Classify the following changes as desirable changes or undesirable changes:

S.No	Example	Desirable/Undesirable Change	Reason
1.	Occurrence of rain	_____	_____
2.	Cutting trees in the forest	_____	_____
3.	Changing the course of rivers to build dams	_____	_____
4.	Formation of manure from cow-dung	_____	_____
5.	Contamination of food	_____	_____
6.	Increase in the population of fishes	_____	_____
7.	Release of smoke from industries	_____	_____

Identify the following as physical change or chemical change:

Classify the following change as slow or fast, reversible or irreversible, desirable or undesirable, cyclic or non-cyclic, physical or chemical changes-

Formation of phases of moon.

Classify the following change as slow or fast, reversible or irreversible, desirable or undesirable, cyclic or non-cyclic, physical or chemical changes-

Lightening in the sky

Classify the following change as slow or fast, reversible or irreversible, desirable or undesirable, cyclic or non-cyclic, physical or chemical changes-

Formation of natural gas from cow dung.

Classify the following change as slow or fast, reversible or irreversible, desirable or undesirable, cyclic or non-cyclic, physical or chemical changes-

Combustion of petrol in a vehicle.

Classify the following change as slow or fast, reversible or irreversible, desirable or undesirable, cyclic or non-cyclic, physical or chemical changes-

Formation of curd from milk.

Fill in the blanks with the word physical or chemical.

Digestion of food is a _____ change.

Fill in the blanks with the word physical or chemical.

Formation of water from ice is a _____ change.