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

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

Matter Solid Liquid Gaseous

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

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

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.

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.”

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

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

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

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

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

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

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

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

Chemical formulae of compounds

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.

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

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

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