Mass, Volume, and Density

Mass, Volume, and Density

Middle School

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Learning Objectives

Key Vocabulary

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Mass

The amount of matter an object contains. It is measured in grams or kilograms using a balance.

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Volume

The total quantity of three-dimensional space that an object or substance occupies, measured in mL or cm³.

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Density

This property of matter reflects how closely packed its particles are. It's calculated as mass per unit volume.

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Meniscus

The curved upper surface of a liquid in a container. It should be read at the bottom for accuracy.

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Water Displacement

A method for determining the volume of an irregular object by measuring how much fluid it displaces.

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What Are Mass and Volume?

Mass

• ​Mass is the measure of the amount of matter that is present in an object.

• ​​The standard units for measuring mass are grams (g) or kilograms (kg).

• ​A triple beam balance is a scientific tool used to precisely measure an object's mass.

Volume

• ​Volume is the total amount of three-dimensional space an object or substance occupies.

• ​​Volume is measured in cubic centimeters (cm³) for solids and in milliliters (mL) for liquids.

• ​It is important to remember that 1 mL of a liquid is equal to 1 cm³.

Multiple Choice

Which of the following statements correctly describes the difference between mass and volume?

• Mass is measured in milliliters (mL), and volume is measured in grams (g).

• Mass is the space an object occupies, and volume is the amount of matter it has.

• Mass is the amount of matter in an object, and volume is the space it occupies.

• Mass and volume are two different words for the same property of matter.

How to Measure Volume

• Measure a liquid's volume by pouring it into a graduated cylinder.

• For a regular solid, multiply its length, width, and height.

• Find an irregular solid's volume using the water displacement method.

Multiple Choice

A student needs to find the volume of a small, irregularly shaped rock. What is the correct method to use?

• Measure its length, width, and height with a ruler and multiply them.

• Pour the rock into an empty graduated cylinder and read the volume marking.

• Use a triple beam balance to find its mass, which is equal to its volume.

• Place it in a graduated cylinder with water and subtract the initial water volume from the final volume.

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What Is Density?

• Density is how much mass is packed into a certain given volume.

• An object with tightly packed particles has a very high density.

• An object with particles spread far apart has a low density.

• A bowling ball is denser than a volleyball of the same size.

Multiple Choice

Based on the concept of density, why does a bowling ball feel heavier than a volleyball of the same size?

• The air inside the volleyball is denser than the plastic of the bowling ball.

• The particles inside the bowling ball are more tightly packed.

• The bowling ball has a larger volume.

• The volleyball contains more massive particles.

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Calculating Density, Mass, and Volume

Multiple Choice

An object has a mass of 150 g and a volume of 50 cm³. What is its density?

• 0.33 g/cm³

• 100 g/cm³

• 3 g/cm³

• 7500 g/cm³

Comparing Densities: Sink or Float?

• An object's density determines if it sinks or floats in water.

• Objects that are denser than water will sink.

• Objects that are less dense than water will float.

Multiple Choice

An object has a density of 0.85 g/cm³. What will happen when it is placed in a container of pure water (density 1.0 g/mL)?

• It will sink to the bottom.

• It will dissolve in the water.

• It will float on the surface.

• It will change its density to match the water.

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Common Misconceptions About Density

Misconception	Correction
Heavy objects sink and light objects float.	Floating and sinking depend on an object's density, not its weight.
Mass and volume are the same thing.	Mass is the amount of matter. Volume is the space an object occupies.
The final water level is an object's volume.	You must subtract the starting water volume from the final volume.
Bigger objects are always denser.	Density is mass divided by volume. A large blimp has low density.

Multiple Choice

A block of aluminum has a volume of 15.0 cm³ and a mass of 40.5 g.
What is its density?

• 1.5 g/cm³

• 2.7 g/cm³

• 3.5 g/cm³

• 4.0 g/cm³

Multiple Choice

Object A has a mass of 100g and a volume of 50 cm³. Object B has a mass of 120g and a volume of 40 cm³. Which object is denser and why?

• Object A is denser because it has a lower mass.

• Object A is denser because it has a larger volume.

• They have the same density because their mass and volume are proportional.

• Object B is denser because it packs more mass into a smaller volume.

Multiple Choice

A student has a rock with a mass of 75 g and a volume of 30 cm³. The student places it in a beaker of liquid that has a density of 2.8 g/mL. What will happen to the rock and why?

• The rock will float because its density is 0.4 g/cm³, which is greater than the liquid.

• The rock will sink because its density is 0.4 g/cm³, which is less than the liquid.

• The rock will sink because its density is 2.5 g/cm³, which is less than the liquid.

• The rock will float because its density is 2.5 g/cm³, which is less than the liquid.

Multiple Choice

A scientist discovers a new material. A 2 cm³ sample has a mass of 10g. To save money on shipping, the scientist wants to know if a large 10,000 cm³ block of this material will float on water (density 1.0 g/mL). What is the correct prediction and reasoning?

• It will sink because it is heavy, with a mass of 50,000g.

• It will float because large objects always float.

• It will sink because its density is 5 g/cm³, which is greater than water.

• It will float because its density is 0.2 g/cm³, which is less than water.

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Summary

Poll

On a scale of 1-4, how confident are you about calculating mass, volume, and density?

• 1

• 2

• 3

• 4