# Density vs. Weight: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on November 23, 2023
Density is the mass per unit volume of a substance, while weight is the force exerted by gravity on an object's mass.

## Key Differences

Density measures how compact the mass of a substance is within a given volume, representing the concentration of matter. Weight, however, is the gravitational force acting on an object's mass, varying with gravity.
The density of an object remains constant regardless of location, as it is a ratio of mass to volume. In contrast, weight changes with the strength of the gravitational field, being different on Earth and the Moon, for example.
While density is a property intrinsic to the material and is expressed in units like grams per cubic centimeter, weight is a force measured in units like pounds or newtons.
High density implies a large amount of mass in a small volume, but it doesn't directly inform about the weight. Conversely, high weight indicates a strong gravitational pull on the mass, not its density.
In scientific and engineering contexts, density is crucial for determining whether substances will float or sink in a fluid, while weight is key in designing structures to withstand gravitational forces.

## Comparison Chart

### Definition

Mass per unit volume
Gravitational force on mass

### Units

Grams per cubic centimeter (g/cm³), kilograms per cubic meter (kg/m³)
Newtons (N), Pounds (lbs)

### Changes with Location

Remains constant
Varies with gravitational strength

### Physical Implication

Indicates how compact a substance is
Measures gravitational force on an object

### Example

Gold has high density
An object weighs less on the Moon than on Earth

## Density and Weight Definitions

#### Density

Mass of a substance per unit volume.
The density of water is 1 g/cm³.

#### Weight

The force exerted by gravity on an object.
The weight of the backpack was too heavy for the child.

#### Density

Degree of compactness of a material.
Lead has a higher density than aluminum.

#### Weight

A measure of the heaviness of an object.
She checked the weight of the package before shipping.

#### Density

Relative heaviness of substances with the same volume.
Metals generally have a higher density than plastics.

#### Weight

The gravitational pull on an object's mass.
Astronauts experience less weight in space.

#### Density

Amount of mass in a given space.
High-density materials are used in bulletproof vests.

#### Weight

The downward force exerted by an object due to gravity.
The bridge’s design must account for the weight of traffic.

#### Density

Concentration of particles in a space.
The density of the gas decreased as it expanded.

#### Weight

A unit for measuring how heavy something is.
The weight of the elephant is over 2 tons.

#### Density

The quality or condition of being dense.

#### Weight

A measure of the heaviness of an object
A contest to guess the weight of a pig.

#### Density

The quantity of something per unit measure, especially per unit length, area, or volume.

#### Weight

The force with which a body is attracted to Earth or another celestial body, equal to the product of the object's mass and the acceleration of gravity.

#### Density

The mass per unit volume of a substance under specified conditions of pressure and temperature.

#### Weight

A unit measure of gravitational force
A table of weights and measures.

## FAQs

#### Is density affected by gravity?

No, density is independent of gravity.

#### What units are used for density?

Common units are g/cm³ or kg/m³.

#### Does high density mean high weight?

Not necessarily, as weight also depends on gravitational force.

#### Why do astronauts feel weightless in space?

Due to the microgravity environment, reducing gravitational pull.

#### Does weight change with location?

Yes, weight varies depending on the gravitational force.

#### Can density be used to identify a substance?

Often yes, as many substances have unique densities.

#### Can weight be zero?

Yes, in a zero-gravity environment, weight can be zero.

#### What affects an object's density?

Density is determined by how closely mass is packed in a volume.

#### Can the density of a substance change?

Yes, with changes in temperature or pressure.

#### Is density a fundamental property of matter?

Yes, it is an intrinsic property of a substance.

#### Does air have density?

Yes, air has a density, though much lower than solids or liquids.

#### Why do ships float despite their weight?

Ships float due to their design, which disperses weight over a large area, reducing overall density.

#### Is weight a vector quantity?

Yes, since weight has magnitude and direction (towards the center of gravity).

#### How is density related to buoyancy?

Objects with lower density than the fluid they are in will float.

#### Can two objects have the same weight but different densities?

Yes, depending on their volume and material.

#### Is density important in material science?

Yes, it's crucial for understanding material properties and applications.

#### Does the density of a liquid change with shape?

No, density is independent of shape.

#### What is the difference between mass and weight?

Mass is the amount of matter in an object, weight is the force exerted by gravity on that mass.

#### How do scales measure weight?

Scales measure the force exerted by an object due to gravity.

#### Can weight be measured in kilograms?

Kilograms measure mass, but it's often used colloquially for weight.