Science Connections
Chapter 2 Section 2












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1.5 class periods

2-2 Mass and Weight

The purpose of this section is to introduce students to the concepts of mass and weight, two important general properties of matter. Mass is the amount of matter in an object and is measured in grams (g) and kilograms (kg). An object has weight because its mass is attracted by the gravitational force of the Earth. The force of attraction between objects is called gravity.

The themes that can be focused on in this section are patterns of change, systems and interactions, and stability.

Patterns of change: Stress that unless matter is added or taken away from an object, the mass of that object remains constant. The weight of the object, however, can change as the object is moved farther away from the center of the Earth. As such, gravitational forces between objects diminish when the distance between objects increases.

Systems and interactions: All objects interact through gravitational forces between them. The strength of the gravitational force is dependent on the mass of the objects and the distance between them.

Stability: The mass of an object remains constant, or stable, unless matter is added to or taken away from the object. Weight, however, is dependent on both mass and location and is not constant.

Performance Objectives 2-2

  1. Explain why the mass of an object is constant whereas weight can change.

  2. Discuss the relationship between mass and inertia.

  3. Define gravity.

  4. Compare mass and weight.

Science Terms 2-2

Mass, p.42

Inertia, p.43

Weight, p.45

Gravity, p.46

  • What instrument is used to measure mass?

  • In what units is mass measured?

  • What does it mean if one object has a mass of 5 grams and another object has a mass of 20 grams?

  • What does a seat belt do for a passenger when a car stops suddenly?

  • Why would the passenger move forward without the restraining force of the belt?

  • What would stop a passenger not wearing a seat belt?

  • Why do we not feel the pull of gravity of Jupiter, when its mass is so great?

  • What is mass? What is weight?

  • How are mass and inertia related?

  • The moon is smaller than the Earth. Where would you weight less? Where would you have less matter?