CHEMISTRY COMMUNITY

how can you tell if there has been a phase change?

Usually the problem will tell you when a phase change occurs, or if on a phase diagram the temperature remains constant but enthalpy increases, the energy in crease was used for the phase change of the compound.

Like the diagram in class, you can tell that there is a phase change when the heat or enthalpy is increasing, but the temperature is not increasing, or delta T is zero.

Sanjana Borle 2K wrote:Like the diagram in class, you can tell that there is a phase change when the heat or enthalpy is increasing, but the temperature is not increasing, or delta T is zero.

Can the enthalpy increase AND the temperature remains the same while there still not being a phase change? Like I'm imagining the enthalpy of water at a positive value but without becoming a gas? Is that possible?

KBELTRAMI_1E wrote:

Sanjana Borle 2K wrote:Like the diagram in class, you can tell that there is a phase change when the heat or enthalpy is increasing, but the temperature is not increasing, or delta T is zero.

Can the enthalpy increase AND the temperature remains the same while there still not being a phase change? Like I'm imagining the enthalpy of water at a positive value but without becoming a gas? Is that possible?

I was wondering the same thing. Would any change in either of these, no matter to what degree, result in a phase change? Or is there an explicit threshold for each phase with regards to the reaction?

Ivan Tadeja 1G wrote:

KBELTRAMI_1E wrote:

Sanjana Borle 2K wrote:Like the diagram in class, you can tell that there is a phase change when the heat or enthalpy is increasing, but the temperature is not increasing, or delta T is zero.

Can the enthalpy increase AND the temperature remains the same while there still not being a phase change? Like I'm imagining the enthalpy of water at a positive value but without becoming a gas? Is that possible?

I was wondering the same thing. Would any change in either of these, no matter to what degree, result in a phase change? Or is there an explicit threshold for each phase with regards to the reaction?

I believe because enthalpy is a state function there are explicit thresholds for each phase which is why, when plotted, it is a step diagram. That is how I understood it, there could be a different explanation

Julia Holsinger_1A wrote:

Ivan Tadeja 1G wrote:

KBELTRAMI_1E wrote:
Can the enthalpy increase AND the temperature remains the same while there still not being a phase change? Like I'm imagining the enthalpy of water at a positive value but without becoming a gas? Is that possible?

I was wondering the same thing. Would any change in either of these, no matter to what degree, result in a phase change? Or is there an explicit threshold for each phase with regards to the reaction?

I believe because enthalpy is a state function there are explicit thresholds for each phase which is why, when plotted, it is a step diagram. That is how I understood it, there could be a different explanation

That is how I initially believed it to be. Are all diagrams for phase changes step diagrams?