What is the physical state of dna after being denatured by heat?

The answer would be single-stranded

When DNA denaturated, the hydrogen bonds will be separated. This cause the DNA structure becomes single stranded.

Heating DNA is used for replicating DNA (PCR) because as the DNA unwinded it is exposed and the enzyme to synthesize nucleic acid bind into it.

I believe when DNA is denatured by heat, hydrogen bonds are separated to create single stranded DNA. When the DNA solution is heated enough, The double stranded DNA unwinds, and the Hydrogen bonds that hold the two strands together weaken and finally break. The process of breaking a double-stranded DNA into single strands is known as DNA denaturation, or DNA melting.