Differences

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--- demonstrations:1_mechanics:1r_properties_of_matter:elasticity_of_glass:start [2019/03/21 18:20] – created demoroom
+++ demonstrations:1_mechanics:1r_properties_of_matter:elasticity_of_glass:start [2019/03/21 21:27] (current) – demoroom
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 ====== Elasticity of Glass ======
-{{tag> needs_review untagged unlocated}}
+{{tag> glass elasticity properties_of_matter strain volume capillary_tube unlocated}}
 <WRAP box right>
-{{default.jpg?400|}}
+{{full_bottle.jpg?400|}}
-// Comment here //
 </WRAP>
 ===== Description =====
-A short description of what the demonstration consists of, what it looks like, etc.
+This demonstration consists of a glass bottle filled with water that's been dyed dark blue. The top of the bottle is stopped with a rubber stopper, and a glass capillary tube (formerly part of a thermometer) is stuck into the stopper.
 ===== Purpose =====
-What is the purpose of the demonstration? What concepts does it demonstrate, how would it be used in a class?
+This demonstration shows the elasticity of a material usually thought of as brittle and inflexible. Demonstrates the measurable strain produced in glass as a result of force exerted by squeezing the bottle.
 ===== Apparatus =====
-  * Complete bullet-point listing of the materials required to run the demonstration.
+  * Bottle with capillary tube and strongly dyed water
-  * Particularly including anything that isn't stored with the demo.
+  * Water and an eye dropper (if necessary)
-  * If something listed here has a page elsewhere on the site be sure to make it a link.
 ===== Setup =====
-What steps are necessary to set up the demonstration? Is there any preparation that must be done ahead of time? Are there any things that the person setting it up should bear in mind, any potential problems that may need to be solved? Finally, are there any things that may be optionally done to 'go beyond' the basic setup?
+  * First you should check that the water level is correct. Ideally when running the demonstration the level of the water should be approximately halfway up the capillary.
+  * If the water level is too high, squeeze the flat sides of the bottle together until the excess water beads up at the top of the capillary tube. Use a tissue to absorb the excess, repeating if necessary.
+  * If the water level is too low (or not visible at all) things get a bit more difficult. Squeeze the flat sides of the bottle together and use the eye dropper to place a droplet of water on the end of the capillary tube.((If possible, try to add the droplet on top when the level of water inside the capillary reaches the top. This'll prevent the formation of bubbles, which are a bit annoying to get rid of.)) Release it, and then squeeze the high sides of the bottle together to draw the water in further. Repeat if necessary.((After adding water you might find that the newly added water is lightly colored because it hasn't mixed much with the rest of the strongly dyed water. This can be remedied by repeatedly squeezing the bottle so that the water in the capillary mixes with the rest of the water in the bottle.))
+  * If any bubbles developed, squeeze the bottle until they are pushed out the top.
+  * Once the water level is at desired level, the demonstration can be shown. By squeezing the flat sides of the bottle together, you'll decrease the internal volume of the bottle and can thus raise the water level. By squeezing the raised sides of the bottle (perpendicular to before) you can increase the volume of the bottle and lower the water level.
 ===== Notes =====
-Any additional notes that don't fit in the above sections can go here. Helpful links, background information, whatever you feel like adding.
+This demonstration can be finicky at times, you may notice that the water level will increase even as you hold it.
-<WRAP danger>
+Only a very small change in the volume of the liquid is necessary to produce a substantial change in the height of the liquid in the capillary tube, so it's very sensitive to the environment. This effectively means that, in addition to providing an effective reading of the small changes in volume of the bottle, it's also an effective thermometer and barometer.
-Safety notes can also be added here or in the description. Use this one if theres a potentially fatal hazard like high voltage,
-</WRAP>
-<WRAP caution>
+The bottle has an internal volume of 375ml, and the visible part of the capillary tube has a length of 7.5cm and an internal diameter of 0.3mm. (somewhere between 0.25mm and 0.5mm, this is a guess.) This means that to go between the capillary being empty and the capillary being full, there must be a reduction of the bottles volume of 5.3 microliters, or a change of 0.00141%.
-and this one can be used for less frightening things.
-</WRAP>
+If you do some math, you'll find that to achieve a similar change via expansion due to heating an increase in temperature of only 0.068ºC is required.((This is neglecting the thermal expansion of the glass, which should act against this change. That value is about ten times less than the value for water though, so I chose to ignore it. The actual change in temperature required should be ~10% higher.))
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-{{default.jpg?400|}}
+{{bottle_top_detail.jpg?400|}}
-// Comment here //
+// Detail showing the top of the bottle and the capillary tube sticking out. //
 </WRAP>
 </WRAP>
 <WRAP half column>
-<WRAP box right>
-{{default.jpg?400|}}
-// Comment here //
-</WRAP>
 </WRAP>
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 <WRAP centeralign> // Demo room information //
 </WRAP>
-<WRAP tablewidth 100
+<WRAP tablewidth 100%>
 | **Location** | ---- |
 | **Maker** | Unknown |