Question

honors chemistry—unit 2 video guide the race for absolute zero answer the following questions about the video. if necessary, refer to the transcripts online at http://www.pbs.org/wgbh/nova/transcripts/3501_zero.html 1. what modern conveniences exist because of “cold?” 2. what is the coldest place on earth? how cold can it get there? 3. who was james dewar? what did he invent? 4. why were oxygen, nitrogen, and hydrogen called “permanent gases?” 5. what basic process did omnes and dewar use in their attempts to liquefy hydrogen? 6. why is the process of liquefying gases so dangerous? 7. after successfully liquefying hydrogen, why wasn’t dewar’s accomplishment celebrated? 8. why did dewar give up on trying to liquefy helium? what eventually happened to omnes? 9. with respect to scientific competition, what is meant by the statement “the goalposts move as you’re playing the game?”

Explanation:

1. Modern conveniences due to "cold" might include refrigerators for food - preservation, freezers for long - term storage, and MRI machines which use superconducting magnets cooled by liquid helium.
2. The coldest place on Earth is Antarctica, with temperatures reaching as low as about - 128.6°F (- 89.2°C).
3. James Dewar was a Scottish chemist and physicist. He invented the Dewar flask, a double - walled vacuum flask used for storing very cold liquids.
4. Oxygen, nitrogen, and hydrogen were called "permanent gases" because they resisted attempts at liquefaction for a long time due to their low boiling points and the need for very low temperatures and high pressures.
5. Omnes and Dewar likely used the process of adiabatic expansion, where a gas expands rapidly and cools down, to attempt to liquefy hydrogen.
6. Liquefying gases is dangerous because the gases are often highly flammable (like hydrogen), and the low temperatures can cause materials to become brittle and break, leading to leaks. Also, rapid evaporation of the liquefied gas can displace oxygen in an enclosed space, causing asphyxiation.
7. Dewar's accomplishment might not have been celebrated because someone else may have made a similar or more significant discovery around the same time, or there could have been issues with priority or recognition in the scientific community.
8. Dewar gave up on liquefying helium possibly due to the extreme difficulty in achieving the very low temperatures required. Omnes may have faced set - backs or run out of resources in his attempts.
9. In scientific competition, "the goalposts move as you're playing the game" means that as new discoveries are made or new techniques are developed, the standards or requirements for what is considered a significant or winning discovery change.

Answer:

1. Refrigerators, freezers, MRI machines.
2. Antarctica; about - 128.6°F (- 89.2°C).
3. Scottish chemist and physicist; Dewar flask.
4. Resisted liquefaction due to low boiling points and need for extreme conditions.
5. Adiabatic expansion.
6. Gases are flammable, low temperatures make materials brittle, evaporation can displace oxygen.
7. Similar or more significant discovery by others, issues with priority.
8. Extreme difficulty for helium; set - backs or resource issues for Omnes.
9. Standards for significant discovery change as science progresses.