What is the Difference between Mass and Weight?
Problem Solving Skills in Gifted Integrated Science and Math Classes
Mar 2, 2009
Students need to experience the difference between mass and weight in science to understand the dissimilarity. Understanding this concept will aid them in determining the difference when classifying the properties of matter in objects. This difference between mass and weight idea is also important for making connections with other science concepts, for example that mass (volume and shape) never changes, although weight changes according to gravitational pull.
Mass is important because of two factors affecting how objects move due to inertia (Newton’s 2nd Law of Motion) and gravity (weight). Newton’s 2nd Law of Motion reflects that a force is needed to move an object and how fast it moves is directly tied to its mass. This is why heavy objects with a lot of mass are hard to move; on the other hand once the heavy object is moving, its mass is difficult to stop.
Misconceptions about Mass and Weight
Typical misconceptions that students have about mass and weight include the ideas that mass and weight are equal at all times, mass and weight are the same thing, and mass is determined by weighing an object.
Often students have difficulty with these misconceptions because the mass and weight of an object are considered a constant on earth. This constant is not the same when transferred to space, or to other planets and moons in our solar system.
Another basis for these misconceptions is that the metric system (which is the standard for science measurements) uses mass, while the U.S. measurement system uses weight.
Investigating Mass and Weight Differences
This investigation is designed for gifted and talented students in grades 4-5 to use their critical thinking skills as they solve problems. Students use problem solving and science process skills (both basic and integrated) as they complete this investigation.
Materials (per group)
- One spring scale
- One balance scale
- Three 100 g masses
Procedures
- Students place one 100 g mass on the spring scale.
- Students place the other two 100 g masses on the balance scale and balance the scale.
Student Questions
Part 1
- If both scales were taken to the moon, what would the spring scale read?
- Would the balance scale remain balanced? Why or why not?
- If both scales were taken to Jupiter, what would the spring scale read?
- Would the balance scale remain balanced? Why or why not?
- If both scales were taken to Venus, what would the spring scale read?
- Would the balance scale remain balanced? Why or why not?
- If both scales were taken to Space, what would the spring scale read?
- Would the balance scale remain balanced? Why or why not?
- If both scales were taken to Antarctica, what would the spring scale read?
- Would the balance scale remain balanced? Why or why not?
- What does this demonstrate?
Twenty questions to ask students in science projects provides additional for ideas for developing additional questions.
Part 2
The weight of an object on earth depends on the force of gravity between the object and earth. Using this equation F = G(M * m/r squared) – where “F” is the force of attraction, “M” is the mass of the earth, “m” is the mass of the object, “r” is the distance between the center of mass of the two objects, and G is for Gravitational Constant.
- What does this equation show?
- What will cause the force of attraction to increase or decrease?
- If either the mass of earth or the object increases, what happens to the force of gravity?
- If r = 1 (standard for earth), then what would happen if r = 2? Equals 5? Equals 10? Equals .167? Equals 2.34?
Making Connections
Understanding scientific inquiry-based investigation applications is important for providing students with the opportunity to use critical thinking skills to solve problems as they make connections with other science concepts, for example density, volume, shape, gravity, gravitational force is inversely proportional to distance, etc. Problem solving strategies in integrated science and math involve the use of formal operational skills, proportional reasoning, and logical-deductive thinking.
