Chemical Change is a process in which a substance combines with another to form a new substance by chemical reactions.
In the above given process, new products are formed after a chemical reaction in which the products are reversible.
However, in burning, a new substance is formed which is irreversible.
Example: Ash is formed after burning wood, Carbon dioxide and water are formed after burning methane gas in air, etc.
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A chemical change occurs when one substance gets converted into another due to a chemical process. This change is very often not reversible.
Among the given options, the process that causes a chemical change is 2) burning. When a substance is burnt, it cannot be restored to its original form. For example, when a paper is burnt, it is converted to ashes. It is not possible to reconvert the ash into paper.
ENERGY May be given out or absorbed during chemical change .
So, among the above given options:
Burning involves chemical changes.
Burning of candle:
Candle burns to give heat , light energy along with water vapour and CO2.
It's irreversible change.
Remaining options are physical change examples
"for a fixed mass of gas, at a constant volume, the pressure (p) is directly proportional to the absolute temperature (t)."
pressure ∝ temperature
pressure/ temperature = constant