This document discusses physical and chemical changes. It defines change as something becoming different or taking another form. Physical changes alter a substance's physical properties but do not form new substances, while chemical changes produce new substances through chemical reactions. An example of a chemical change given is rusting of iron, which occurs through a reaction of iron with air and water to form iron oxide. The document also describes ways to prevent rusting, such as through galvanization which deposits a zinc layer on iron, and alloying iron with corrosion-resistant metals like in stainless steel.

1. PHYSICAL AND
CHEMICAL CHANGE
BY : MISS RITIMA
(APS RAKHMUTHI )
CLASS: VII

2. WHAT DO YO MEAN BY
CHANGE?
THE WORD CHANGE
MEANS TO BECOME
DIFFERENT OR TO TAKE
SOME OTHER FORM.

3. TYPES OF CHANGES
PCHEMICAL CHANGE
HYSICAL CHANGE

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.

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.

11. RUSTING OF IRON

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.

15. HOW TO PREVENT
RUSTING
BY GALVANISATION
BY ALLOYING

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.

17. IRON WITH LAYER OF ZINC -
GALVANISATION

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.