The density of an object is defined as its mass per unit volume. To change the density of an object, you can either change its mass or its volume.

To change the mass of an object, you can:

* Add or remove material from the object.

* Change the temperature of the object. (When an object is heated, its atoms move faster and take up more space, causing the object to expand and its density to decrease. Conversely, when an object is cooled, its atoms move slower and take up less space, causing the object to contract and its density to increase.)

To change the volume of an object, you can:

* Change the shape of the object.

* Compress or expand the object. (When an object is compressed, its volume decreases and its density increases. Conversely, when an object is expanded, its volume increases and its density decreases.)

By changing the mass or volume of an object, you can change its density.