1. 9TH STD.-SCIENCE & TECHNOLGY
KANYA VIDYALAYA PIMPRI WAGHERE.
POWERPOINT PRESENTATION
BY- PAWAR V.G.
9TH STD.-SCIENCE & TECHNOLGY
COUNTTING MATTER

2. UNIT :- COUNTING MATTER
SUB UNITS :-4.1..LAWS OF CHEMICAL COMBINATION
4.2- THE ATOM
4.3- MOLECULE
4.4- MOLECULAR MASS &MOLE CONCEPT
4.5 – CHEMICAL FORMULAE OF COMPOUNDS

4. Matter
Solid
Liquid
Gaseous

5. Definition
Matter-
Matter is anything around us that we can perceive through our senses.

6. Law of conservation of matter
“Matter is neither gained nor lost during a chemical reaction.” This is called the law of conservation of matter.

7. Law of constant proportion -
“In a compound, constituent elements are always present in a definite proportion by weight.” It is called the law of constant proportion.

8. Symbols The symbol of any element indicates one atom of that element.
Symbol of the element is the first letter of the name of the element or first letter and second/other prominent letter in the name.”

9. Chemical symbols of the elements
Hydrogen -
Iron ♂
Copper ©
Sulphur

10. Molecule - Molecule is made up of two or more atoms of elements.
Atoms of some elements exist
independently.
e.g.- H2 , Cl2 , O2 .

11. Molecular mass - ‘The sum of the atomic
masses of the atoms present in a
given molecule is the molecular
mass of the substance.’
e.g.- Molecular mass of Co2 = 44 and H2o= 18

12. Mole -
A collection of Avogadro’s number objects of the same type (such an atoms or molecules) is called a mole.

13. Radicals -
Atoms or group of atoms having a positive or negative charge are known as radicals.

14. Valency-
The combining capacity of an element is known as its valency .

15. Valency- 1 4 3 2
Hydrogen
Carbon
Sodium
Nitrogen
Oxygen

16. Valency-
Neon
Aluminium
Chlorine
Calcium
Magnesium - 3 1 2

17. Chemical formulae
of compounds

18. Sodium bromide - Chemical formula of Sodium bromide is NaBr.
The formula is obtain as follows –
Symbol of Sodium is - Na &
Symbol of Bromine is – Br.

19. Now,
The valency of Sodium is +1
& The valency of bromine is -1.
Cross multiply the valencies
Na Br
The formula of sodium bromide
is NaBr

20. Calcium sulphate - Chemical formula of Calcium sulphate is NaBr.
The formula is obtain as follows –
Symbol of Calcium is - Ca &
Symbol of Sulphate is – So4

21. Now,
The valency of Calcium is +2
& The valency of Sulphate is -2.
Cross multiply the valencies
Ca So4
The formula of Calcium Sulphate
is CaSo4