(1.4) Changes of State (pp. 436-439)

sublimation

The change of a substance from a solid to a vapor without passing through the liquid state

Explain What do the curved lines on a phase diagram represent?

The changing point between one phase to another. Where they are together at a point. Answer: The lines show the conditions of temperature and pressure at which two phases exist in equilibrium.

How are the conditions at which phases are in equilibrium represented on a phase diagram?

The conditions of pressure and temperature at which two phases exist in equilibrium are indicated on a phase diagram by a line separating the two regions representing the phases.

Solid- sublimation- Vapor

Vapor- deposition- Solid

triple point

describes the only set of conditions at which all three phases can exist in equilibrium with one another.

phase diagram

gives the conditions of temperature and pressure at which a substance exists as solid, liquid, or gas (vapor).

Interpret Graphs Using Figure 13.18, estimate the boiling point of water at a pressure of 50 kPa.

50°C Answer: about 60 degrees celsius

Explain What does the triple point on a phase diagram describe?

It is the only condition where all three phases can exist together. Answer: The triple point describes the only set of conditions at which three phases can exist in equilibrium.

Identify What properties must a solid have to undergo sublimation?

It must be frozen and when frozen have to water vapor taken out of it. Answer: Sublimation occurs in solids that have vapor pressures that exceed atmospheric pressure at or near room temperature.

Classify Would you expect a substance that sublimates at or near room temperature to be a molecular substance or an ionic substance?

Molecular substance because it is close to changing point. Answer: The substance must be molecular. Ionic substances have very high melting points and strong bonds. Molecular substances have weak bonds.

Apply Concepts Describe one practical use of sublimation.

Shipping frozen fruits use dry ice to keep them cold which is ice that has the water vapor taken out of it. Answer: freeze-dried coffee, dry ice as a coolant, air fresheners, separating mixtures, and purifying substances

When can sublimation occur?

Sublimation occurs in solids with vapor pressures that exceed atmospheric pressure at or near room temperature.