Which Easily Observed Molecular Species Is Used as a Tracer

question 8

Multiple Choice

Which easily observed molecular species is used as a tracer for the fundamental but difficult to observe H₂ molecules in giant molecular clouds?

• A) hydroxyl (OH)
• B) water vapor (H₂O)
• C) carbon dioxide (CO₂)
• D) carbon monoxide (CO)

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Definitions:

Eutectic Alloy

A mixture of two or more metals that solidifies at a single temperature, the lowest at which the mixture can remain fully solid, forming a homogeneous crystal structure.

Heater Barrel Element

A heating component used in machines such as injection molding machines, responsible for heating the barrel in which plastic is melted.

Liquid State

A phase of matter characterized by a definite volume but no definite shape, assuming the shape of its container.

Dropout Current

The minimum current at which a relay, contactor, or coil will de-energize, allowing its contacts to return to their default state.