Before to go with tis topic students must know the topic thermal expansion of matter, which is one of the most important topic for thermal properties of matter. To learn the topic **Thermal expansion of matter CLICK HERE-**

After Completing the topic thermal expansion ** **students must solve some important questions of thermal expansion of matter, To get (solve)the question based on this topic** CLICK HERE- **

** Change of density with temperature**

*The density of a substance is defined as its mass per unit volume of a given mass of a substance changes with temperature while its mass remain the same , the density undergoes a change with the temperature .*

Consider a body of mass m . Let v_{1} and ƍ_{1} be its volume and density respectively at temperature t_{1} and v_{1}and ƍ_{2} the corresponding values at t_{2}.

Clearly , mass m= v_{2}ƍ_{2}=v_{1}(1+ƳΔT)ƍ_{2}, where ΔT=t_{2}-t_{1} ,

Thus ƍ_{2} = ƍ_{1}/(1+ƳΔT) = ƍ_{1}(1+ƳΔT)^{-1}. = ƍ_{1}(1-ƳΔT)[ Using Binomial theorem]

i.e. ƍ_{2}= ƍ_{1}(1-ƳΔT) [so we can say the density of the material decreases with the rise in temperature].

*Some numericals for practice based on change of density with temperature are given below .*

1. Coefficient of volume expansion of mercury is 0.18 x 10^{-3}/^{0}C . If the density of mercury at 0^{0}C is 13.6g/cc, then its density at 200^{0}C is (a) 13.11g/cc (b)52.11g/cc (c)16.11g/cc (d) 26.11g/cc.

2. The coefficient of volume expansion of glycerin is 49×10^{-5}/K. The fractional change in density on a 30^{0}C rise in temperature is (a)1.47 x 10^{-2} (b) 1.47 x 10^{-3} (c) 1.47 x 10^{-1} (d) 1.47 x 10^{-4}.