Question

Answer the following questions:
(1) Why are liquids and gases categorised as fluids? [1 mark]
(2) Three closed containers, each having a volume of 1 m${}^3$, contain 1 m${}^3$ of substances X, Y, and Z. X is a solid, Y is a liquid, and Z is a gas. X, Y, and Z are then carefully transferred without spillage to another three closed containers having a volume of 5 m${}^3$ each. Compute the new volumes of X, Y, and Z. [3 marks]

Answer 1

(1) Liquids and gases are called fluids due to their ability to flow. The fluidity in both the cases is due to the fact that their molecules are free to move around. This is because, in these states, the interparticle space between molecules are large enough to let them tumble over one another. [1 mark]
(2) Solids and liquids have a definite volume, which means that substance X (solid) and Y (liquid) have fixed volumes and their volumes do not depend on the volume of container. So, when X and Y are transferred to the new containers, their volumes will be same as their initial volumes. Thus, the new volumes of $X=Y=1$ $m^3$. [2 marks]
Gases do not have a definite volume and occupy all the available space in the container. So, the volume of the gas depends on the volume of the container. When Z (gas) is transferred to the new container, it expands and takes up all the volume of the new container. So, volume of Z increases from 1 $m^3$ to 5 $m^3$. Therefore, the new volume of $Z=5$ $m^3$. [1 mark]