Atoms and Molecules

Question 1 Which Indian philosopher suggested that all matter is composed of ver small particles. What name was given by him to these particles?

Question 2 What is law of conservation of mass? Give example?

Question 3 What is meant by law of constant proportion? Give example?

Question 4 Name the scientist who gave law of conservation of mass?

Question 5 Name the scientist who gave law of constant proportion?

Question 6 Hydrogen and oxygen combine in the ratio 1:8 by mass to form water. What mass of oxygen gas would be requires to react completely with 3g of hydrogen gas?

Question 7 Copper sulphate react with sodium hydroxide to form a copper hydroxide and sodium sulphate. In an experiment,15.95 g of copper sulphate reacted with 8 g of sodium hydroxide to form 9.75g of copper hydroxide and 14.2 g of sodium sulphate. Show that this data verifies law of conservation of mass.

Question 8 When 5 g of calcium in burnt in 2 g of oxygen, then 7 g of calcium oxide is produced. What mass of calcium oxide will be produced when 5 g of calcium is burnt in 20 g of oxygen? Which law of chemical combination will govern your answer?

Atoms and Molecule

Matter is called Padarth in hindi.

Maharishi kanad,said that if we go on dividing matter,we will get smaller and smaller particles of matter.Ultimately,we will get the smallest particle of matter,which cannot be divided any further.He was the first person to propose that matter is made up of very small particles called parmanu.

John Dalton called these particles as atoms.The word atom means indivisible.

Combined form of atoms is called as molecules.

All the matter is made up of small particles called atoms and molecules.

Different kinds of atoms and molecules have different properties due to which different kinds of matter also show different properties.

The properties of matter depend on the properties of atoms and molecules from which it is made.

Laws of Chemical Combination

(1) Law of Conservation of Mass

(2) Law of Constant Proportion

Law of Conservation of Mass

Law of Conservation of Mass was given by LAVOISIER in 1774.

According to the Law of Conservation of Mass matter is neither created nor destroyed in a chemical reaction.

The substances which combine together in a chemical reaction are called Reactants.

The new substances formed as a result of chemical reaction are called as Products.

The total mass of reactants is equal to total mass of products.

For Example: When 100g of calcium carbonate is heated in a chemical reaction then
56g of calcium oxide and 44g of carbon dioxide are formed.

The total mass of product is equal to the total mass of the reactants,there is no change of mass during this chemical reaction.The mass remains the same or conserved.

Law of Constant Proportion

The Law of Constant Proportion was given by PROUST in 1779.

According to Law of Constant Proportion “A chemical compound always consist of same elements combined together in the same proportion by mass.”

For Example: Water is a compound which always consist of hydrogen and oxygen combined together in the same proportion of 1:8 by mass.