Thermometer2

= Make a Thermometer 2 =

|| || 1. Remove the jar's label. 2. Remove the top from the jar make a small hole (just big enough so the straw can fit in).
 * **Materials**
 * Rubbing Alcohol
 * Water
 * Cylinder shaped clear jar or bottle (bottles with a narrow neck work best)
 * 1 straw
 * Modeling clay
 * Food coloring
 * Marker
 * Ruler
 * Procedure**

3. Pour equal amounts of cold water and rubbing alcohol into the jar/bottle, filling it to about 1/4 of the container.

4. Add two - three drops of food coloring. 5. Insert the straw in the jar/bottle so that the bottom of the straw is submerged in the liquid but not touching the bottom of the container.



6. Seal the top of the bottle with the modeling clay so that it has a tight seal and so the straw stands upright. More clay is better than less when trying to create a seal. Mold the clay upright and shape it as if packing the straw within a volcano so that more is at the bottom and less is at the top. Make sure there are no holes. Test the seal by blowing into the straw in the jar. If the seal is tight, you will feel pressure. If not, you have a leak.

7. Use a ruler and a marker to add graduated lines on the outside of the jar every five centimeters to measure the height the liquid rises.



**How Does it Work?** Test your thermometer. Grasp the jar/bottle with your hands and hold on for 5 five minutes. What happens Describe to the best of your ability how this device actually measures air pressure. Include the following terms in your description: pressure, expansion, contraction, density.
 * 1) Place your thermometer in a pan of cold water. What happens?
 * 2) Place your thermometer in a pan of hot water. What happens?

When we heat the liquid, the temperature of the liquid increases. The liquid changes its physical state to a vapor. The vapor pressure increases above the liquid. When the vapor pressure inside the closed system exceeds the atmospheric pressure outside the jar, it will force the liquid to displace or move. Since the liquid cannot go anywhere, but up, the liquid rises up the straw.

What can you do to improve the functioning of this device? Can you improve the accuracy? Precision? Can you make the device more stable or portable? You may select any materials we have here today or suggest alternative materials. Be clear in your description as to why these modifications will improve this device.
 * Engineering Experience: Ideas for Improving the Design**

Questions to ask the students:

How do you think the liquid would respond if you: a. if you performed the experiment on a mountain? b. performed the experiment when the room temperature is either colder or hotter than your first round? c. performed the experiment on a cloudy or sunny day? d. used water only instead of alcohol? used honey instead of alcohol? e. if the thinkness of the straw changes? f. if there is a full moon? g. did not use clay to seal the straw? h. add more liquid or less liquid? i. did not heat up the liquid? j. raise or lower the straw?