Unit-7 Density and Temperature
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Unit-7 Density and Temperature
Answer: 0 K is the absolute minimum temperature, so the Kelvin scale never has negative values.
Answer: The volume coefficient is about three times the linear coefficient, gamma = 3 alpha.
Answer: On heating, matter generally expands, i.e. its dimensions (length, area or volume) increase.
Answer: The metal that expands less remains on the inside, so the strip bends towards the metal of smaller coefficient.
Answer: The gaps let the rails expand on hot days without buckling.
Answer: Mercury does not stick to glass, is opaque and visible, and expands uniformly with temperature.
Answer: The metals expand by different amounts, so the strip bends when heated or cooled.
Answer: This is anomalous expansion: water expands when cooled from 4 degrees C to 0 degrees C instead of contracting.
Answer: Water is densest at 4 degrees C (1000 kg/m^3); below and above this its density decreases.
Answer: Alcohol freezes at about -114 degrees C, much lower than mercury, so it can measure very low temperatures.
Answer: From 0 to 4 degrees C water contracts on heating; above 4 degrees C it expands normally.
Answer: Ice is less dense than water, so it floats on the surface and protects the water below.
Answer: The kink holds the mercury in place after measuring, so the reading can be taken comfortably.
Answer: The upper fixed point is the boiling point of water, 100 degrees C.
Answer: The lower fixed point on the Fahrenheit scale is 32 degrees F, the freezing point of water.
Answer: Expansion joints allow bridge sections to expand and contract freely with temperature changes.
Answer: At constant volume, molecules hit the walls more frequently and harder as temperature rises, so pressure increases.
Answer: Joule is a unit of energy, not of temperature.
Answer: In a denser liquid the upthrust is greater, so the hydrometer floats higher.
Answer: Clinical thermometers use mercury because of its uniform expansion and visibility.