Question

why the following are called chemical changes
(1) burning of wood
(2)rusting of iron
(3)digestion of food

Answer 1

heya folk !!!!

chemical change is a change where the reaction results in formation of new substance with different properties

in all three cases new substance is formed

so they are chemical changes

in burning of wood ash and co2 gas is released

in rusting of iron oxide ( rust ) Is formed

in digestion of food energy is produced

Answer 2

1)Burning of wood involves the chemical changes because when the wood is burnt it gives out gases, heat and ashes which means a product is formed from the reactant. So, it is called a chemical change.
2)Rusting of iron is called a chemical change because when iron get rusted it converts from Fe to Fe2O with the reaction of water and air contained in the atmosphere. So,again a new product is formed from the reactant. Hence, it is a chemical change.
3)Digestion of food involves many processes like absorption,chewing, etc. Here also a new product is formed from the reactant. So, it is also a chemical change.