Final answer:
Curly hair appears shorter after drying due to the shrinkage effect, where water disrupts hydrogen bonds in keratin strands, causing them to reform into curls or waves as they dry. This is a physical change in the hair structure.
Step-by-step explanation:
Curly hair can appear shorter after it dries because of a shrinkage effect. This shrinkage is due to the propensity of wet hair to disrupt hydrogen bonds in keratin strands, allowing the strands to temporarily reform into curls or waves as they dry. Hair cuticle cells expand when they absorb water, but as hair loses moisture to the air, these strands contract and cause curly or wavy hair to draw up and appear shorter.
Both temporary and permanent waves result from disruptions to hydrogen and disulfide bonds within hair. Temporary waves occur as new hydrogen bonds are formed during the drying process, while permanent waves involve the use of chemicals to break and reform disulfide bonds for a longer-lasting effect. These changes are physical, not chemical, because the structure of keratin itself is not chemically altered during the styling process.