ICSE Class 9 Chemistry – Chemical Changes, Reactions & Water

20 fill-in-the-blank flashcards covering key definitions, equations, properties, and concepts from ICSE Class 9 Chemistry Chapters 2 & 3.

A chemical change is a __ change in which the original substance is transformed into new substance(s).

permanent

One feature of a chemical change is an __ change, where heat or light may be released or absorbed.

energy

Chemical reactions are represented by .

chemical equations

In a combination reaction, two or more substances combine to form a __ product.

single

A decomposition reaction usually requires heat, light, or __ to break down a compound.

electricity

In a displacement reaction, a __ reactive element displaces a less reactive element from its salt solution.

more

A double displacement reaction often produces an insoluble solid called a __.

precipitate

Reactions that release heat are called __ reactions.

exothermic

Photosynthesis is an example of an __ reaction because it absorbs heat (sunlight).

endothermic

Rust is chemically known as __ iron (III) oxide.

hydrated

A balanced chemical equation obeys the Law of __ of Mass.

Conservation

A chemical change is usually __.

irreversible

Pure water contains about __% oxygen by weight.

88.9%

Temporary hardness of water is caused by calcium or magnesium __.

bicarbonates

Permanent hardness can be removed by adding washing soda, chemically known as .

sodium carbonate

Water is called a because it dissolves many substances.

universal solvent

Water has maximum density at __ °C.

4

According to the Law of Conservation of Mass, total mass of reactants __ total mass of products.

equals

During electrolysis, water decomposes into hydrogen and __ gases.

oxygen

The change of water vapour into clouds is called __.

condensation