Question

Some substances, such as carbon dioxide change from a solid to a gas when heated, without becoming liquid in between. This is known as

• A. combustion
• B. evaporation
• C. sublimation
• D. condensation

Answer 1

Answer:

C. sublimation

• During sublimation, a substance transitions directly from the solid phase to the gas phase (or vice versa, sometimes referred to as deposition or desublimation) without passing through the intermediate liquid state.

• This process occurs because the vapor pressure of the solid exceeds the surrounding pressure at a temperature below the substance's melting point.

• Molecules at the surface of the solid gain enough thermal energy to overcome the intermolecular forces holding them in the crystal lattice, escaping directly into the atmosphere as a gas.

• Common examples include dry ice (solid carbon dioxide) and solid iodine.