The process that separates DNA strands by increasing temperature is called denaturation.
DNA’s two strands are held together mainly by hydrogen bonds between complementary bases and by base-stacking interactions. When DNA is heated, molecular motion disrupts these interactions, causing the double helix to separate into single strands. This thermal process is known as DNA denaturation, or melting.
The temperature at which about half of a DNA sample is denatured is called its melting temperature, or Tm. It depends on factors such as DNA length, salt concentration and base composition. DNA regions rich in guanine and cytosine generally require more heat to melt because G–C pairs form three hydrogen bonds, while A–T pairs form two.
Denaturation is reversible if the strands are cooled under suitable conditions. They can pair again through annealing, also called renaturation. In laboratory PCR, repeated heating separates the template strands, while cooling allows short primers to bind. Hybridization is the broader pairing of complementary nucleic-acid strands, not the heat-driven separation itself.