Question

the same substance can undergo a physical change or a chemical change depending upon the conditions. Explain with an example​

Answer 1

CANDLE IS BEST EXAMPLE...

The melting of wax is a physical change but burning of wax is a chemical change. So, the same substance wax can undergo both physical and chemical change. On melting, only change in the state of wax occurs but on burning wax, it produces carbon dioxide gas, water vapour, soot, heat and light.

others example...

EXAMPLE ----

it's is in physics change. No chemical bonds have been altered: H₂O(l) → H₂O(g)

Your argument is logically unsound. Although bubbles can indicate chemical change, they don't have to. It merely shows that a gas has formed. The substance is new in that it has a different state, but it's not new in terms of its chemical bonds. You still have covalent bonds between hydrogen and oxygen.