In: Physics
A measuring cylinder made of glass has a volume of 200 mL when measured at 20°C. Mercury, also at 20°C, is added to the measuring cylinder until the mercury level reads 197 mL on the measuring cylinder scale. The mercury and glass are then warmed until the mercury level reads 200 mL on the measuring cylinder scale. Taking the coefficients of volume expansion of glass to be 2.0 × 10-5 K-1 and for mercury to be 18 × 10-5 K-1, what is the final temperature?
Note that the coefficient of volume expansion of glass is much
smaller than that of mercury. So, it is a good approximation to
ignore changes in the measuring cylinder and find the final
temperature by considering the expansion of only mercury. With this
approximation we need to find the increase in
temperature
so that the volume of mercury increases from 197 mL to 200 mL.
Change in volume of mercury is
Coefficient of volume expansion is fractional change in the
volume per unit change in the temperature. So,
Therefore
The value of
in
is same as the value of
in Kelvin .
Therefore, final temperature is about 104.6 degree Centigrade.