Mass

• Define mass and weight, and learn the key differences between them.

• Explain why mass is constant, but weight changes depending on the location.

• Describe how to use a triple beam balance to measure an object's mass.

Key Vocabulary

Mass

Mass is the amount of matter in an object and is measured in grams or kilograms.

Weight

Weight measures the force of gravity on an object and changes based on the location’s gravitational pull.

Scalar Quantity

A quantity, like mass, that has only a magnitude or size but does not have a direction.

Vector Quantity

A quantity, such as weight, that possesses both magnitude and a specific direction associated with it.

Triple Beam Balance

A lab instrument used to find an object's mass by balancing it against known masses.

Mass vs. Weight

• An object's mass is the amount of matter in it and is constant.

• Weight is the force of gravity on an object, so it can change.

• An object has the same mass everywhere, but its weight can change.

Measuring Mass with a Triple Beam Balance

• A triple beam balance is a tool used to accurately measure mass.

• ​You slide riders on three beams until the pointer balances at zero.

• The beams measure mass in 100s, 10s, and single grams with decimals.

• Add all three readings to find the object's total mass (e.g. 225.4 g).

• A triple beam balance measures mass (which stays the same everywhere), unlike a spring balance, which measures weight and changes with gravity.

• An object's mass is a constant measure of the matter inside it.

• An object's weight is a force that changes depending on the pull of gravity.

• Mass is a scalar quantity, while weight is a vector quantity.

• A triple beam balance is used to measure the mass of an object.