A glass vessel measures exactly 10 cm × 10 cm × 10 cm at 0°C. It is filled completely with mercury at this temperature. When the temperature is raised to 10°C, 1.6 cm3 of mercury overflows. Calculate the coefficient of volume expansion of mercury. Coefficient of linear expansion of glass = 6.5 × 10–6 °C–1.
Given:
Volume of a glass vessel: Vg = 10cm x 10cm x 10cm = 1000 cm3.
Volume of mercury in the vessel : VHg = 1000 cm3.( As it is filled completely in the glass vessel)
Temperature at which glass is filled completely with mercury: T1 = 0 °C.
Increased temperature : T2 = 10 ° C.
Change in temperature : Δ T = T2-T1 = 10 ° C.
Volume of mercury overflowed:= 1.6 cm3
Coefficient of linear expansion of glass : αg = 6.5 × 10–6 °C–1.
∴ Coefficient of Volume Expansion of Glass: γg: 3× αg = 3× 6.5× 10-6 °C–1
We need to find Coefficient of volume expansion of mercury : γHg
Formula used:
Formula for Volume expansion is :
Where V’ is the changed Volume of the body at T2 and V is the volume of body at T1.
Now, the Volume of mercury overflown is equal to the difference in changed volumes of mercury and glass respectively.
Numerically:
From the volume expansion formula,
Changed Volume of Mercury: V’Hg = VHg( 1+γHgΔ T)
Changed volume of Glass: V’g = Vg(1 +γg ΔT)
Substituting the values , we get:
Calculate the coefficient of volume expansion of mercury is :
γHg = 1.795× 10-4 ° C-1.
Note: The Steps marked in Bold are important for the numerical.