Physical and chemical change class 7TH

BASIC

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.

6. 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.

7. 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.

8. RUSTING OF IRON

9. 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 .

10. HOW TO PREVENT RUSTING BY GALVANISATION BY ALLOYING

11. 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 .

12. IRON WITH LAYER OF ZINC - GALVANISATION

13. 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 .

14. 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.