Galilean thermometer

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(C)Properties of Heat and Matter - C+75: Thermometry

This thermometer has sealed glass bulbs with varying amounts of water and air inside of them floating within a container of ethanol. Since ethanol’s density changes fairly dramatically with response to temperature the balls will rise and fall accordingly as the temperature of the room changes. The one that is free-floating indicates the current temperature by means of an attached tag. A hairdryer and/or ice bath can be provided to show the motion of the bulbs due to temperature change.
UCB Index: 
C+75+25
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Comments

James Little

Tue, 07/09/2019 - 10:14

If the temperature of the room is decreased: 1. The one who is floating will sink, some of the ones at the bottom will rise. 2. The one that is floating will rise, some at the bottom will sink. 3. The one that is floating will sink, some of the ones at the bottom will sink. 4. The ones that is floating will rise, some at the bottom will rise.

James Little

Tue, 07/09/2019 - 11:01

The bulbs are sealed with a set amount of air and water. Consider the termomenter heating up: 1. When the temperature increases the air expands, compresses the water, and the density of the bulbs change and that changes where they float. 2. When the temperature increases the water in the bulbs expands, changes the density inside the bulb, and that changes where they float. 3. When the temperature increases the density of the fluid surrounding the bulbs changes and that causes the bulbs to rise or fall.

James Little

Thu, 07/18/2019 - 14:35

The first questions correct answer is 4 and the second questions correct answer is 3. The colored water in the bulbs is almost incompressible, like all water, but the fluid they are floating in is not water at all but a kind of alcohol that does have a noticeable change of density as temperature changes.