Q12.8 P - Chemistry: Molecular Nature Of Matter And Change

Question

Name the phase change in each of these events:

(a) A diamond film forms on a surface from gaseous carbon atoms in a vacuum.

(b) Mothballs in a bureau drawer disappear over time

(c) Molten iron from a blast furnace is cast into ingots (“pigs”).

Step-by-Step Solution

Answer

1. During this process, the gaseous phase converts to the solid phase
2. Solid phase converts into the gaseous phase
3. Liquid phase conversion to the solid phase

Step 1: Forms of Carbon

Diamond is a crystalline form of carbon atoms with anisotropic properties.

Step 2: Phase transformation

When a diamond film is formed using the gaseous carbon atoms under a vacuum, the gaseous form gets converted into a solid form.

Step 3: Mothballs

Mothballs are solid balls made up of chemical pesticides and deodorants that are used for storing clothes and other materials.

Step 4: Phase conversion

Mothballs in a bureau drawer disappear because of the low value of heat of sublimation. The heat of sublimation is so low that it can be achieved even at room temperature for long hours. Thus, for long hours, the mothballs get sublimate slowly and thus disappear.

Step 5: Ingots

Ingots are blocks of metal. It is the first semi-finished casting product in the manufacturing process

Step 6: Phase Conversion

Molten iron (from blast furnace) is in the liquid phase which during casting converts to the solid phase.