on weight. Use the formula W = mg, where W = weight, m = mass and g = the acceleration of gravity. Explain that on earth, the acceleration of gravity is 9.8 meters per squared second. Guide students to calculate their mass using this formula, as well as the mass of other objects around the classroom, such a dictionary or ream of paper.
You can use a class activity to teach students that mass is unchanging, but weight depends on the gravitational force between objects. For this activity, show students a chart that depicts the differences in gravitational pull throughout space. For instance, show students that gravitational pull on the moon is approximately one/sixth the pull on earth, which means that a person weighing 120 lbs. on earth would weigh 20 lbs. on the moon. Challenge students to calculate their weight in different parts of outer space.
Some activities are designed to visually demonstrates weight's relationship to gravity. Have students collect different objects from around the classroom, using objects of diverse weights, textures and forms. For instance, use a feather, piece of paper, foam ball, book, pencil and penny. Have students stand on top of a chair and drop the objects, two at a time, to see which object touches the ground first. Ask students to record the results of tests and then discuss the results. Challenge students to consider what factors, in addition to weight, implicate the rate at which an object falls. For instance, explain that the texture of a feather may cause resistance.
Some activities show that gravity can be counteracted by other forces. For this activity, show that free fall -- which is the way objects fall when influenced by gravity alone -- is affected by forces such as wind. Drop objects in front of a fan to see how wind interferes with free fall. Change the settings on the fan to show how velocity, or the amount of force counteracting gravity, impacts the extend to which gravity is counteracted.