Question

Substances that assume the shape of their container, but do not have a definite size are called?

Answer 1

Any substance with that description would be called a "gas". A gas takes the shape AND the size of whatever container you put it in.

Answer 2

Liquid

Explanation:

When you place a liquid in a container, liquids take that shape, whether it is a bottle or a can or a packet etc , This is because the molecules of the liquid are free to move, compared to solids and so assume the shape of the container in which the liquid is poured.. Liquids have volume that is measured in units like liters , cubic meters, milli liters etc.

Any amount of liquid can be poured into a container of any shape. That is, if there is a 100 liter container, just 10 liters of liquid can be poured in it. That is the meaning of they do not have a definite size.