[writer.at.heart415]

Which of the following descriptions of phase changes are properly matched?

a: sublimation - gas --> solid - endothermic

b: condensation - gas--> liquid - exothermic

c: freezing - liquis --> solid - endothermic

d: all of the above

e: none of the above

I chose c but it was wrong. I'm positive it's not a, because sublimation is solid --> gas, and that also eliminates d because it can't be none of the above, but which is it? Does anyone know the answer and why?

[rabolisk]

Does it require net energy to freeze something? Or is net energy given off? Likewise, does it require net energy to condense (gas to liquid) something or is net energy given off?

[writer.at.heart415]

Does it require net energy to freeze something? Or is net energy given off? Likewise, does it require net energy to condense (gas to liquid) something or is net energy given off?

I don't know. What's the answer?

[rabolisk]

I don't know. What's the answer?

That's something you should've learned, or need to review. Energy is given off when freezing something (almost always, I think there is one exception in the entire universe), and condensing. You can reason this out. To freeze or condense something, I have to lower temperature. Higher temperature promotes the opposite.

[writer.at.heart415]

I don't know. What's the answer?

That's something you should've learned, or need to review. Energy is given off when freezing something (almost always, I think there is one exception in the entire universe), and condensing. You can reason this out. To freeze or condense something, I have to lower temperature. Higher temperature promotes the opposite.

So would it be b, then? Because condensation is when gas turns into a liquid, and it releases heat, which is what an exothermic reaction does?

[rabolisk]

Yes, that is correct.