The density of a liquid of coefficient of cubical expansion γ is ρ at 0∘C. When the liquid is heated to a temperature T, the change in density will be
−ργT(1+γT)
The density of the liquid at temperature T is given by ρ′=ρ1+γT
Now, change in density is ρ′−ρ=ρ1+γT−ρ
=−γρT1+γT
Hence, the correct choice is (a).