An ornamental thermometer, commonly known as a Galileo thermometer, contains a number of spheres of hollow colored glass, representing different temperatures, immersed in a column of ethanol. A particular sphere rises from the bottom to the top of the column of liquid when the temperature falls below the value it represents. Which statement best explains why the sphere rises when the temperature falls?
A. The density of the liquid has increased.
B. The mass of the sphere has decreased.
C. The pressure exerted by the liquid has decreased.
D. The temperature of the sphere is different from that of the liquid.
E. THe volume of the gas inside the sphere has decreased.
Now think!
Did the mass of the sphere change? Was it a nuclear reaction?
What dos the fluid pressure have to do with good old Archimedes?
How long would the temperature of the sphere and the fluid stay different? LOL
How did the volume inside the sphere change if the glass did not shrink ?
The correct answer is C. The pressure exerted by the liquid has decreased.
In a Galileo thermometer, the spheres are filled with a liquid or gas that expands or contracts with changes in temperature. When the temperature drops, the liquid or gas inside the spheres contracts, causing the pressure inside the spheres to decrease. As a result, the pressure exerted by the liquid surrounding the spheres becomes relatively higher, causing the spheres to rise in the column of liquid.
The correct answer is A. The density of the liquid has increased.
To understand why the sphere rises when the temperature falls, we need to consider the principle behind the Galileo thermometer. The spheres inside the thermometer are each filled with a specific amount of liquid, usually ethanol, and have a small attached tag indicating a specific temperature. The spheres are carefully calibrated so that each one represents a different temperature.
The principle at work is that the density of a liquid, such as ethanol, changes with temperature. As the temperature of the ethanol decreases, its density increases. The spheres inside the thermometer are designed to have a slightly lower density than the surrounding liquid, so they will float. However, as the temperature decreases, the density of the ethanol increases and eventually becomes greater than that of the sphere.
When this happens, the sphere will start to sink because it is now denser than the liquid. On the other hand, if the temperature rises, the density of the liquid decreases, causing the sphere to be less dense than the liquid, allowing it to float.
So, when the temperature falls, the density of the liquid increases, causing the sphere to become less dense than the liquid, and it rises from the bottom to the top of the column of liquid to reach a level where its density matches that of the surrounding liquid.