Which one of the following is a chemical change? Give reason also.
$A$. Burning of wax
$B$. Melting of wax

$A$ metal $X$ acquires a green colour coating on its surface on exposure to air.
$(i)$ Identify the metal $X$ and name the process responsible for this change.
$(ii)$ Name and write the chemical formula of the green coating formed on the metal.
$(iii)$ List two important methods to prevent this process.

$A$ silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
$(a)$ Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
$(b)$ Name the black substance formed and give its chemical formula.

Which one is a chemical change: Fermentation of fruit juice or diluting fruit juice?

In which of the following chemical equations,the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

State one basic difference between a physical change and a chemical change.