Which one of the following is a physical change?
[amp_mcq option1=”Burning of coal” option2=”Burning of wood” option3=”Heating of a platinum crucible” option4=”Heating of potassium chlorate” correct=”option3″]
This question was previously asked in
UPSC CDS-1 – 2017
– Burning of coal and wood are combustion reactions where the substance reacts with oxygen to form ash, carbon dioxide, etc. These are chemical changes.
– Heating of potassium chlorate (KClO₃) typically refers to its thermal decomposition, which produces potassium chloride (KCl) and oxygen (O₂). This is a chemical change.
– Heating a platinum crucible: Platinum is a very noble (unreactive) metal. Heating it, even to high temperatures in air, usually only changes its temperature or potentially causes thermal expansion or changes in its physical state (if heated to melting point). It does not readily undergo a chemical reaction or decomposition under normal heating conditions in a lab. Therefore, heating a platinum crucible is primarily a physical change.