$(a)$ $CO_2$ is a gas. Write its two gaseous properties to justify it.
$(b)$ How can we liquefy a gas?
$(c)$ Solid $CO_2$ is also known as dry ice. Why?
$(d)$ Write the full form of:
$(i)$ $CNG$
$(ii)$ $LPG$

(N/A) Gases have large interparticle spaces and no fixed shape or volume,which justifies that $CO_2$ is a gas.
$(b)$ $A$ gas can be liquefied by increasing the pressure and decreasing the temperature,which brings the particles closer together.
$(c)$ Solid $CO_2$ is called dry ice because it undergoes sublimation,meaning it converts directly from a solid state to a gaseous state without passing through the liquid phase.
$(d) (i)$ $CNG$: Compressed Natural Gas.
$(ii)$ $LPG$: Liquefied Petroleum Gas.