4. PHYSICAL CHANGE
WHEN A SUBSTANCEE
UNDERGOES A CHANGE IN ITS
PHYSICAL PROPERTIES THAT
CHANGE IS SAID TO BE
PHYSICAL CHANGE.
5. CHRACTERISTICS OF A
PHYSICAL CHANGE
ONLY THE PHYSICAL PROPERTIES OF THE
SUBSTANCE UNDERGO CHANGE.
PHYSICAL CHANGES ARE GENRALLY
REVERSIBLE.
NO NEW SUBSTANCE IS FORMED.
NO OR EITHER VERY SMALL AMOUNT OF
ENERGY IS EITHER ABSORBED OR EVOLVED
DURING PHYSICAL CHANGE.
6.
7.
8. CHEMICAL CHANGES
WHEN TWO OR MORE SUBSTANCES
REACT IN SUCH A WAY THAT THERE
IS FORMATION OF NEW SUBSTANCE,
THE CHANGE IS CALLED AS
CHEMICAL CHANGE.
A + B= C
HERE A &B ARE REACTANTS
C IS PROCUCT.
9. CHRACTERISTICS OF
CHEMICAL CHANGE
NEW SUBSTANCES WITH DIFFERENT
PROPERTIES ARE FORMED.
CHEMICAL CHANGE IS IRREVERSIBLE.
LARGE AMOUNT OF HEAT IS EITHER
EVOLVED OR ABSORBED DURING CHEMICAL
CHANGE.
14. WHAT IS RUSTING
RUSTING IS THE SPECIFIC NAME GIVEN TO
THE CORROSION OF IRON.
IT IS A CHEMICAL REACTION BETWEEN IRON,
AIR AND WATER.
RUST IS THE REDDISH BROWN COVERING ON
THE SURFACE OF IRON.
THIS REDDISH BROWN COVERING ON THE
SURFACE OF IRON IS IRON OXIDE.
16. GALVANISATION
IT IS THE PROCESS OF DEPOSITING
LAYER OF ZINC ON A IRON OBJECT.
THE ZINC FORM A LAYER OFZINC
OXIDE ON REACTION WITH AIR AND
THUS FORMS A BARRIER BETWEEN
IRON AND ATMOSPHERE.
18. ALLOYING
CERTAIN METALS CAN BE MADE
RUST FREE WHEN MIXED WITH
CORROSION RESISTANT METLS.
EG. STAINLESS STEEL IS AN
ALLOY OF IRON , NICKEL AND
CHROMIUM . IT DOES NOT
RUST.
19. CRYSTALLISATION
CRYSTALLISATION IS A PROCESS BY WHICH
PURE CRYSTALS OF A SUBSTANCE ARE
OBTAINED FROM IMPURE SUBSTANCE .
CRYSTAL SARE THE PUREST STATE OF A
SUBSTANCE.