A Galileo thermometer consists of a cylinder filled with a known solution and several sealed glass bulbs partially filled with water. Each bulb effectively acts as an isolated system. If one of the bulbs has the same density as the solution at 25 °C, how will its position and the density of the solution change as the temperature of the solution decreases from 25 °C to 20 °C?

Question

A Galileo thermometer consists of a cylinder filled with a known solution and several sealed glass bulbs partially filled with water.  Each bulb effectively acts as an isolated system.  If one of the bulbs has the same density as the solution at 25 °C, how will its position and the density of the solution change as the temperature of the solution decreases from 25 °C to 20 °C?

Quizplus · Accepted Answer

11ecba2d_11dc_2fcc_a3bf_97f430d6df9d_MD0008_00 The density of a substance is defined as the mass it contains per unit of volume it occupies. The exact density of a substance, however, can slightly vary with temperature due to minute changes in volume because materials tend to expand when heated and contract when cooled. Materials also physically arrange according to density. For example, when a solid object is placed into a liquid, the object will float if it has a density less than that of the liquid, but it will sink if its density is greater than that of the liquid. Initially, at 25 °C, the mass-to-volume ratio (density) of the sealed glass bulb exactly matches that of the solution in the cylinder. As the temperature of the solution in the cylinder decreases, the density of the solution increases (same mass occupying a contracted volume). Because the glass bulb acts like an isolated system, its density changes very little compared with that of the cylinder solution. Accordingly, the density of the cooling solution in the cylinder becomes greater than that of the bulb, causing the bulb to begin to float. This is the basis for the function of the Galileo thermometer. (Choices A and B) As the temperature of a liquid decreases, it contracts and slightly decreases the volume of the given liquid mass. Therefore, the density of the solution in the cylinder will increase with decreasing temperature. (Choice C) As the temperature of the solution decreases, its density increases and becomes denser than the bulb. Objects that are less dense than the solution will float in the solution. Educational objective: The density of a substance is defined as the mass it contains per unit of volume that it occupies. The exact density of a substance can vary slightly with temperature due to minute changes in volume caused by the expansion or contraction of materials. Solid objects float in liquids with a higher comparative density and sink in liquids with a lower comparative density.

A Galileo Thermometer Consists of a Cylinder Filled with a Known