A substance whose shape can easily change is called a liquid.

Here's why:

* Liquids take the shape of their container because their particles are able to move around freely. They have a definite volume but no definite shape.

* Solids have a definite shape and volume because their particles are tightly packed and vibrate in place.

* Gases have no definite shape or volume because their particles are far apart and move randomly.

Let me know if you have any other questions!