Unit-7 Density and Temperature
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Unit-7 Density and Temperature
Answer: Volume = 78/7.8 = 10 cm^3.
Answer: alpha = expansion/(original length x temperature rise) = 0.4/(100 x 200) = 2 x 10^-5 per degree C.
Answer: A hydrometer floats in the liquid and its depth of sinking gives the relative density.
Answer: Its density is greater than that of water, so it sinks.
Answer: Increase = alpha x L0 x temperature change = 1.2 x 10^-5 x 100 x 100 = 0.12 cm.
Answer: Heating air expands it, so its density falls and it becomes lighter than the surrounding air.
Answer: Compressing a gas reduces its volume at constant mass, so density rises.
Answer: Using F = (9/5)C + 32, solving C = (9/5)C + 32 gives C = -40.
Answer: Heating increases volume while mass stays the same, so density falls.
Answer: Relative density equals the density in g/cm^3, since water density is 1 g/cm^3.
Answer: For the same length and temperature rise, the material with the larger coefficient of linear expansion expands more.
Answer: Pure water freezes at 0 degrees C, the lower fixed point of the Celsius scale.
Answer: 1000 kg/m^3 is the same as 1 g/cm^3.
Answer: Multiply by 1000 to convert g/cm^3 to kg/m^3, giving 2500 kg/m^3.
Answer: Mercury solidifies at -39 degrees C, so an alcohol thermometer, which freezes much lower, is used for very cold regions.
Answer: Relative density compares a substance with water itself, so water has relative density 1.
Answer: Mass = density x volume = 7.8 x 1000 = 7800 g.
Answer: Water has maximum density at 4 degrees C, so equal volume at 4 degrees C contains more mass.
Answer: Iron has a density of about 7800 kg/m^3, i.e. 7.8 g/cm^3.
Answer: Mercury has density 13.6 g/cm^3, so its relative density is 13.6.