Answer: The new pressure is 3 psi.
Explanation:
Given:
= 12 psi, 
= ?, 
Formula used is as follows.

Thus, we can conclude that the new pressure is 3 psi.
When the temperature increases, the kinetic energy of the particles increase this inturn makes them vibrate
Answer:
b
Explanation:
A pure substance has a constant composition and cannot be separated into simpler substances by physical means. There are two types of pure substances: elements and compounds.
Answer:
Ionic
Explanation: Ionic compounds tend to be hard and brittle while covalent compounds tend to be softer and more flexible.
Hope this helped!