Which of these undergoes physical change? why?

Question

a dry leaf is crushed

grass in the yard is cut

chemistry book is burned

a bar of copper is formed into wire

rusting of iron

if it doesnt undergo physical change, then why does it undergo chemical change?

please explain your answers. the explanation is more important. PLEASE explain it in FULL and DETAILED.

thank you.

Answer 1

*...A crushed dry leaf is simply fragments of the same substance and is a Physical Change....No Chemical Reaction.

*...Cut grass is still grass...Physical...no Chemical change.

*...Burning is a Chemical reaction. The book (paper) is a fuel and burning is a chemical reaction forming new substances...CO2, C (Black Carbon remnants) and Water vapour.

*...Copper extruded to a length of wire remains as Copper...same substance...Physical change.

*...Rusting is like a very slow combustion process where the Iron becomes Oxidised to Red Iron Oxide Hydrate ...Fe2O3.xH2O....A Chemical Reaction.

(' x ' represents a varying amount of water).

Answer 2

One simply divides the dry leaf substance into smaller pieces

The same for "Leaves of Grass"

A polymer of glucose called cellulose reacts with oxygen to form CO2 + H2O

A big one is made into a long, narrow one.

Iron reacts with oxygen to form iron(III) oxide. It is unwise to try to erect tall structures using iron(III) oxide.