CHEMISTRY COMMUNITY

How do we determine when there has been a phase change?

If the substance reaches its boiling point, melting point, or freezing point, that makes it clear the substance undergoes a phase change. In other instances, sometimes the problem will tell us that the substance, melted, froze, or evaporated.

If the temperature changes beyond the vaporization/melting point (ex. from 70 C to 110 C for water) then a phase change occurred.

When the substance reaches it’s melting/ boiling/ freezing point. Drawing the heating curve for water at least can be helpful.

I feel like usually, the problem would tell us the type of system it is along with the changes that have occurred: Melting, boiling, vaporizing, etc.

Usually when the boiling, melting, or freezing point has been reached.

What calculation do we also have to incorporate when going from a gas to a liquid or vice versa?

you know if there is a phase change if in the reaction the molecule at focus has gone from a liquid to a solid or gas, etc

Natalie Benitez 1E wrote:What calculation do we also have to incorporate when going from a gas to a liquid or vice versa?

When calculating q for the reaction you can use the phase change graph and calculate the different q for both the heating and the phase change to calculate the q for the phase change from liquid to gas or the heat that would be released when going from gas to liquid.