Question

1. both boiling and evaporation are processes where a liquid changes into a gas. what is the key difference between them?

• boiling occurs only at the surface of a liquid, evaporation occurs throughout the liquid.
• boiling requires a decrease in temperature, while evaporation requires an increase (text cut off)
• evaporation is a faster process than boiling.
• boiling is specific temperature given pressure, evaporation is ranges of temperatures.

1. sublimation is the phase change where a substance transitions directly from a solid to a gas without becoming a liquid. which of the following substances is known to readily undergo sublimation at standard atmospheric pressure?

• ethanol
• carbon dioxide (dry ice)
• iron
• water

Explanation:

Question 3

• Analyze each option:
• First option: Incorrect. Evaporation occurs at the surface, boiling throughout the liquid.
• Second option: Incorrect. Both boiling (at boiling point, constant temp) and evaporation (can occur at various temps) don't match this.
• Third option: Incorrect. Boiling is faster as it's bulk, evaporation is surface - slow.
• Fourth option: Correct. Boiling happens at a specific temp (boiling point) for a given pressure. Evaporation can occur over a range of temps (even below boiling point) as it's a surface - based process.

• Recall sublimation examples:
• Ethanol: Liquid at STP, evaporates, no sublimation.
• Carbon dioxide (dry ice): At standard atmospheric pressure, dry ice (solid $CO_2$) sublimes directly to gaseous $CO_2$.
• Iron: Solid metal, requires very high temp/pressure changes, no sublimation at STP.
• Water: At STP, solid water (ice) melts to liquid first, doesn't sublime readily (sublimation of ice is slow and called frost - free or at very low pressures).

Answer:

Boiling is specific temperature given pressure, evaporation is ranges of temperatures.

Question 4