. A student observes what happens when two different aqueous solutions are mixed in a test tube. Which of the following observations would be most indicative of a precipitation reaction?
Gas bubbles are produced.
There is a color change.
The test tube warms.
A solid settles out.

a solid settles out

Explanation:

a precipitate is when a solid forms

the number of protons in the nucleus of a given element. has slight luster and conducts electricity at high temperatures like metal.but like a nonmetal,boron is brittle and does not conduct electricity well at low temperatures. in graphite, carbon is a soft,brittle solid.it is reflective,ductile,or malleable.