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Module 4: Liquid Characteristics - Density and Specific Gravity - Answers
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#1
- Using Table 2, find the percent increase in the density of water
for the following sets of temperatures:
- -5°C compared to 200°C
- 15°C compared to 75°C (Usual range used in air pollution
control)
- -5°C compared to 200°C
- Answer: i. 15.82%
- Solution:
-
- Answer: ii. 2.49%
- Solution:
-
There is a significant difference (16%) in the densities of water as it heats from -5°C to 200°C (Part i). But, such wide temperature fluctuations for liquids are normally not encountered in air pollution control. Part ii, with a temperature fluctuation from 15°C to 75°C, is the normal range encountered for liquid water in air pollution control. There is only a 2.5% difference in density for water at these two temperatures. In summary, the usual difference in water density encountered in air pollution control is less than about 2.5% and is often much less. Therefore, density changes in liquid water can usually be ignored in calculations relating to air pollution control.
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#2
- How does each of the following actions affect the density of a
liquid?
- Adding more dissolved solids into the liquid
- Adding more suspended solids to the liquid
- Changing the temperature
- Changing the pressure
- Adding more dissolved solids into the liquid
- Answer: i. Adding more dissolved solids to a liquid will increase
the density since the mass increases in relation to the volume.
- Answer: ii. Adding more suspended solids to a liquid may increase
or decrease the density of the liquid. If the density of the suspended
solids is less than the density of the liquid, then the volume
of the liquid will increase more than the mass and the density of the
mixture will decrease. If the density of the suspended solids is greater
than the density of the liquid, then more mass is being added than volume
and the density of the mixture will increase.
- Answer: iii and iv. As stated earlier the temperature and pressure of a liquid do not significantly alter the volume of liquids for the range of interest in air pollution control.